Eating Well

Our assessments of evidence for each medical benefit fall into one of these categories:

• Strong evidence: consistent, significant effects in several large (or at least one very large) well designed clinical studies or at least two meta-analysesa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of clinical studies of moderate or better quality (or one large meta-analysis) finding similar results
• Good evidence: significant effects in one large or several mid-sized and well-designed clinical studies ( randomized controlled trialsa study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects with an appropriate placebo or other strong comparison control or observational studies that control for confounds)
• Modest evidence: significant effects in at least three small but well-designed randomized controlled trials (RCTs), or one or more well-designed, mid-sized clinical studies of reasonably good quality (RCTs or observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies), or several small studies aggregated into a meta-analysis
• Preliminary evidence: significant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect
• Weak evidence: one or more case studies, supported by animal evidence OR small treatment effects of limited clinical significance OR studies with no controls OR weak trends of effects
• Insufficient evidence: preclinical evidence only OR clinical studies with such poor or unclear methodology that no conclusion can be drawn OR conflicting findings across clinical studies with no preponderance of evidence in one direction; conflicting evidence occurs when studies find conflicting effects (positive effect vs no effect or negative effect) with the same treatment and the same general study population (same cancer type, for example)

• Higher survival among people with cancer with adherence to the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) lifestyle recommendations for cancer prevention and health outcomes compared to other people in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 2 observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies¹Solans M, Chan DSM, Mitrou P, Norat T, Romaguera D. A systematic review and meta-analysis of the 2007 WCRF/AICR score in relation to cancer-related health outcomes. Annals of Oncology. 2020 Mar;31(3):352-368.

Recommended eating patterns: good evidence of longer survival and in some cases fewer events such as metastases among people reducing dietary fat, increasing fruits and vegetables, and other healthy eating patterns

• A 15% lower mortality from all causes after a breast cancer diagnosis among people following a diet low in fat and high in fruits and vegetables compared to those following their usual diets in a very large randomized trial²Prentice RL, Aragaki AK et al. Low-fat dietary pattern among postmenopausal women influences long-term cancer, cardiovascular disease, and diabetes outcomes. Journal of Nutrition. 2019 Jun 8. pii: nxz107.
• Better survival after breast cancer diagnosis among people reducing fat to 20% of total calories and increasing amounts of vegetables, fruits, and grains compared to other people in a large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study following women for 19 years³Chlebowski RT, Aragaki AK et al. Dietary modification and breast cancer mortality: long-term follow-up of the Women’s Health Initiative randomized trial. Journal of Clinical Oncology. 2020;38(13):1419‐1428.
• Lower breast cancer-specific and all-cause mortality among women who more closely followed a diabetes risk-reduction diet both before and after a diagnosis of breast cancer compared with women with less healthy diets or those who did not substantially modify what they ate following diagnosis in 2 large observational studies⁴Osterweil N. Diabetes prevention diet may lower mortality risk in breast cancer. Medscape Oncology. December 10, 2020. Viewed December 14, 2020; Wang T, Farvid M et al. Publication Number: GS2-09. Diabetes risk reduction diet and survival following breast cancer. 2020 San Antonio Breast Cancer Symposium. Viewed December 14, 2020.
• Lower mortality among women with metastatic cancer with higher consumption of vegetables, carotenoids (found in carrots, squash, mango, cantaloupe, sweet potatoes and tomatoes), and fiber compared to other women, but no evidence of an effectoverall, one or more studies did not demonstrate that a treatment or intervention led to an expected outcome; this does not always mean that there is no effect in clinical practice, but that the studies may have been underpowered (too few participants) or poorly designed. Larger, well-designed studies provide more confidence in making assessments. among women with nonmetastatic cancer, in a very large observational study⁵Pierce JP. Diet and breast cancer prognosis: making sense of the Women’s Healthy Eating and Living and Women’s Intervention Nutrition Study trials. Current Opinions in Obstetrics & Gynecology. 2009 Feb;21(1):86-91.

Soy foods: modest evidence of better survival among people with breast cancer eating soy foods

Current evidence does not support previous assertions that soy isoflavones might worsen breast cancer outcomes, with recommendations to avoid soy foods. Some outcomes are specific to the types of breast cancer studied or the treatment used. The potential benefit may be limited to people with both estrogen receptor negative (ER-) and progesterone receptor negative (PR-) tumors or those who are not receiving hormone therapy.

• A 15–24% lower mortality with breast cancer eating soy foods, and especially tofu, compared to other people in several large observational studies;⁶Wang Q, Liu X, Ren S. Tofu intake is inversely associated with risk of breast cancer: a meta-analysis of observational studies. PLoS One. 2020 Jan 7;15(1):e0226745; Zhang FF, Haslam DE et al. Dietary isoflavone intake and all-cause mortality in breast cancer survivors: the Breast Cancer Family Registry. Cancer. 2017 Jun 1;123(11):2070-2079; Chi F, Wu R, Zeng YC, Xing R, Liu Y, Xu ZG. Post-diagnosis soy food intake and breast cancer survival: a meta-analysis of cohort studies. Asian Pacific Journal of Cancer Prevention. 2013;14(4):2407-12; Caan BJ, Natarajan L et al. Soy food consumption and breast cancer prognosis. Cancer Epidemiology, Biomarkers & Prevention. 2011 May;20(5):854-8. this benefit was limited to women who had tumors that were negative for hormone receptors and those who did not receive hormone therapy for their breast cancer in one analysis⁷Zhang FF, Haslam DE et al. Dietary isoflavone intake and all-cause mortality in breast cancer survivors: the Breast Cancer Family Registry. Cancer. 2017 Jun 1;123(11):2070-2079. but not in another⁸Chi F, Wu R, Zeng YC, Xing R, Liu Y, Xu ZG. Post-diagnosis soy food intake and breast cancer survival: a meta-analysis of cohort studies. Asian Pacific Journal of Cancer Prevention. 2013;14(4):2407-12.
• A weak trendan apparent change due to a therapy, close to but not achieving full statistical significance (this is the CancerChoices definition; other researchers and studies may define this differently) toward a reduced breast cancer-specific mortality among people eating soy food amounts of 10 mg/day or more after diagnosis compared to less consumption in a large observational study⁹Nechuta SJ, Caan BJ et al. Soy food intake after diagnosis of breast cancer and survival: an in-depth analysis of combined evidence from cohort studies of US and Chinese women. American Journal of Clinical Nutrition. 2012 Jul;96(1):123-32.

Foods high in plant lignans or fiber: good evidence of better survival among postmenopausal women eating higher levels

• 48% lower overall mortality among postmenopausal women with breast cancer with the highest estimated dietary fiber intake compared to the lowest in a very large observational study¹⁰Buck K, Zaineddin AK et al. Estimated enterolignans, lignan-rich foods, and fibre in relation to survival after postmenopausal breast cancer. British Journal of Cancer. 2011 Oct 11;105(8):1151-7.
• 40% lower mortality among postmenopausal women with breast cancer who had higher levels of enterolactone (a lignan metabolite) or fiber (estimated from diet) compared to low levels in a large observational study¹¹Buck K, Zaineddin AK et al. Estimated enterolignans, lignan-rich foods, and fibre in relation to survival after postmenopausal breast cancer. British Journal of Cancer. 2011 Oct 11;105(8):1151-7.
• 44% lower cancer-specific mortality among postmenopausal women with breast cancer who had higher levels (>20.5 nmol/l) of enterolactone before diagnosis compared to lower levels in a mid-sized observational study¹²Olsen A, Christensen J, et al. Prediagnostic plasma enterolactone levels and mortality among women with breast cancer. Breast Cancer Research and Treatment. 2011;128:883-889.
• Lower all-cause and breast cancer-specific mortality among women with early breast cancer with enterolactone levels ≥ 10 nmol/l compared to lower levels in a mid-sized observational study¹³Guglielmini P, Rubagotti A, Boccardo F. Serum enterolactone levels and mortality outcome in women with early breast cancer: a retrospective cohort study. Breast Cancer Research and Treatment. 2012;132:661-668.

Flaxseed: preliminary evidence of anticancer action of flaxseed among postmenopausal women with breast cancer (details in Flaxseed ›)

Coffee: preliminary evidence of better survival and reduced risk of early events among people drinking coffee

• Significantly lower risk of early events, including death attributed to breast cancer, among people with estrogen receptor positive (ER+) tumors treated with tamoxifen when drinking 2 or more cups of coffee per day compared to those with low amounts in a mid-sized observational study; the proportion of ER- tumors increased with increasing coffee amounts in a mid-sized observational study¹⁴Simonsson M, Söderlind V et al. Coffee prevents early events in tamoxifen-treated breast cancer patients and modulates hormone receptor status. Cancer Causes & Control. 2013 May;24(5):929-40.

Modest evidence of higher mortality among people with ER-positive tumors and those with higher body mass index (BMI) drinking sugar-sweetened soda beverages

Higher mortality (both overall and cancer-specific) among people with ER-positive but not ER-negative tumors, and among women with higher body mass indices (BMIs) frequently consuming sugar-sweetened soda beverages compared to those with little or no consumption in a large observational study; overall mortality was higher among premenopausal but not postmenopausal women with higher amounts of sugar-sweetened beverages in a mid-sized observational study¹⁵Koyratty N, McCann SE et al. Sugar-sweetened soda consumption and total and breast cancer mortality: the Western New York Exposures and Breast Cancer (WEB) Study. Cancer Epidemiology, Biomarkers & Prevention. 2021 Mar 2:cebp.1242.2020.

Recommended diet pattern: modest evidence of moderately better survival and lower risk of metastasis among people following the recommended diet

• 42% lower mortality at 5 years among people with colorectal cancer who followed the American Cancer Society guidelines most closely compared to those who followed the guidelines the least in a mid-sized observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study¹⁶Van Blarigan EL, Fuchs CS et al. Association of survival with adherence to the American Cancer Society Nutrition and Physical Activity Guidelines for Cancer Survivors after colon cancer diagnosis: The CALGB 89803/Alliance Trial. JAMA Oncology. 2018 Apr 12.
• Higher risk of metastasis and death among people with colorectal cancer with Western dietary patterns such as eating large amounts of processed meats and refined grains and low quantities of vegetables and fruits—the Standard American diet, or SAD—compared to those eating the inverse in mid-sized¹⁷Zhu Y, Wu H et al. Dietary patterns and colorectal cancer recurrence and survival: a cohort study. BMJ Open. 2013 Feb 7;3(2). pii: e002270 and large¹⁸Meyerhardt JA, Niedzwiecki D et al. Association of dietary patterns with cancer recurrence and survival in patients with stage III colon cancer. Journal of the American Medical Association. 2007 Aug 15;298(7):754-64. observational studies

Tree nuts: preliminary evidence of better survival among people eating tree nuts

• 57% lower mortality among people with stage 3 colon cancer who were treated with surgery and adjuvant chemotherapy and who ate 2 or more weekly servings of tree nuts compared to those eating no nuts in a mid-sized observational study¹⁹Fadelu T, Zhang S et al. Nut consumption and survival in patients with stage III colon cancer: results from CALGB 89803 (Alliance). Journal of Clinical Oncology. 2018 Feb 28:JCO2017755413.

• 25% lower overall mortality among people with head and neck cancer with the highest vegetable intake before diagnosis compared to the lowest levels in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 4 observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies²⁰Hurtado-Barroso S, Trius-Soler M, Lamuela-Raventós RM, Zamora-Ros R. Vegetable and fruit consumption and prognosis among cancer survivors: a systematic review and meta-analysis of cohort studies. Advances in Nutrition. 2020 Nov 16;11(6):1569-1582.
• Almost 45% lower mortality over several years among people with head and neck cancer eating a whole-foods diet (high amounts of vegetables, fruit, fish, poultry, and whole grains) before treatment compared to those with a pattern of high amounts of red and processed meats, refined grains, potatoes, and French fries in a mid-sized observational study²¹Arthur AE, Peterson KE et al. Pretreatment dietary patterns, weight status, and head and neck squamous cell carcinoma prognosis. The American Journal of Clinical Nutrition, 97(2):360-368.

• Better survival among women with invasive epithelial ovarian cancer with the highest compared with lowest consumption of fiber, green, leafy vegetables, fish, and higher ratio of poly- to monounsaturated fats before diagnosis, and worse survival among those eating higher glycemic index foods in a mid-sized observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study²²Playdon MC, Nagle CM et al. Pre-diagnosis diet and survival after a diagnosis of ovarian cancer. British Journal of Cancer. 2017 Jun 6;116(12):1627-1637.
• A weak trend lower overall mortality among people with ovarian cancer with the highest vegetable intake before diagnosis compared to the lowest levels in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 5 observational studies²³Hurtado-Barroso S, Trius-Soler M, Lamuela-Raventós RM, Zamora-Ros R. Vegetable and fruit consumption and prognosis among cancer survivors: a systematic review and meta-analysis of cohort studies. Advances in Nutrition. 2020 Nov 16;11(6):1569-1582.

Cruciferous vegetables (broccoli family): modest evidence of less cancer progression among people eating more cruciferous vegetables

• 59% decreased risk of prostate cancer progression among men consuming the highest levels of cruciferous vegetables after diagnosis compared to the lowest levels in a large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study²⁴Richman EL, Carroll PR, Chan JM. Vegetable and fruit intake after diagnosis and risk of prostate cancer progression. International Journal of Cancer. 2012 Jul 1;131(1):201-10.

Low-carbohydrate diet: preliminary evidence of better treatment effects among people eating a low-carbohydrate diet

• Slightly lower androgen levels beyond those achieved with androgen deprivation therapy (ADT) among men following a low-carbohydrate diet compared to no change in diet in a multicenter RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects²⁵Chi JT, Lin PH et al. The influence of low-carbohydrate diets on the metabolic response to androgen-deprivation therapy in prostate cancer. Prostate. 2021 Jul;81(10):618-628.

Fats: preliminary evidence of less cancer proliferation among people eating a low-fat diet and taking omega-3 supplements

• Less prostate cancer proliferation and benign and malignant prostate tissue among men undergoing radical prostatectomy taking omega-3 (fish oil) supplements and following a low-fat diet compared to a control (Western) diet in a small RCT²⁶Aronson WJ , Kobayashi N et al. Phase II prospective randomized trial of a low-fat diet with fish oil supplementation in men undergoing radical prostatectomy. Cancer Prevention Research (Phila). 2011 Dec;4(12):2062-71.

Meat and eggs: Preliminary evidence of increased risk of progression among people eating eggs or poultry with skin, but no evidence of an effect with other types of meat

• Double the risk of progression among people with prostate cancer eating the highest amounts of eggs or poultry with skin compared to the lowest, but no evidence of an effect of eating processed and unprocessed red meat, fish, total poultry, and skinless poultry in a large observational study²⁷Richman EL, Stampfer MJ et al. Intakes of meat, fish, poultry, and eggs and risk of prostate cancer progression. American Journal of Clinical Nutrition. 2010 Mar;91(3):712-21.

Low-polyamine diet; foods high in polyamine were eliminated, including mushrooms, peas, hazelnuts, pistachios, spinach, broccoli, cauliflower, and green beans: preliminary evidence of substantially longer survival among people with hormone-refractory prostate cancer following a diet low in polyamine-containing foodstuffs and partial gut decontamination

• Substantially longer survival—36 vs 17 months—among people with hormone-refractory prostate cancer following a diet low in polyamine-containing foodstuffs and partial gut decontamination with oral neomycin or nifuroxazide compared to controls in a small controlled trial²⁸Cipolla BG, Havouis R, Moulinoux JP. Polyamine reduced diet (PRD) nutrition therapy in hormone refractory prostate cancer patients. Biomedicine & Pharmacotherapy. 2010 May;64(5):363-8.

Pomegranate juice: weak evidence of longer prostate specific antigen (PSA) doubling time among people drinking pomegranate juice

• Longer prostate specific antigen (PSA) doubling time among people with prostate cancer with rising PSA after surgery or radiotherapy who consumed pomegranate juice compared to baseline in a small uncontrolled triala study in which a therapy is used, but without a comparison group against which to judge outcomes; an uncontrolled trial is considered a weak study design²⁹Pantuck AJ, Leppert JT et al. Phase II study of pomegranate juice for men with rising prostate-specific antigen following surgery or radiation for prostate cancer. Clinical Cancer Research. 2006 Jul 1;12(13):4018-26.

Tomato-based foods: weak evidence of PSA stabilization eating more tomato-based foods and taking soy supplements

• Lower PSA levels among 14 of 41 men (34%) with prostate cancer with rising serum PSA following local therapy or while on hormone therapy who increased consumption of tomato products and soy supplements for 8 weeks compared to baseline in a small uncontrolled trial³⁰Grainger EM, Schwartz SJ et al. A combination of tomato and soy products for men with recurring prostate cancer and rising prostate specific antigen. Nutrition and Cancer. 2008;60(2):145-54.

• Better anticoagulant activity among people with cancer receiving a diet with additional amounts of garlic, onion, tomato, shiitake, rice bran, kale, blueberry, pineapples, and/or turmeric powder for people in remission, plus an addition 0.5 serving of protein for people receiving chemotherapy, compared to baseline in an uncontrolled trial³¹Lee GY, Lee JJ, Lee SM. Antioxidant and anticoagulant status were improved by personalized dietary intervention based on biochemical and clinical parameters in cancer patients. Nutrition and Cancer. 2015;67(7):1083-92.

Insulin is naturally highest between noon and 6:00 pm.³²Boden G, Ruiz J, Urbain JL, Chen X. Evidence for a circadian rhythm of insulin secretion. American Journal of Physiology. 1996 Aug;271(2 Pt 1):E246-52. Consuming your largest meal then may help balance levels.³³Block KI. Life over Cancer: The Block Center Program for Integrative Cancer Care. New York: Bantam Dell. 2009.

High-calorie foods: strong evidence of higher risk of type 2 diabetes among people eating high calorie (energy-dense) foods

• Higher risk of type 2 diabetes among people eating energy-dense foods compared to other people in a meta-analysis of 47 systematic reviews and 11 meta-analyses³⁴Bazshahi E, Sheikhhossein F, Amini MR, Shab-Bidar S. The association of dietary energy density and the risk of obesity, type 2 diabetes and metabolic syndrome: a systematic review and meta-analysis of observational studies. International Journal of Clinical Practice. 2021 May 1:e14291.

Legumes: good evidence of better fasting blood glucose and insulin among people eating legumes

• Lower fasting blood glucose and insulin among people both with and without diabetes eating non-oil-seed pulses (chickpeas, beans, peas, lentils, etc.) compared to other people in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 11 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects³⁵Sievenpiper JL, Kendall CW et al. Effect of non-oil-seed pulses on glycaemic control: a systematic review and meta-analysis of randomised controlled experimental trials in people with and without diabetes. Diabetologia. 2009 Aug;52(8):1479-95.

Low-carbohydrate diet: modest evidence of better blood sugar balance, insulin levels, and markers of metabolism among people eating a low-carbohydrate diet

• Better blood sugar balance (lower HbA1c, with high-certainty evidence) and in some cases insulin levels among people eating foods with a low glycemic index compared to controls in meta-analysis of 29 RCTs³⁶Harvard TH Chan School of Public Health. Carbohydrates and Blood Sugar. Viewed May 7, 2021; Chiavaroli L, Lee D et al. Effect of low glycaemic index or load dietary patterns on glycaemic control and cardiometabolic risk factors in diabetes: systematic review and meta-analysis of randomised controlled trials. BMJ. 2021 Aug 4;374:n1651.
• Better blood sugar balance and markers of metabolism among men undergoing androgen deprivation therapy (ADT) with a low-carbohydrate diet compared to no change in diet in a multicenter RCT³⁷Chi JT, Lin PH et al. The influence of low-carbohydrate diets on the metabolic response to androgen-deprivation therapy in prostate cancer. Prostate. 2021 Jul;81(10):618-628.

Foods high in inositol hexaphosphate: preliminary evidence of lower insulin resistance among people with type 2 diabetes eating a diet high in inositol hexaphosphate

• Lower markers of blood glucose levels after 12 weeks of a diet high in inositol hexaphosphate among people with type 2 diabetes compared to baseline in a small controlleda study design in which people are assigned to either an experimental group or a control group to compare the outcomes from different treatment; assignment is not random, and so this is not as strong a study design as a randomized controlled trial, but still stronger than an uncontrolled trial trial³⁸Sanchis P, Rivera R et al. Phytate decreases formation of advanced glycation end-products in patients with type II diabetes: randomized crossover trial. Scientific Reports. 2018 Jun 25;8(1):9619.

Foods high in carotenoids and lycopene: preliminary evidence of lower markers of insulin resistance or metabolic syndrome among people eating foods rich in carotenoids and especially lycopene, but not after only 4 weeks

• Lower prevalence of metabolic syndrome among middle-aged and elderly men with higher consumption of foods rich in carotenoids or lycopene compared to the lowest consumption in a small observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study³⁹Sluijs I, Beulens JW, Grobbee DE, van der Schouw YT. Dietary carotenoid intake is associated with lower prevalence of metabolic syndrome in middle-aged and elderly men. Journal of Nutrition. 2009 May;139(5):987-92.
• Lower insulin resistance people with metabolic syndrome following a 12-month intervention of drinking tomato juice 4 times a week compared to controls in a small RCT⁴⁰Tsitsimpikou C, Tsarouhas K et al. Dietary supplementation with tomato-juice in patients with metabolic syndrome: a suggestion to alleviate detrimental clinical factors. Food and Chemical Toxicology. 2014 Dec;74:9-13.
• No change in inflammatory markers among healthy, moderately overweight, middle-aged people after 4 weeks of high consumption of tomato-based foods compared to controls on a low-tomato diet in a small RCT⁴¹Thies F, Masson LF et al. Effect of a tomato-rich diet on markers of cardiovascular disease risk in moderately overweight, disease-free, middle-aged adults: a randomized controlled trial. American Journal of Clinical Nutrition. 2012 May;95(5):1013-22.

Green tea: modest evidence of lower markers of blood sugar and insulin resistance among a general population drinking green tea, but not among people with prediabetes or type 2 diabetes

• Lower fasting glucose and glycated hemoglobin (HbA1c), plus insulin (among higher quality studies), among people drinking green tea or taking green tea extract compared to controls in a meta-analysis of 17 RCTs⁴²Liu K, Zho]u R et al. Effect of green tea on glucose control and insulin sensitivity: a meta-analysis of 17 randomized controlled trials. American Journal of Clinical Nutrition. 2013 Aug;98(2):340-8.
• No change in markers of blood sugar, fasting insulin, or fasting glucose among people with prediabetes or type 2 diabetes drinking green or or taking green tea extract compared to placebos in a meta-analysis of 6 RCTs⁴³Yu J, Song P, Perry R, Penfold C, Cooper AR. The effectiveness of green tea or green tea extract on insulin resistance and glycemic control in type 2 diabetes mellitus: a meta-analysis. Diabetes & Metabolism Journal. 2017 Aug;41(4):251-262.

Small, frequent meals: preliminary evidence of lower levels of an insulin-like growth factor, a biomarker linked to increased cancer risk, among people eating 8 small meals per day compared to 3

• Lower serum IGF-1 among people eating 8 small meals per day compared to 3 in a small RCT⁴⁴Perrigue MM, Drewnowski A et al. Randomized trial testing the effects of eating frequency on two hormonal biomarkers of metabolism and energy balance. Nutrition and Cancer. 2017 Jan;69(1):56-63.

• More weight loss and less weight gain among people with body-mass index (BMI) >25 eating more fruits and vegetables compared to lower levels in a meta-analysis of 17 controlled trials⁴⁵Arnotti K, Bamber M. Fruit and vegetable consumption in overweight or obese individuals: a meta-analysis. Western Journal of Nursing Research. 2020 Apr;42(4):306-314.
• No evidence of an effect on obesity among people eating energy-dense foods compared to other people in a meta-analysis of 47 systematic reviews and 11 meta-analyses⁴⁶Bazshahi E, Sheikhhossein F, Amini MR, Shab-Bidar S. The association of dietary energy density and the risk of obesity, type 2 diabetes and metabolic syndrome: a systematic review and meta-analysis of observational studies. International Journal of Clinical Practice. 2021 May 1:e14291.

Hormone balance: modest evidence of better hormone balance among people eating the recommended dietary patterns or eating fewer calories

• Better hormone balance among people following the recommended dietary patterns compared to other people in a review⁴⁷Marks V. How our food affects our hormones. Clinical Biochemistry. 1985 Jun;18(3):149-53.

Preliminary evidence of higher levels of  1 biomarker of stress (the enzyme alpha-amylase), although no effect on another biomarker (salivary cortisol), among people drinking caffeine

• Higher levels of alpha-amylase but no change in salivary cortisol among people drinking coffee with caffeine compared to no coffee in a small RCT⁴⁸Papakonstantinou E, Kechribari I et al. Acute effects of coffee consumption on self-reported gastrointestinal symptoms, blood pressure and stress indices in healthy individuals. Nutrition Journal. 2016 Mar 15;15:26.

Preliminary evidence of maintained levels of the hormone melatonin and also of the enzyme tryptophan among people with lung cancer during chemotherapy with an amino acid nutritional intervention; both melatonin and tryptophan are involved in sleep quality

• Less reduction of serum tryptophan and melatonin levels among people with non-small cell lung cancer receiving chemotherapy treated with either 250 or 500 ml per day amino acid parenteraloccurring outside the intestine, such as parenteral nutrition given through a vein (intravenously) nutritional support compared to controls, and higher levels among those receiving 500 ml compared to 250 ml in a small RCT⁴⁹Yin S, Hu SL et al. [The effect of amino acid nutritional support on serum tryptophan and melatonin in lung cancer patients receiving chemotherapy]. Zhonghua Zhong Liu Za Zhi. 2006 Nov;28(11):840-3. Chinese.

Melatonin ›

Some foods and dietary patterns are naturally inflammatory, while others are anti-inflammatory:⁵⁰Bhargava, HD. Natural Anti-Inflammatory Diet. Nourish by WebMD. August 11, 2020. Viewed April 22, 2021; Norde MM, Collese TS, Giovannucci E, Rogero MM. A posteriori dietary patterns and their association with systemic low-grade inflammation in adults: a systematic review and meta-analysis. Nutrition Reviews. 2021 Feb 11;79(3):331-350; Jahns L, Conrad Z et al. A diet high in carotenoid-rich vegetables and fruits favorably impacts inflammation status by increasing plasma concentrations of IFN-α2 and decreasing MIP-1β and TNF-α in healthy individuals during a controlled feeding trial. Nutrition Research. 2018 Apr;52:98-104; Galland L. Diet and inflammation. Nutrition in Clinical Practice. 2010 Dec;25(6):634-40; Kopf JC, Suhr MJ et alJ. Role of whole grains versus fruits and vegetables in reducing subclinical inflammation and promoting gastrointestinal health in individuals affected by overweight and obesity: a randomized controlled trial. Nutrition Journal. 2018 Jul 30;17(1):72; Oliveira A, Rodríguez-Artalejo F, Lopes C. The association of fruits, vegetables, antioxidant vitamins and fibre intake with high-sensitivity C-reactive protein: sex and body mass index interactions. European Journal of Clinical Nutrition. 2009 Nov;63(11):1345-52.

Pro-inflammatory foods:⁵¹Foods that fight inflammation. Harvard Health Publishing. November 16, 2021. Viewed January 23, 2022.

• Refined carbohydrates, such as white bread and pastries
• French fries and other fried foods
• Soda and other sugar-sweetened beverages
• Red meat (burgers, steaks) and processed meat (hot dogs, sausage)
• Margarine, shortening, and lard

Anti-inflammatory foods:

• Tomatoes
• Fruits: strawberries, blueberries, oranges, and cherries
• Nuts
• Olive oil
• Leafy greens: spinach, kale, collards, and more
• Fatty fish: salmon, mackerel, tuna, and sardines

Fermented foods: good evidence of one lower marker of inflammation (TNF-α) but not others (C-reactive protein and interleukin-6) among people eating fermented foods

• One lower marker of inflammation (TNF-α) but not others (C-reactive protein and interleukin-6) among people eating fermented foods compared to controls in a meta-analysis of 26 RCTs⁵²SaeidiFard N, Djafarian K, Shab-Bidar S. Fermented foods and inflammation: a systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition ESPEN. 2020 Feb;35:30-39.

Recommended diet pattern: modest evidence of lower obesity-related inflammation among people eating low-carbohydrate or plant-based diets

• Less obesity-related inflammation among people following plant-based diets compared to other diets in a meta-analysis of 29 intervention trialsa study design in which people are given a treatment or therapy, or directed to follow a practice⁵³Eichelmann F, Schwingshackl L, Fedirko V, Aleksandrova K. Effect of plant-based diets on obesity-related inflammatory profiles: a systematic review and meta-analysis of intervention trials. Obesity Reviews. 2016 Nov;17(11):1067-1079.

Blueberries: preliminary evidence of lower markers of inflammation among people eating freeze-dried blueberries

• Lower markers of inflammation among people with metabolic syndrome consuming 22.5 g freeze-dried blueberries twice daily for 6 weeks compared to placebo in an RCT⁵⁴Nair AR, Mariappan N, Stull AJ, Francis J. Blueberry supplementation attenuates oxidative stress within monocytes and modulates immune cell levels in adults with metabolic syndrome: a randomized, double-blind, placebo-controlled trial. Food & Function. 2017 Nov 15;8(11):4118-4128.

Blueberries: modest evidence of lower markers of oxidation and DNA damage with blueberries

• Lower markers of oxidation among people with metabolic syndrome consuming 22.5 g freeze-dried blueberries twice daily for 6 weeks compared to placebo in an RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects⁵⁵Nair AR, Mariappan N, Stull AJ, Francis J. Blueberry supplementation attenuates oxidative stress within monocytes and modulates immune cell levels in adults with metabolic syndrome: a randomized, double-blind, placebo-controlled trial. Food & Function. 2017 Nov 15;8(11):4118-4128.
• Lower markers of oxidation and DNA damage among men with risk factors for cardiovascular disease consuming a wild blueberry drink for 6 weeks compared to placebo in a small RCT⁵⁶Riso P, Klimis-Zacas D et al. Effect of a wild blueberry (Vaccinium angustifolium) drink intervention on markers of oxidative stress, inflammation and endothelial function in humans with cardiovascular risk factors. European Journal of Nutrition. 2013 Apr;52(3):949-61.
• Lower levels of oxidative DNA damage among pre- and stage 1-hypertensive postmenopausal women consuming 22 g freeze-dried highbush blueberry powder daily for 4 weeks, but no evidence of an effect at 8 weeks, compared to controls in a small RCT⁵⁷Johnson SA, Feresin RG et al. Effects of daily blueberry consumption on circulating biomarkers of oxidative stress, inflammation, and antioxidant defense in postmenopausal women with pre- and stage 1-hypertension: a randomized controlled trial. Food & Function. 2017 Jan 25;8(1):372-380.

Low-carbohydrate or Mediterranean diets: Preliminary evidence of less oxidative stress among people following low-carbohydrate and Mediterranean diets

• Less oxidative stress among people following low-carbohydrate and Mediterranean diets compared to other diets in a review of small clinical trials⁵⁸Kaushik AS, Strath LJ, Sorge RE. Dietary interventions for treatment of chronic pain: oxidative stress and inflammation. Pain and Therapy. 2020 Dec;9(2):487-498.

Preliminary evidence of less oxidation among women eating extra-virgin olive oil

• Fewer markers of oxidation among women eating extra-virgin olive oil compared to refined olive oil in a small RCT⁵⁹Rus A, Molina F, Ramos MM, Martínez-Ramírez MJ, Del Moral ML. Extra virgin olive oil improves oxidative stress, functional capacity, and health-related psychological status in patients with fibromyalgia: a preliminary study. Biological Research for Nursing. 2017 Jan;19(1):106-115.

Weak evidence of better antioxidant status among people with cancer receiving a diet with additional amounts of garlic, onion, tomato, shiitake, rice bran, kale, blueberry, pineapples, and/or turmeric powder

• Better antioxidant status among people with cancer receiving a diet with additional amounts of garlic, onion, tomato, shiitake, rice bran, kale, blueberry, pineapples, and/or turmeric powder for people in remission, plus an addition 0.5 serving of protein for people receiving chemotherapy, compared to baseline in an uncontrolled triala study in which a therapy is used, but without a comparison group against which to judge outcomes; an uncontrolled trial is considered a weak study design⁶⁰Lee GY, Lee JJ, Lee SM. Antioxidant and anticoagulant status were improved by personalized dietary intervention based on biochemical and clinical parameters in cancer patients. Nutrition and Cancer. 2015;67(7):1083-92.

• Less healthy metabolic states, at least partly due to differences in gut microbiota, among people eating a high-fat diet compared to other people in a review⁶¹Singh RK, Chang HW et al. Influence of diet on the gut microbiome and implications for human health. Journal of Translational Medicine 2017 Apr 8;15(1):73.
• Rapid and significant changes to the microbiome and immune response with changes in diet in a review of clinical studies⁶²Gopalakrishnan V, Helmink BA, Spencer CN, Reuben A, Wargo JA. The influence of the gut microbiome on cancer, immunity, and cancer immunotherapy. Cancer Cell. 2018;33(4):570‐580.

Risk of anxiety: good evidence of modestly lower risk of anxiety symptoms among people following the recommended diet patterns or a vegetarian/vegan diet, but higher risk with a pro-inflammatory dieta diet including refined carbohydrates (white bread and pastries, white rice), French fries and other fried foods, soda and other sugar-sweetened beverages, red meat (burgers, steaks) and processed meat (hot dogs, sausage), margarine, shortening, and lard

• Lower scores for anxiety or prior diagnosis of anxiety disorders among people eating a diet rich in vegetables, fruit, meat, fish, and whole grains compared to other people in large and very large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies⁶³Jacka FN, Pasco JA et al. Association of Western and traditional diets with depression and anxiety in women. American Journal of Psychiatry. 2010 Mar;167(3):305-11; McMartin SE, Jacka FN, Colman I. The association between fruit and vegetable consumption and mental health disorders: evidence from five waves of a national survey of Canadians. Preventive Medicine. 2013 Mar;56(3-4):225-30.
• Lower risk of anxiety among people following a vegan/vegetarian diet compared to other people in a large meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 13 observational studies⁶⁴Iguacel I, Huybrechts I, Moreno LA, Michels N. Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis. Nutrition Reviews. 2021 Mar 9;79(4):361-381.
• Higher scores or risk of anxiety among people eating a pro-inflammatory diet high in commercially baked goods, fried foods and fatty meats, and low in fruits and vegetables compared to other people in a very large meta-analysis of 11 observational studies⁶⁵Tolkien K, Bradburn S, Murgatroyd C. An anti-inflammatory diet as a potential intervention for depressive disorders: a systematic review and meta-analysis. Clinical Nutrition. 2019 Oct;38(5):2045-2052. and a further large observational study⁶⁶Salari-Moghaddam A, Keshteli AH, Afshar H, Esmaillzadeh A, Adibi P. Association between dietary inflammatory index and psychological profile in adults. Clinical Nutrition. 2019 Oct;38(5):2360-2368.

Symptoms of anxiety: good evidence of higher levels of anxiety symptoms among people consuming higher amounts of caffeine

• Substantially higher jitteriness among people drinking energy drinks compared to controls in a large meta-analysis of 32 observational studies⁶⁷Nadeem IM, Shanmugaraj A et al. Energy drinks and their adverse health effects: a systematic review and meta-analysis. Sports Health. 2021 May-Jun;13(3):265-277.
• Higher reported anxiety symptoms among students consuming higher amounts of caffeine compared to other people in large observational studies⁶⁸Hofmeister EH, Muilenburg JL, Kogan L, Elrod SM. Over-the-counter stimulant, depressant, and nootropic use by veterinary students. Journal of Veterinary Medical Education. 2010 Winter;37(4):403-16; Richards G, Smith A. Caffeine consumption and self-assessed stress, anxiety, and depression in secondary school children. Journal of Psychopharmacology. 2015 Dec;29(12):1236-47.
• Higher anxiety/jitteriness among people who were non-users or low users of caffeine when consuming caffeine compared to placeboa pill, medicine, or procedure—thought to be both harmless and ineffective—prescribed for the psychological benefit to the patient or as a sham treatment in a study to allow a comparison to a therapy of interest in a mid-sized RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects⁶⁹Rogers PJ, Heatherley SV, Mullings EL, Smith JE. Faster but not smarter: effects of caffeine and caffeine withdrawal on alertness and performance. Psychopharmacology (Berlin). 2013 Mar;226(2):229-40.
• Higher self-rated jitteriness among healthy adults consuming caffeine compared to placebo in a small RCT⁷⁰Rogers PJ, Smith JE, Heatherley SV, Pleydell-Pearce CW. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology (Berlin). 2008 Jan;195(4):569-77.
• Higher anxiety among people drinking coffee with caffeine compared to decaffeinated coffee in a small RCT⁷¹Brice CF, Smith AP. Effects of caffeine on mood and performance: a study of realistic consumption. Psychopharmacology (Berlin). 2002 Nov;164(2):188-92.
• No evidence of an effectoverall, one or more studies did not demonstrate that a treatment or intervention led to an expected outcome; this does not always mean that there is no effect in clinical practice, but that the studies may have been underpowered (too few participants) or poorly designed. Larger, well-designed studies provide more confidence in making assessments. on anxiety among people drinking coffee with caffeine compared to no coffee in a small RCT⁷²Papakonstantinou E, Kechribari I et al. Acute effects of coffee consumption on self-reported gastrointestinal symptoms, blood pressure and stress indices in healthy individuals. Nutrition Journal. 2016 Mar 15;15:26.

Modest evidence of little impact on reducing anxiety from diet alone

• No significant improvement in anxiety with dietary interventions in a meta-analysis of 16 RCTs⁷³Firth J, Marx W et al. The effects of dietary improvement on symptoms of depression and anxiety: a meta-analysis of randomized controlled trials. Psychosomatic Medicine. 2019 Apr;81(3):265-280
• Little impact on anxiety and/or depression among people with symptoms with dietary interventions (an effect in 8 of 17 controlled trialsa study design in which people are assigned to either an experimental group or a control group to compare the outcomes from different treatment; assignment is not random, and so this is not as strong a study design as a randomized controlled trial, but still stronger than an uncontrolled trial) in a systematic review⁷⁴Opie RS, O’Neil A, Itsiopoulos C, Jacka FN. The impact of whole-of-diet interventions on depression and anxiety: a systematic review of randomised controlled trials. Public Health Nutrition. 2015 Aug;18(11):2074-93.

Nutritional intervention during radiotherapy: modest evidence of better body composition among people with head and neck cancer undergoing radiotherapy

• Considerably better body composition with a nutritional intervention among people with head and neck cancer undergoing radiotherapy compared to controls in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 13 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects⁷⁵Bye A, Sandmael JA et al. Exercise and nutrition interventions in patients with head and neck cancer during curative treatment: a systematic review and meta-analysis. Nutrients. 2020 Oct 22;12(11):3233.

Foods high in carotenoids: preliminary evidence of less body fat with a diet high in carotenoids including lycopene

• Lower waist circumferences and visceral and subcutaneous fat mass among middle-aged and elderly men with highest consumption of foods rich in carotenoids or lycopene compared to the lowest consumption in a small observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study⁷⁶Sluijs I, Beulens JW, Grobbee DE, van der Schouw YT. Dietary carotenoid intake is associated with lower prevalence of metabolic syndrome in middle-aged and elderly men. Journal of Nutrition. 2009 May;139(5):987-92.

• Lower blood pressure among people with overweight inceasing fruit and vegetables in their diets compared to controls in a meta-analysis of 10 RCTs⁷⁷Arnotti K, Bamber MD, Brewer V. Dietary interventions and blood pressure in overweight or obese individuals: A systematic review and meta-analysis. Clinical Nutrition. 2022 Apr;41(4):1001-1012.
• Traditional risk factors for cardiovascular disease are also linked to increased risk of cancer, while a heart-healthy lifestyle is associated with a lower risk of future cancer. Factors that reduce risk (Life’s Simple 7) include eating better and reducing blood sugar.⁷⁸Lau ES, Paniagua SM et al. Cardiovascular risk factors are associated with future cancer. Journal of the American College of Cardiology: CardioOncology. 2021 Mar, 3 (1) 48–58.

Lemon balm: preliminary evidence of better cognitive performance among people eating foods containing lemon balm

• Improved mood and cognitive performance among people eating foods containing lemon balm (tea and other foods such as yogurt to which lemon balm has been added) compared to placeboa pill, medicine, or procedure—thought to be both harmless and ineffective—prescribed for the psychological benefit to the patient or as a sham treatment in a study to allow a comparison to a therapy of interest in small RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects⁷⁹Scholey A, Gibbs A et al. Anti-stress effects of lemon balm-containing foods. Nutrients. 2014 Oct 30;6(11):4805-21.

Chewing gum: weak evidence of better alertness and attention among people chewing gum

• Better alertness and attention among people chewing gum (but unable to separate out the act of chewing from ingesting ingredients such as sweeteners and flavorings in the gum) compared to controls in small RCTs⁸⁰Allen AP, Smith AP. Chewing gum: cognitive performance, mood, well-being, and associated physiology. Biomed Research International. 2015;2015:654806; Hirano Y, Onozuka M. Chewing and attention: a positive effect on sustained attention. Biomed Research International. 2015;2015:367026.

• Less dehydration among people adding electrolytes and sugar to oral fluids and reducing caffeine and alcohol compared to other people in a mid-sized observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study,⁸¹Kong AH, Mistry P et al. Analysis of hydration and antiemetics policies in preventing cisplatin-related gastrointestinal and renal toxicities in low-risk human papillomavirus positive-oropharyngeal cancer (HPV+OPC) patients undergoing chemoradiation in De-ESCALaTE trial. Journal of Clinical Oncology. 2019 May;37(15_suppl):6076. a review⁸²Krishnamurthi SS, Macaron C. Management of acute chemotherapy-related diarrhea. UpToDate. April 5, 2021. Viewed May 7, 2021. and a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 16 studies⁸³Zhang Y, Coca A et al. Caffeine and diuresis during rest and exercise: a meta-analysis. Journal of Science and Medicine in Sport. 2015 Sep;18(5):569-74.

• Substantially fewer depressive symptoms among people participating in dietary interventions generally following the recommended diet patterns (increasing vegetables and fruits, nuts, and fiber, and reducing fat, salt, sugar, and cholesterol) compared to controls among high-quality trials in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 16 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects⁸⁴Firth J, Marx W et al. The effects of dietary improvement on symptoms of depression and anxiety: a meta-analysis of randomized controlled trials. Psychosomatic Medicine. 2019 Apr;81(3):265-280.
• Slightly less depression among people with cancer with an online physical activity or diet intervention compared to controls in a meta-analysis of 24 RCTs⁸⁵Furness K, Sarkies MN, Huggins CE, Croagh D, Haines TP. Impact of the method of delivering electronic health behavior change interventions in survivors of cancer on engagement, health behaviors, and health outcomes: systematic review and meta-analysis. Journal of Medical Internet Research. 2020 Jun 23;22(6):e16112.
• Less anxiety and/or depression among people experiencing symptoms who participated in dietary interventions compared to controls in 8 of 17 controlled trialsa study design in which people are assigned to either an experimental group or a control group to compare the outcomes from different treatment; assignment is not random, and so this is not as strong a study design as a randomized controlled trial, but still stronger than an uncontrolled trial in a systematic review⁸⁶Opie RS, O’Neil A, Itsiopoulos C, Jacka FN. The impact of whole-of-diet interventions on depression and anxiety: a systematic review of randomised controlled trials. Public Health Nutrition. 2015 Aug;18(11):2074-93.
• Possibly lower depression, but insufficient evidence to draw conclusions, with a healthy dietary pattern in a review of evidence⁸⁷Bear TLK et al. The role of the gut microbiota in dietary interventions for depression and anxiety. Advances in Nutrition. 2020 Jul 1;11(4):890-907.
• Lower levels of depressive symptoms among people consuming ‘healthy’ foods compared to other people in an observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study⁸⁸El Ansari W, Adetunji H, Oskrochi R. Food and mental health: relationship between food and perceived stress and depressive symptoms among university students in the United Kingdom. Central European Journal of Public Health. 2014 Jun;22(2):90-7.
• Greater likelihood of depressive symptoms among people following a diet with a high inflammatory index compared to other people in a large observational study⁸⁹Shakya PR, Melaku YA et al. Dietary inflammatory index (DII®) and the risk of depression symptoms in adults. Clinical Nutrition. 2021 May;40(5):3631-3642.

Risk of depression

Good evidence of a higher risk of depression with a vegetarian/vegan diet

Modest evidence of higher rates of depression among people with higher sugar consumption

• Substantially higher (more than double) risk of depression among people following a vegan/vegetarian diet compared to other people in a large meta-analysis of 13 observational studies⁹⁰Iguacel I, Huybrechts I, Moreno LA, Michels N. Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis. Nutrition Reviews. 2021 Mar 9;79(4):361-381.
• Higher annual rate of depression among people with higher sugar consumption compared to other people across six countries in a large observational study⁹¹Westover AN, Marangell LB. A cross-national relationship between sugar consumption and major depression? Depression & Anxiety 2002; 16:118-20.

• Less fatigue among people eating a diet rich in fruit, vegetables, whole grains, and foods high in omega-3 fatty acids designed to address fatigue in breast cancer survivors compared to controls in a small RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects⁹²Zick SM, Colacino J et al. Fatigue reduction diet in breast cancer survivors: a pilot randomized clinical trial. Breast Cancer Research and Treatment. 2017 Jan;161(2):299-310.
• A weak trendan apparent change due to a therapy, close to but not achieving full statistical significance (this is the CancerChoices definition; other researchers and studies may define this differently) toward less fatigue among people with cancer treated with an online (eHealth) diet intervention compared to controls in a meta-analysis of RCTs⁹³Furness K, Sarkies MN, Huggins CE, Croagh D, Haines TP. Impact of the method of delivering electronic health behavior change interventions in survivors of cancer on engagement, health behaviors, and health outcomes: systematic review and meta-analysis. Journal of Medical Internet Research. 2020 Jun 23;22(6):e16112.

Modest evidence of fewer gastrointestinal symptoms, including diarrhea, constipation, and nausea and vomiting, with diets high in fiber or low in fat and lactose

• Lower incidence of diarrhea, reducing the need for diarrhea medications by nearly half by week 6, among women undergoing pelvic radiotherapy for gynecological malignancies who followed a low‐fat, low‐lactose diet compared to controls in a mid-sized RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects⁹⁴Bye A, Kaasa S, Ose T, Sundfør K, Tropé C. The influence of low fat, low lactose diet on diarrhoea during pelvic radiotherapy. Clinical Nutrition. 1992 Jun;11(3):147-53.
• Fewer gastrointestinal symptoms among people undergoing pelvic radiotherapy following a high-fiber diet compared to controls in a mid-sized RCT of low quality⁹⁵Lawrie TA, Green JT et al. Interventions to reduce acute and late adverse gastrointestinal effects of pelvic radiotherapy for primary pelvic cancers. Cochrane Database of Systematic Reviews. 2018 Jan 23;1(1):CD012529.
• Less use of laxatives, straining on defecation, painful defecation, and abdominal pain among children and adolescents with constipation (but not with cancer) consuming green banana biomass compared to controls in a small RCT⁹⁶Cassettari VMG, Machado NC, Lourenção PLTA, Carvalho MA, Ortolan EVP. Combinations of laxatives and green banana biomass on the treatment of functional constipation in children and adolescents: a randomized study. Jornal de Pediatria (Rio de Janeiro). 2019 Jan-Feb;95(1):27-33.

Moderate evidence of lower severity of esophagitis, oral mucositis and diarrhea during chemoradiotherapy among people receiving immunonutrition

• Lower severity of esophagitis, oral mucositis and diarrhea during chemoradiotherapy among people receiving immunonutrition compared to standard nutrition or placebo in a meta-analysis of 27 controlled trials⁹⁷Zheng X, Yu K et al. Effects of immunonutrition on chemoradiotherapy patients: a systematic review and meta-analysis. JPEN Journal of Parenteral and Enteral Nutrition. 2020 Jul;44(5):768-778.

Preliminary evidence of less nausea and vomiting among people drinking ginger tea

• Less chemotherapy-induced nausea, vomiting, and retching among people with gynecological cancers receiving cisplatin-based regimens and treated with ginger tea compared to controls in a mid-sized RCT⁹⁸Wazqar DY, Thabet HA, Safwat AM. A quasi-experimental study of the effect of ginger tea on preventing nausea and vomiting in patients with gynecological cancers receiving cisplatin-based regimens. Cancer Nursing. 2021 Nov-Dec 01;44(6):E513-E519.

• Reduced self-reported mild hot flashes or night sweats not related to cancer among post-menopausal women with mild symptoms, but not among those with moderate to severe symptoms, following a diet of reduced fat (≤20% of energy from fat) and increased amounts of vegetables and fruit (≥5 servings/day) and grains (≥6 servings/day) compared to controls in a subgroup of people in a large randomized trial⁹⁹Reame NK. Fat, fit, or famished? No clear answers from the Women’s Health Initiative about diet and dieting for longstanding hot flashes. Menopause. 2012 Sep;19(9):956-8.
• See Flaxseed › for details on evidence related to hot flashes

• Modest but significant improvements in pain among people with terminal cancer eating a Taiwanese tonic vegetable soup compared to those eating a regular hospital diet in a large RCT; adding analgesic herbs (peony root and licorice root) to the diet further modestly reduced pain in a large RCT¹⁰⁰Wu TH, Chiu TY et al. Effectiveness of Taiwanese traditional herbal diet for pain management in terminal cancer patients. Asia Pacific Journal of Clinical Nutrition. 2008;17(1):17-22.
• Less pain among people with mucositis of the mouth or esophagus from chemo/radiotherapy when avoiding foods and fluids that are tart, acidic, spicy, salty, or very sweet, or dry or rough foods in reviews of evidence in cancer care guidelines¹⁰¹Nutritional Guidelines for Symptom Management: Mucositis. BC Cancer Agency. August 2005. Viewed May 4, 2021; Mouth Sores and Pain. American Cancer Society. February 1, 2020. Viewed May 4, 2021; Mouth Sores or Mucositis. Cancer.Net. January 2020. Viewed May 7, 2021.
• Less pain from esophagitis due to radiation therapy to the chest among people eating a soft, bland diet in small, frequent meals and avoiding tobacco and potentially irritant foods (spicy foods, alcohol, and coffee) compared to other people in a review¹⁰²Baker S, Fairchild A. Radiation-induced esophagitis in lung cancer. Lung Cancer (Auckland). 2016 Oct 13;7:119-127.
• Less pain at 3 and 6 months among people with hormone-refractory prostate cancer following a diet low in polyamine-containing foods and partial gut decontamination with oral neomycin or nifuroxazide compared to controls in a small controlled trial¹⁰³Cipolla BG, Havouis R, Moulinoux JP. Polyamine reduced diet (PRD) nutrition therapy in hormone refractory prostate cancer patients. Biomedicine & Pharmacotherapy. 2010 May;64(5):363-8.

• Improved quality of life following radiotherapy among people with head and neck cancer treated with a nutritional intervention compared to other people in a review of 39 studies of various types¹⁰⁴Rodriguez AM, Komar A et al. A scoping review of rehabilitation interventions for survivors of head and neck cancer. Disability and Rehabilitation. 2019 Aug;41(17):2093-2107.
• Improved quality of life at 1 year among people who had undergone pelvic radiotherapy and were following a high-fiber diet compared to controls in an RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects of low quality¹⁰⁵Lawrie TA, Green JT et al. Interventions to reduce acute and late adverse gastrointestinal effects of pelvic radiotherapy for primary pelvic cancers. Cochrane Database of Systematic Reviews. 2018 Jan 23;1(1):CD012529.

Energy drinks: good evidence of substantially more insomnia among people consuming energy drinks

• Substantially more insomnia among people drinking energy drinks compared to controls in a large meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 32 observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies¹⁰⁶Nadeem IM, Shanmugaraj A et al. Energy drinks and their adverse health effects: a systematic review and meta-analysis. Sports Health. 2021 May-Jun;13(3):265-277.

Recommended eating pattern: preliminary evidence of better sleep quality among people eating a diet rich in fruit, vegetables, whole grains, and foods high in omega-3 fatty acids

• Better sleep quality among people eating a diet rich in fruit, vegetables, whole grains, and foods high in omega-3 fatty acids designed to address fatigue in breast cancer survivors compared to controls in a small RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects¹⁰⁷Zick SM, Colacino J et al. Fatigue reduction diet in breast cancer survivors: a pilot randomized clinical trial. Breast Cancer Research and Treatment. 2017 Jan;161(2):299-310.

Eating at night: preliminary evidence of poor sleep quality among people eating late in the evening or at night

• Disturbance to sleep-related hormones among people with night eating syndrome (consuming a large part of your calories in the evening and nighttime hours and reducing calorie intake in the morning) compared to other people in a small observational study¹⁰⁸Goel N, Stunkard AJ et al. Circadian rhythm profiles in women with night eating syndrome. Journal of Biological Rhythms. 2009 Feb;24(1):85-94.

Preliminary evidence of similar effects on physical markers of stress among women eating either healthy or unhealthy food choices in response to stress

• Comparable physical markers of stress among women after consuming either healthy or unhealthy comfort foods, and neither food type affected recovery of psychophysiological stress compared to no food in a mid-sized RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects; the researchers conclude that healthy comfort eating may be a good replacement for unhealthy comfort eating without sacrificing relief from stress¹⁰⁹Finch LE, Cummings JR, Tomiyama AJ. Cookie or clementine? Psychophysiological stress reactivity and recovery after eating healthy and unhealthy comfort foods. Psychoneuroendocrinology. 2019 Sep;107:26-36.

Whole-grain food with a protein: preliminary evidence of less stress among people eating a specific whole-grain food

• Fewer depressive symptoms and markers of stress among elderly people eating a whole-grain food with a protein, such as talbinah (a barley porridge cooked with milk and other ingredients) in a small RCT¹¹⁰Badrasawi MM, Shahar S, Abd Manaf Z, Haron H. Effect of Talbinah food consumption on depressive symptoms among elderly individuals in long term care facilities, randomized clinical trial. Clinical Interventions in Aging. 2013;8:279-85.

Vegan/vegetarian diet: no evidence of an effect on stress among people following a vegan/vegetarian diet in a large combined analysis of studies

• No evidence of an effect of a vegan/vegetarian diet on mental stress in a large meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 13 observational  studies¹¹¹Iguacel I, Huybrechts I, Moreno LA, Michels N. Vegetarianism and veganism compared with mental health and cognitive outcomes: a systematic review and meta-analysis. Nutrition Reviews. 2021 Mar 9;79(4):361-381.

Caffeine: preliminary evidence of higher stress among people consuming caffeine

• Lower subjective stress response and a lower marker of stress among people consuming low-caffeine green tea compared to unaltered tea in a small RCT¹¹²Unno K, Yamada H et al. Anti-stress effect of green tea with lowered caffeine on humans: a pilot study. Biological & Pharmaceutical Bulletin. 2017;40(6):902-909.

Chewing: unclassifiable evidence regarding chewing itself

• Temporary relief of stress with active chewing in a review of unspecified study types¹¹³Weijenberg RA, Lobbezoo F. Chew the pain away: oral habits to cope with pain and stress and to stimulate cognition. Biomed Research International. 2015;2015:149431; Kubo KY, Iinuma M, Chen H. Mastication as a stress-coping behavior. Biomed Research International. 2015;2015:876409.

Gastrointestinal symptoms

Preliminary evidence of fewer symptoms and pain related to irritable bowel syndrome (IBS) among people

Preliminary evidence of fewer symptoms of IBS, including abdominal pain, among people following a diet of low-FODMAP diet of foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols

• Lower overall symptom burden and abdominal pain in some people with IBS treated with specific probiotics compared to placebo in a review of 15 controlled trialsa study design in which people are assigned to either an experimental group or a control group to compare the outcomes from different treatment; assignment is not random, and so this is not as strong a study design as a randomized controlled trial, but still stronger than an uncontrolled trial¹¹⁴Hungin APS, Mitchell CR et al, European Society for Primary Care Gastroenterology. Systematic review: probiotics in the management of lower gastrointestinal symptoms—an updated evidence-based international consensus. Alimentary Pharmacology & Therapeutics. 2018 Apr;47(8):1054-1070.
• Fewer symptoms of IBS, including abdominal pain, among people following a diet of low-FODMAP diet, possibly via modulation of gut microbiota, compared to controls in reviews of controlled studies¹¹⁵Zhou SY, Gillilland M 3rd et al. FODMAP diet modulates visceral nociception by lipopolysaccharide-mediated intestinal inflammation and barrier dysfunction. Journal of Clinical Investigation. 2018 Jan 2;128(1):267-280; Nanayakkara WS, Skidmore PM, O’Brien L, Wilkinson TJ, Gearry RB. Efficacy of the low FODMAP diet for treating irritable bowel syndrome: the evidence to date. Clinical and Experimental Gastroenterology. 2016 Jun 17;9:131-42.

Neurological symptoms: preliminary evidence of lower pain scores among people with diabetes with painful peripheral neuropathy eating a low-fat, plant-based diet

• Lower pain scores among people with diabetes with painful peripheral neuropathy eating a low-fat, plant-based diet compared to controls in a small RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects¹¹⁶Bunner AE, Wells CL et al. A dietary intervention for chronic diabetic neuropathy pain: a randomized controlled pilot study. Nutrition and Diabetes. 2015 May 26;5(5):e158.

Pain

Dietary patterns: modest evidence of less chronic pain among people following the recommended dietary patterns

Fruits: preliminary evidence of less musculoskeletal pain among people eating blueberry, strawberry, and passion fruit peel extract

• Less pain among people following whole-food diets, with no single diet standing out for effectiveness among vegetarian/vegan, an omega-3 focus, and Mediterranean diets. Elimination diets, single-food changes, calorie/macronutrient restriction were similarly effective among people with chronic pain not specific to cancer in a systematic review of 43 clinical trials¹¹⁷Field R, Pourkazemi F, Turton J, Rooney K. Dietary interventions are beneficial for patients with chronic pain: a systematic review with meta-analysis. Pain Medicine. 2021 Mar 18;22(3):694-714.
• Less chronic pain among people following a low-carbohydrate diet compared to other diets in a review of small clinical trials¹¹⁸Kaushik AS, Strath LJ, Sorge RE. Dietary interventions for treatment of chronic pain: oxidative stress and inflammation. Pain and Therapy. 2020 Dec;9(2):487-498.
• Less musculoskeletal pain among people eating blueberry, strawberry, and passion fruit peel extract compared to controls in a review of 3 RCTs¹¹⁹Mendonça CR, Noll M, Castro MCR, Silveira EA. Effects of nutritional interventions in the control of musculoskeletal pain: an integrative review. Nutrients. 2020 Oct 9;12(10):3075.

Vegetables and fruits: good evidence of lower cancer mortality among people following a diet high in vegetables—but not starchy vegetables—and fruits before diagnosis

• Lower mortality from all causes and from cancer (and also from cardiovascular disease or respiratory disease) among people eating 5 servings of vegetables and fruits—or 2 servings of fruit and 3 servings of vegetables—per day compared to fewer servings in 2 large observational studies in the US and a meta-analysis of 26 further studies. Eating starchy vegetables—such as peas, corn and potatoes—and fruit juices was not linked to lower mortality in 2 very large observational studies.¹²¹Wang DD, Li Y, Bhupathiraju SN, Rosner BA et al. Fruit and vegetable intake and mortality: results from 2 prospective cohort studies of US men and women and a meta-analysis of 26 cohort studies. Circulation. 2021 Mar 1.

Inflammatory foods: good evidence of lower cancer risk among people following anti-inflammatory diets compared to pro-inflammatory diets

• 17% increased risk of cancer as a whole among people eating pro-inflammatory diets compared to the most anti-inflammatory diets in a large meta-analysis of 10 observational studies¹²²Namazi N, Larijani B, Azadbakht L. Association between the dietary inflammatory index and the incidence of cancer: a systematic review and meta-analysis of prospective studies. Public Health. 2018 Nov;164:148-156.

Chili peppers: strong evidence of lower cancer mortality among people regularly eating chili peppers

• 23% lower cancer-related mortality among people without cancer at baseline who eat chili peppers containing capsaicin regularly in a very large meta-analysis of RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects and observational studies¹²³Kaur M, Verma BR et al. P1036 – Impact of chilli-pepper intake on all-cause and cardiovascular mortality—a systematic review and meta-analysis. American Heart Association Scientific Sessions. November 13, 2020. Viewed December 7, 2020.

Fermented foods: strong evidence of lower risk of cancer among people eating fermented dairy foods

• Lower risk of cancer among people eating fermented dairy foods compared to other people in a very large meta-analysis of 61 observational studies¹²⁴Zhang K, Dai H, Liang W, Zhang L, Deng Z. Fermented dairy foods intake and risk of cancer. International Journal of Cancer. 2019 May 1;144(9):2099-2108.

Coffee: good evidence of lower cancer mortality among people drinking several cups of coffee per day

• Lower risk of cancer mortality among people drinking several cups of coffee per day compared to no coffee in a very large pooled analysis of 12 observational studies¹²⁵Shin S, Lee JE et al. Coffee and tea consumption and mortality from all causes, cardiovascular disease and cancer: a pooled analysis of prospective studies from the Asia Cohort Consortium. International Journal of Epidemiology. 2021 Sep 1:dyab161.

Mushrooms: modest evidence of moderately lower risk of cancer as a whole among people eating mushrooms

• 34% lower risk of cancer among people with the highest consumption of mushrooms compared to the lowest in a meta-analysis of 17 observational studies¹²⁶Ba DM, Ssentongo P et al. Higher mushroom consumption is associated with lower risk of cancer: a systematic review and meta-analysis of observational studies. Advances in Nutrition. 2021 Mar 16:nmab015.

Good evidence of lower risk of cancer as a whole among people eating the highest levels of olive oil

• Higher cancer mortality among people eating higher levels of saturated fat compared to other people, but lower mortality with increases in polyunsaturated fats in a very large meta-analysis of 19 observational studies¹²⁷Kim Y, Je Y, Giovannucci EL. Association between dietary fat intake and mortality from all-causes, cardiovascular disease, and cancer: a systematic review and meta-analysis of prospective cohort studies. Clinical Nutrition. 2021 Mar;40(3):1060-1070.
• Lower risk of cancer as a whole among people eating the highest levels of olive oil compared to the lowest levels in a large meta-analysis of 19 observational studies¹²⁸Psaltopoulou T, Kosti RI, Haidopoulos D, Dimopoulos M, Panagiotakos DB. Olive oil intake is inversely related to cancer prevalence: a systematic review and a meta-analysis of 13,800 patients and 23,340 controls in 19 observational studies. Lipids in Health and Disease. 2011 Jul 30;10:127.
• Lower cancer mortality among adults with obesity participating in dietary interventions targeting weight loss (usually low in fat and saturated fat) compared to controls in a meta-analysis of 8 RCTs with very low quality evidence¹²⁹Ma C, Avenell A et al. Effects of weight loss interventions for adults who are obese on mortality, cardiovascular disease, and cancer: systematic review and meta-analysis. BMJ. 2017 Nov 14;359:j4849.
• Very slight increase in cancer risk among people eating higher levels of polyunsaturated fatty acids compared to lower levels in a meta-analysis of 47 RCTs¹³⁰Hanson S, Thorpe G, Winstanley L, Abdelhamid AS, Hooper L; PUFAH group. Omega-3, omega-6 and total dietary polyunsaturated fat on cancer incidence: systematic review and meta-analysis of randomised trials. Cancer Epidemiology, Biomarkers & Prevention. 2020 Feb;29(2):288-299.

Meat: good evidence of lower risk of cancer among people eating less meat

• Lower risk of cancer over more than 11 years of follow up among people eating less meat compared to “regular meat-eaters”: 2% lower among those eating low levels of meat, 10% lower among those eating fish but not meat, and 20% lower among vegetarians in a very large observational study¹³¹Watling CZ, Schmidt JA et al. Risk of cancer in regular and low meat-eaters, fish-eaters, and vegetarians: a prospective analysis of UK Biobank participants. BMC Medicine. 2022 Feb 24;20(1):73.

Fat: good evidence of higher cancer mortality among people eating higher levels of saturated fats, but a very slight increase of cancer incidence with higher levels of polyunsaturated fatty acids (PUFAs). Our note: the group of polyunsaturated fatty acids includes both omega-3 and omega-6 fatty acids, which have different impacts on health. Research shows that a higher proportion of omega-3s to omega-6s is good for people with cancer. The study reported here did not analyze the different types of PUFAs separately, so we do not consider this evidence that higher levels of omega-3s might be harmful.

• Higher cancer mortality among people eating higher levels of saturated fat compared to others, but lower mortality with increases in polyunsaturated fats in a very large meta-analysis of 19 observational studies¹³²Kim Y, Je Y, Giovannucci EL. Association between dietary fat intake and mortality from all-causes, cardiovascular disease, and cancer: a systematic review and meta-analysis of prospective cohort studies. Clinical Nutrition. 2021 Mar;40(3):1060-1070.
• Lower risk of cancer as a whole among people eating the highest levels of olive oil compared to the lowest levels in a large meta-analysis of 19 observational studies¹³³Psaltopoulou T, Kosti RI, Haidopoulos D, Dimopoulos M, Panagiotakos DB. Olive oil intake is inversely related to cancer prevalence: a systematic review and a meta-analysis of 13,800 patients and 23,340 controls in 19 observational studies. Lipids in Health and Disease. 2011 Jul 30;10:127.
• Lower cancer mortality among adults with obesity participating in dietary interventions targeting weight loss (usually low in fat and saturated fat) compared to controls in a meta-analysis of 8 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects with very low quality evidence¹³⁴Ma C, Avenell A et al. Effects of weight loss interventions for adults who are obese on mortality, cardiovascular disease, and cancer: systematic review and meta-analysis. BMJ. 2017 Nov 14;359:j4849.
• Very slight increase in cancer risk among people eating higher levels of polyunsaturated fatty acids compared to lower levels in a meta-analysis of 47 RCTs¹³⁵Hanson S, Thorpe G, Winstanley L, Abdelhamid AS, Hooper L; PUFAH group. Omega-3, omega-6 and total dietary polyunsaturated fat on cancer incidence: systematic review and meta-analysis of randomised trials. Cancer Epidemiology, Biomarkers & Prevention. 2020 Feb;29(2):288-299.

• Lower risk of cancer among people eating fermented dairy foods compared to other people in a subgroup analysis of a very large meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 61 observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies¹³⁶Zhang K, Dai H, Liang W, Zhang L, Deng Z. Fermented dairy foods intake and risk of cancer. International Journal of Cancer. 2019 May 1;144(9):2099-2108.

Recurrence or relapse

Soy foods: Good evidence of lower risk of breast cancer recurrence among people eating soy foods after diagnosis; see Soy and Genistein ›

Fats: good evidence of lower risk of breast cancer recurrence or relapse among specific groups eating lower levels of dietary fat among specific subgroups: postmenopausal women, those with ER-negative cancer, or people with higher serum levels of trans-fatty acids

• A 24% lower risk of breast cancer recurrence among post-menopausal women who reduced dietary fat compared to controls in a large RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects¹³⁷Cheblowski RT, Blackburn GL et al. Dietary fat reduction and breast cancer outcome: interim efficacy results from the Women’s Intervention Nutrition Study. Journal of the National Cancer Institute. 2006 Dec 20;98(24):1767-76.
• Lower risk of relapse among women with breast cancer, especially among women with ER-negative breast cancer, following a reduced-fat diet compared to controls in a very large RCT¹³⁸Chlebowski RT, Blackburn G et al. Dietary fat reduction and breast cancer outcome: interim efficacy results from the Women’s Intervention Nutrition Study. Journal of the National Cancer Institute. 2006 Dec 20;98(24):1767-76.
• Moderately higher risk of breast cancer among postmenopausal women with higher serum levels of trans-fatty acids compared to lower levels, but no evidence of an effectoverall, one or more studies did not demonstrate that a treatment or intervention led to an expected outcome; this does not always mean that there is no effect in clinical practice, but that the studies may have been underpowered (too few participants) or poorly designed. Larger, well-designed studies provide more confidence in making assessments. across all women in a meta-analysis of 5 observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies¹³⁹Anjom-Shoae J, Sadeghi O, Larijani B, Esmaillzadeh A. Dietary intake and serum levels of trans fatty acids and risk of breast cancer: a systematic review and dose-response meta-analysis of prospective studies. Clinical Nutrition. 2020 Mar;39(3):755-764.

Fats, vegetables, fruits, and fiber: modest evidence of lower risk of recurrence among people without hot flashes or people taking tamoxifen eating a diet combining lower amounts of fat with higher levels of fruits, vegetables, and fiber

• No difference over 7 years in breast cancer recurrence among both pre- and post-menopausal women following a diet combining lower amounts of fat with higher levels of fruits, vegetables, and fiber compared to controls in a large RCT;¹⁴⁰Pierce JP, Natarajan L et al. Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer: the Women’s Healthy Eating and Living (WHEL) randomized trial. Journal of the American Medical Association. 2007;298(3):289–98. however, some subgroups showed reduced or raised risk:
  • Fewer distal recurrences among the subgroup of people without hot flashes at baseline eating higher amounts of vegetables, fruits, and fiber than the 5-a-day diet, as well as lower amounts of fat compared to other people¹⁴¹Pierce JP. Diet and breast cancer prognosis: making sense of the WHEL and WINS trials. Current Opinion in Obstetrics & Gynecology. 2009 Feb; 21(1): 86–91. and breast cancer events¹⁴²Gold EB, Pierce JP et al. Dietary pattern influences breast cancer prognosis in women without hot flashes: the women’s healthy eating and living trial. Journal of Clinical Oncology. 2009 Jan 20;27(3):352-9.
  • Lower risk of recurrence among the subgroup of people on tamoxifen eating increased amounts of vegetables, especially cruciferous vegetables (broccoli family) compared to other people¹⁴³Lemanne D, Maizes V. Advising women undergoing treatment for breast cancer: a narrative review. Journal of Alternative and Complementary Medicine. 2018 Sep/Oct;24(9-10):902-909.

Carbohydrates: preliminary evidence of much higher risk of recurrence among postmenopausal women who are insulin-like growth factor-I (IGFI) receptor positive and who do not reduce carbohydrates after diagnosis

• A fivefold increased risk of recurrence among women who are insulin-like growth factor-I (IGFI) receptor positive and who did not reduce levels of carbohydrates after a postmenopausal breast cancer diagnosis compared to other people in a mid-sized observational study¹⁴⁴Emond JA, Pierce JP et al. Risk of breast cancer recurrence associated with carbohydrate intake and tissue expression of IGFI receptor. Cancer Epidemiology, Biomarkers & Prevention. 2014 Jul;23(7):1273-9.

Cancer risk

Mushrooms: good evidence of moderately lower risk of breast cancer among people eating mushrooms

• 3% lower risk of breast cancer with each 1g per day increased consumption of mushrooms, with even lower risk among postmenopausal women, in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 10 observational studies¹⁴⁵Li J, Zou L et al. Dietary mushroom intake may reduce the risk of breast cancer: evidence from a meta-analysis of observational studies. PLoS One. 2014 Apr 1;9(4):e93437.
• 35% lower risk of breast cancer among people with the highest consumption of mushrooms compared to the lowest in a meta-analysis of 17 observational studies¹⁴⁶Ba DM, Ssentongo P et al. Higher mushroom consumption is associated with lower risk of cancer: a systematic review and meta-analysis of observational studies. Advances in Nutrition. 2021 Mar 16:nmab015.

Foods high in plant lignans or fiber: good evidence of lower risk of breast cancer among postmenopausal women eating foods high in lignans

• A weak trend toward lower risk of breast cancer overall, but a significant reduced risk of breast cancer among postmenopausal women eating foods high in lignans compared to lower levels in a pooled analysis of 21 observational studies¹⁴⁷Buck K, Zaineddin AK, Vrieling A, Linseisen J, Chang-Claude, J. Meta-analyses of lignans and enterolignans in relation to breast cancer risk. American Journal of Clinical Nutrition. 2010;92:141-153. and a meta-analysis of 11 observational studies¹⁴⁸Velentzis LS, Cantwell MM, et al. Lignans and breast cancer risk in pre- and post-menopausal women: meta-analyses of observational studies. British Journal of Cancer. 2009;100:1492-1498.
• Also see Flaxseed ›

Fat, dairy foods or calcium: strong evidence of little impact for most breast cancer types, but an increased risk of ER-negative tumors among people eating higher levels of yogurt and cottage/ricotta cheese

Good evidence of lower risk of breast cancer among people eating the highest levels of olive oil

• Lower risk of breast cancer among people eating the highest levels of olive oil compared to the lowest levels in a large meta-analysis of 19 observational studies¹⁴⁹Psaltopoulou T, Kosti RI, Haidopoulos D, Dimopoulos M, Panagiotakos DB. Olive oil intake is inversely related to cancer prevalence: a systematic review and a meta-analysis of 13,800 patients and 23,340 controls in 19 observational studies. Lipids in Health and Disease. 2011 Jul 30;10:127.
• Little impact overall on breast cancer risk of dairy foods or dietary calcium, but a 10–15% higher risk only of ER-negative tumors with higher levels of yogurt and cottage/ricotta cheese compared to low levels in a very large pooled analysis of observational studies¹⁵⁰Wu Y, Huang R et al. Dairy foods, calcium, and risk of breast cancer overall and for subtypes defined by estrogen receptor status: a pooled analysis of 21 cohort studies. American Journal of Clinical Nutrition. 2021 Aug 2;114(2):450-461.
• Slightly lower risk of breast cancer among people eating skim milk or yogurt compared to no consumption in a meta-analysis of 46 observational studies¹⁵¹Wu J, Zeng R et al. Dietary protein sources and incidence of breast cancer: a dose-response meta-analysis of prospective studies. Nutrients. 2016 Nov 17;8(11):730.
• No evidence of an effect on invasive breast cancer cancer incidence from a low-fat diet in a very large RCT¹⁵²Prentice RL, Aragaki AK et al. Low-fat dietary pattern among postmenopausal women influences long-term cancer, cardiovascular disease, and diabetes outcomes. Journal of Nutrition. 2019 Jun 8. pii: nxz107.

Red or processed meat: good evidence of slightly higher risk of breast cancer among people eating red or processed meat, and increasing risk with higher consumption

• Slightly higher risk of breast cancer among people eating either red or processed meat, with increasing risk with higher consumption, in a meta-analysis of 46 observational studies¹⁵³Wu J, Zeng R et al. Dietary protein sources and incidence of breast cancer: a dose-response meta-analysis of prospective studies. Nutrients. 2016 Nov 17;8(11):730.

Recurrence or relapse

Foods high in omega-3s, such as wild-caught salmon, mackerel, or sardines and high omega-3 eggs: modest evidence of lower risk of recurrence among people eating foods high in omega-3s

• Lower risk of recurrence (better disease-free survival) after a primary colorectal diagnosis among people eating higher amounts of foods high in omega-3s compared to low levels in a large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study¹⁵⁴Van Blarigan EL et al. Marine ω-3 polyunsaturated fatty acid and fish intake after colon cancer diagnosis and survival: CALGB 89803 (Alliance). Cancer Epidemiology, Biomarkers & Prevention. 2018 Apr;27(4):438-445.

Western diet pattern (Standard American diet—SAD): modest evidence of a substantially higher risk of recurrence among people eating large amounts of processed meats and refined grains and low quantities of vegetables and fruits

• Higher risk (82% higher in 1 study and more than doubled in the other) of tumor recurrence among people with colorectal cancer following a Western dietary pattern such as eating large amounts of processed meats and refined grains and low quantities of vegetables and fruits compared to other people in 2 mid-sized observational studies¹⁵⁵Zhu Y, Wu H et al. Dietary patterns and colorectal cancer recurrence and survival: a cohort study. BMJ Open. 2013 Feb 7;3(2). pii: e002270; Meyerhardt JA, Niedzwiecki D et al. Association of dietary patterns with cancer recurrence and survival in patients with stage III colon cancer. Journal of the American Medical Association. 2007 Aug 15;298(7):754-64.

Nuts: preliminary evidence of lower risk of recurrence among people eating tree nuts

About 40% lower risk of recurrence (better disease-free survival) among people with stage 3 colon cancer treated with surgery and adjuvant chemotherapy and eating 2 or more weekly servings of tree nuts compared to those eating no nuts in a mid-sized observational study¹⁵⁶Fadelu T, Zhang S et al. Nut consumption and survival in patients with stage iii colon cancer: results from CALGB 89803 (Alliance). Journal of Clinical Oncology. 2018 Feb 28:JCO2017755413.

Cancer risk

Researchers estimated that more than 52,000 new colorectal cancer cases in the United States in 2015 were linked to suboptimal diet among US adults.¹⁵⁷Zhang FF, Cudhea F et al. Preventable cancer burden associated with poor diet in the United States. JNCI Cancer Spectrum. 2019 May;pkz034.

Researchers think the interaction between diet and gut microbiota influences the development of colorectal cancer by changing metabolism and immune function¹⁵⁸Song M, Chan AT. Environmental factors, gut microbiota, and colorectal cancer prevention. Clinical Gastroenterology and Hepatology. 2019;17(2):275–289. Evidence supports this line of thinking:

• A high-fat diet produces secondary bile acids that change the microbiome, resulting in increased oxidation and inflammation that damage colon cells.¹⁵⁹Block KI, Block PB, Gyllenhaal C. Integrative treatment for colorectal cancer: a comprehensive approach. Journal of Alternative and Complementary Medicine. 2018;24(9-10):890–901.
• Beneficial bacteria in your gut are needed to process and create essential nutrients by fermenting dietary fiber and producing butyrate. These processes provide energy to colon cells and promote protective immune system effects. As a result, adequate dietary fiber is essential for a healthy interplay between the gut microbiome, colon cells, and immunity,¹⁶⁰Block KI, Block PB, Gyllenhaal C. Integrative treatment for colorectal cancer: a comprehensive approach. Journal of Alternative and Complementary Medicine. 2018;24(9-10):890–901. and lower levels of butyrate-producing bacteria are associated with the presence of colorectal cancer.¹⁶¹Purcell RV, Pearson J et al. Colonization with enterotoxigenic Bacteroides fragilis is associated with early-stage colorectal neoplasia. PLoS One. 2017;12(2):e0171602.

Fish and fish oils high in omega-3 fatty acids: strong evidence of lower risk among people eating higher levels of fish and fish oils high in omega-3 fatty acids

• Moderately lower risk of colorectal cancer among people with the highest intake of 2 omega-3s, DHA and EPA, from both diet and supplements in a very large meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 20 observational studies¹⁶²Kim Y, Kim J. Intake or blood levels of n-3 polyunsaturated fatty acids and risk of colorectal cancer: a systematic review and meta-analysis of prospective studies. British Journal of Cancer. 2020 Apr;122(8):1260-1270.
• Lower risk of colorectal cancer among people eating foods rich in marine omega-3 fatty acids, such as fish and fish oils in an umbrella review of meta-analyses of observational studies¹⁶³Veettil SK, Wong TY et al. Role of diet in colorectal cancer incidence: umbrella review of meta-analyses of prospective observational studies. JAMA Network Open. 2021 Feb 1;4(2):e2037341.

Fermented foods (yogurt, kefir, cultured cheese): strong evidence of lower risk of colorectal cancer among people eating fermented dairy foods as a whole (yogurt, kefir, cultured cheese)

No evidence of an effect on risk of colorectal cancer among people eating cheese in a very large combined analysis of studies

• Lower risk of cancer among people eating fermented dairy foods compared to other people in a subgroup analysis of a very large meta-analysis of 61 observational studies¹⁶⁴Zhang K, Dai H, Liang W, Zhang L, Deng Z. Fermented dairy foods intake and risk of cancer. International Journal of Cancer. 2019 May 1;144(9):2099-2108.
• No evidence of an effect on risk of colorectal cancer of eating cheese compared to no cheese in an umbrella review of meta-analyses of observational studies¹⁶⁵Veettil SK, Wong TY et al. Role of diet in colorectal cancer incidence: umbrella review of meta-analyses of prospective observational studies. JAMA Network Open. 2021 Feb 1;4(2):e2037341.

Leafy vegetables: strong evidence of lower risk of colorectal cancer among people eating dark green leafy vegetables

• Lower risk of colorectal cancer among people eating dark green leafy vegetables in an umbrella review of 45 meta-analyses of observational studies¹⁶⁶Veettil SK, Wong TY et al. Role of diet in colorectal cancer incidence: umbrella review of meta-analyses of prospective observational studies. JAMA Network Open. 2021 Feb 1;4(2):e2037341.

Calcium or fiber: good evidence of lower risk of colorectal cancer among people eating foods high in calcium or fiber

• Lower risk of colorectal serrated polyps among people eating foods high in calcium or fiber compared to other people in a meta-analysis of 43 observational or interventional studies¹⁶⁷Bailie L, Loughrey MB, Coleman HG. Lifestyle risk factors for serrated colorectal polyps: a systematic review and meta-analysis. Gastroenterology. 2017 Jan;152(1):92-104.
• Lower risk of colorectal cancer among people eating more dietary fiber, especially cereal fiber and whole grains compared to other people, in a meta-analysis of 25 observational studies¹⁶⁸Aune D, Chan DS et al. Dietary fibre, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies. BMJ. 2011 Nov 10;343:d6617.
• Lower risk of colorectal cancer among people eating foods high in calcium—such as yogurt and other dairy foods—or whole-grain foods and other foods high in dietary fiber—such as many fruits, vegetables, and legumes such as black beans, chickpeas, or lentils—in an umbrella review of meta-analyses of observational studies¹⁶⁹Veettil SK, Wong TY et al. Role of diet in colorectal cancer incidence: umbrella review of meta-analyses of prospective observational studies. JAMA Network Open. 2021 Feb 1;4(2):e2037341.

Coffee: modest evidence of lower risk of colon cancer among people drinking at least 1 cup of coffee per day

• Lower risk distal colon cancer only among people drinking at least 1 cup of coffee per day compared to no coffee in a very large observational study¹⁷⁰Nakagawa-Senda H, Ito H et al. Coffee consumption and the risk of colorectal cancer by anatomical subsite in Japan: results from the HERPACC studies. International Journal of Cancer. 2017 Jul 15;141(2):298-308.

Plant lignans: preliminary evidence of lower risk of colorectal cancer among women, but higher risk among men, and modest evidence of lower risk of colorectal adenomas

• Lower risk for colon or rectal cancers among women, but higher risk among men, with higher serum levels of enterolactone, a marker of plant lignans, in a mid-sized observational study¹⁷¹Johnsen NF, Olsen A et al. Plasma enterolactone and risk of colon and rectal cancer in a case-cohort study of Danish men and women. Cancer Causes & Control. 2010 Jan;21(1):153-62.
• Lower risk of colorectal adenomas among people with higher serum levels of enterolactone, a marker of plant lignans, in a large observational study¹⁷²Kuijsten A, Arts ICW, Hollman PCH, Veer P, Kampman E. Plasma enterolignans are associated with lower colorectal adenoma risk. Cancer Epidemiology, Biomarkers & Prevention. 2006 Jun;15(6):1132-6.
• Also see Flaxseed ›

Meat: strong evidence of higher risk of colorectal cancer among people eating red meat

• Higher risk of colorectal cancer among people eater higher levels of red meat compared to low levels in an umbrella review of meta-analyses of observational studies¹⁷³Veettil SK, Wong TY et al. Role of diet in colorectal cancer incidence: umbrella review of meta-analyses of prospective observational studies. JAMA Network Open. 2021 Feb 1;4(2):e2037341.
• 20% higher risk of colorectal cancer among people with the highest consumption of red meat compared with the lowest in a meta-analysis of 103 observational studies¹⁷⁴Huxley RR, Ansary-Moghaddam A, Clifton P, Czernichow S, Parr CL, Woodward M. The impact of dietary and lifestyle risk factors on risk of colorectal cancer: a quantitative overview of the epidemiological evidence. International Journal of Cancer. 2009 Jul 1;125(1):171-80.
• Higher risk of colorectal serrated polyps among people eating red meat or foods high in fat in a meta-analysis of 43 observational or interventional studies¹⁷⁵Bailie L, Loughrey MB, Coleman HG. Lifestyle risk factors for serrated colorectal polyps: a systematic review and meta-analysis. Gastroenterology. 2017 Jan;152(1):92-104.
• 9% lower risk of colorectal cancer over more than 11 years of follow up among men, but not women, eating less meat compared to “regular meat-eaters” in a very large observational study¹⁷⁶Watling CZ, Schmidt JA et al. Risk of cancer in regular and low meat-eaters, fish-eaters, and vegetarians: a prospective analysis of UK Biobank participants. BMC Medicine. 2022 Feb 24;20(1):73.

Trans-fat: modest evidence of higher cancer risk among people eating higher levels of foods with trans-fats

• Higher risk of colorectal cancer among people eating higher levels of trans-fatty acids (trans-fats) compared to lower levels in a meta-analysis of 9 observational studies¹⁷⁷Michels N, Specht IO, Heitmann BL, Chajès V, Huybrechts I. Dietary trans-fatty acid intake in relation to cancer risk: a systematic review and meta-analysis. Nutrition Reviews. 2021 Jun 4;79(7):758-776.

Sugar-sweetened beverages: modest evidence of substantially higher risk of early onset colorectal cancer among women drinking higher levels of sugar-sweetened beverages

• Double the risk of early onset colorectal cancer among women drinking 2 or more sugar-sweetened beverages a day compared to those drinking less than 1 a week in a large observational study¹⁷⁸Hur J, Otegbeye E et al. Sugar-sweetened beverage intake in adulthood and adolescence and risk of early-onset colorectal cancer among women. Gut. 2021 May 6:gutjnl-2020-323450.

Recommended eating pattern: strong evidence of lower risk of esophageal squamous cell carcinomas among people eating more fruit, vegetables, and white meat, but higher risk among those eating more red and processed meats or drinking maté

• Lower risk of esophageal squamous cell carcinomas among people eating more fruit, vegetables, and white meat compared to other people, but higher risk with more red and processed meats and maté drinking in a review of 100 meta-analysesa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies¹⁷⁹Castro C, Peleteiro B, Lunet N. Modifiable factors and esophageal cancer: a systematic review of published meta-analyses. Journal of Gastroenterology. 2018 Jan;53(1):37-51.

Fermented foods: strong evidence of lower risk of esophageal cancer among people eating fermented dairy foods

• Lower risk of cancer among people eating fermented dairy foods compared to other people in a subgroup analysis of a very large meta-analysis of 61 observational studies¹⁸⁰Zhang K, Dai H, Liang W, Zhang L, Deng Z. Fermented dairy foods intake and risk of cancer. International Journal of Cancer. 2019 May 1;144(9):2099-2108.

Fats: strong evidence of lower risk of digestive system cancers among people eating foods high in omega-3s

Good evidence of lower risk of digestive system cancer among people eating the highest levels of olive oil

• 17% lower risk of digestive system cancers among people eating foods high in omega-3s compared to others in a very large meta-analysis of 25 observational studies¹⁸¹Wang J, Zhang Y, Zhao L. Omega-3 PUFA intake and the risk of digestive system cancers: a meta-analysis of observational studies. Medicine (Baltimore). 2020 May;99(19):e20119.
• Lower risk of digestive system cancer among people eating the highest levels of olive oil compared to the lowest levels in a large meta-analysis of 19 observational studies¹⁸²Psaltopoulou T, Kosti RI, Haidopoulos D, Dimopoulos M, Panagiotakos DB. Olive oil intake is inversely related to cancer prevalence: a systematic review and a meta-analysis of 13,800 patients and 23,340 controls in 19 observational studies. Lipids in Health and Disease. 2011 Jul 30;10:127.

Meat: good evidence of higher risk of stomach cancer among people eating red or processed meat and lower risk with white meat

• Slightly to moderately higher risk of stomach among people eating either red or processed meats compared to other people, but lower risk among people eating white meat in meta-analyses of 42¹⁸³Zhao Z, Yin Z, Zhao Q. Red and processed meat consumption and gastric cancer risk: a systematic review and meta-analysis. Oncotarget. 2017 May 2;8(18):30563-30575. and 43¹⁸⁴Kim SR, Kim K et al. Effect of red, processed, and white meat consumption on the risk of gastric cancer: an overall and dose⁻response meta-analysis. Nutrients. 2019 Apr 11;11(4):826. observational studies

• Substantially (46-57%) lower risk of head and neck cancers among people eating higher amounts of carotenoids compared to other people in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies¹⁸⁵Leoncini E, Nedovic D et al. Carotenoid intake from natural sources and head and neck cancer: a systematic review and meta-analysis of epidemiological studies. Cancer Epidemiology, Biomarkers & Prevention. 2015 Jul;24(7):1003-11.
• 38% lower risk of head and neck cancer among people drinking tea in an umbrella review of meta-analyses and observational studies¹⁸⁶Kim TL, Jeong GH et al. Tea consumption and risk of cancer: an umbrella review and meta-analysis of observational studies. Advances in Nutrition. 2020 Nov 16;11(6):1437-1452. and about a 14% lower risk of nasopharyngeal cancer in meta-analyses of 6 observational studies¹⁸⁷Okekpa SI, S. M. N. Mydin RB, Ganeson S, Gopalan S, Musa MY. The association between tea consumption and nasopharyngeal cancer: a systematic review and meta-analysis. Asian Pacific Journal of Cancer Prevention. 2020 Aug 1;21(8):2183-2187.

• Higher risk of chronic lymphocytic leukemia among people eating a Western diet pattern compared to other people in a large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study¹⁸⁸Solans M, Castelló A et al. Adherence to the Western, Prudent, and Mediterranean dietary patterns and chronic lymphocytic leukemia in the MCC-Spain study. Haematologica. 2018 Nov;103(11):1881-1888.

• 44% lower risk of lung cancer among people who are heavy tobacco smokers and who drink at least 1 cup of tea compared to none in a large observational study¹⁸⁹Gnagnarella P, Maisonneuve P et al. Red meat, Mediterranean diet and lung cancer risk among heavy smokers in the COSMOS screening study. Annals of Oncology. 2013 Oct;24(10):2606-2611.
• Moderately lower risk of lung cancer among people eating higher levels of foods high in phytosterols, isoflavones, lignans, or phytoestrogens compared to other people in a mid-sized observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study¹⁹⁰Schabath MB, Hernandez LM, Wu X, Pillow PC, Spitz MR. Dietary phytoestrogens and lung cancer risk. JAMA. 2005 Sep 28;294(12):1493-504.
• 50% lower risk of lung cancer among women eating high levels of plant lignans and using hormone therapy compared to other people in a mid-sized observational study¹⁹¹Schabath MB, Hernandez LM, Wu X, Pillow PC, Spitz MR. Dietary phytoestrogens and lung cancer risk. JAMA. 2005 Sep 28;294(12):1493-504.
• 73% higher risk of lung cancer among people who are heavy tobacco smokers and who eat the most red meat compared to the least in a large observational study¹⁹²Gnagnarella P, Maisonneuve P et al. Red meat, Mediterranean diet and lung cancer risk among heavy smokers in the COSMOS screening study. Annals of Oncology. 2013 Oct;24(10):2606-2611.

Also see Flaxseed ›

Monounsaturated fat: good evidence of lower risk of basal cell carcinoma among people eating high levels of monounsaturated fat

• Slightly lower risk of basal cell carcinoma among people eating high levels of monounsaturated fat compared to other people, but no evidence of an effect from total fat and saturated fat in a very large meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 12 observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies¹⁹³Ruan L, Cheng SP, Zhu QX. Dietary fat intake and the risk of skin cancer: a systematic review and meta-analysis of observational studies. Nutrition and Cancer. 2020;72(3):398-408.

Polyunsaturated fat: good evidence of lower risk of squamous cell carcinoma (SCC) among people eating higher levels of omega-3s or with higher ratios of omega-3s to omega-6s compared to other people

Modest evidence of a slightly higher risk of SCC among people eating high levels of omega-6 polyunsaturated fats, with the risk partly dependent on the cooking methods used

• Lower risk of squamous cell carcinoma (SCC) among people eating higher levels of omega-3s or with higher ratios of omega-3s to omega-6s compared to other people in a very large meta-analysis of 12 observational studies¹⁹⁴Ruan L, Cheng SP, Zhu QX. Dietary fat intake and the risk of skin cancer: a systematic review and meta-analysis of observational studies. Nutrition and Cancer. 2020;72(3):398-408.
• Slightly higher risk of SCC among people eating high levels of omega-6 polyunsaturated fats, with the risk partly dependent on the cooking methods used, in a very large meta-analysis of 12 observational studies¹⁹⁵Ruan L, Cheng SP, Zhu QX. Dietary fat intake and the risk of skin cancer: a systematic review and meta-analysis of observational studies. Nutrition and Cancer. 2020;72(3):398-408.

Recommended diet pattern: good evidence of a moderately lower risk of ovarian cancer among women following a recommended dietary pattern for more than 4 years

• 40% lower risk of ovarian cancer among people eating lower amounts of dietary fat and higher amounts of vegetables, fruits, and grains for more than 4 years compared to other people in a very large RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects¹⁹⁶Prentice RL, Thomson CA et al. Low-fat dietary pattern and cancer incidence in the Women’s Health Initiative Dietary Modification Randomized Controlled Trial. Journal of the National Cancer Institute. 2007 Oct 17;99(20):1534-43.

Fiber: preliminary evidence of lower risk of ovarian cancer among American women of African descent eating more fiber from vegetables and fruits, but not from grains

• Lower risk of ovarian cancer among American women of African descent eating dietary fiber from vegetables and fruits compared to other people, but not with fiber from grains, in a large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study¹⁹⁷Qin B, Moorman PG et al. Dietary carbohydrate intake, glycaemic load, glycaemic index and ovarian cancer risk in African-American women. British Journal of Nutrition. 2016 Feb 28;115(4):694-702.

Fats: weak evidence of increased risk of epithelial ovarian cancer among people eating higher levels of trans-fats

• A weak trend toward a slightly higher risk of epithelial ovarian cancer among people eating higher levels of trans-fatty acids compared to lower levels in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 3 observational studies¹⁹⁸Hou R, Wu QJ, Gong TT, Jiang L. Dietary fat and fatty acid intake and epithelial ovarian cancer risk: evidence from epidemiological studies. Oncotarget. 2015 Dec 15;6(40):43099-119.

Recurrence

Meat and eggs: preliminary evidence of increased risk of prostate cancer recurrence among people eating eggs or poultry with skin, but no evidence of an effect with other types of meat

• Double the risk of recurrence among people with prostate cancer eating the highest amounts of eggs or poultry with skin compared to the lowest, but no evidence of an effect of eating processed and unprocessed red meat, fish, total poultry, and skinless poultry in a large observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study¹⁹⁹Richman EL, Stampfer MJ et al. Intakes of meat, fish, poultry, and eggs and risk of prostate cancer progression. American Journal of Clinical Nutrition. 2010 Mar;91(3):712-21.

Cancer risk

Modest evidence of lower risk of prostate cancer among people with higher serum concentrations of enterolactone, a metabolite of plant-based estrogens

Cruciferous vegetables, yellow-orange vegetables, or legumes: modest evidence of lower risk of prostate cancer among people eating more cruciferous vegetables, yellow-orange vegetables, or legumes

• Lower risk of aggressive prostate cancer, particularly extraprostatic disease, among men eating levels of vegetables, and especially more than 1 serving a week of cruciferous vegetables, compared to lower levels, although no evidence of an effect of vegetables or fruits on prostate cancer risk overall in a large observational study²⁰⁰Kirsh VA, Peters U et al; Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Prospective study of fruit and vegetable intake and risk of prostate cancer. Journal of the National Cancer Institute. 2007 Aug 1;99(15):1200-9.
• Lower risk of prostate cancer among men eating higher levels of yellow-orange and cruciferous vegetables compared to lower levels in a large observational study²⁰¹Kolonel LN, Hankin JH et al. Vegetables, fruits, legumes and prostate cancer: a multiethnic case-control study. Cancer Epidemiology, Biomarkers & Prevention. 2000 Aug;9(8):795-804.
• Lower risk of prostate cancer among men eating higher levels of legumes compared to lower levels in a large observational study²⁰²Kolonel LN, Hankin JH et al. Vegetables, fruits, legumes and prostate cancer: a multiethnic case-control study. Cancer Epidemiology, Biomarkers & Prevention. 2000 Aug;9(8):795-804.

Enterolactone, a metabolite of plant lignans: modest evidence of lower risk of prostate cancer among people with higher serum concentrations of enterolactone

• Lower risk of prostate cancer among people with higher serum concentration of enterolactone, although not related to eating lignans in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 11 observational studies,²⁰³He J, Wang S et al. Phytoestrogens and risk of prostate cancer: a meta-analysis of observational studies. World Journal of Surgical Oncology. 2015 Jul 31;13:231. with evidence that the benefit is greater for people with TT genotype of rs10993994 compared with CC and CT genotypes combined²⁰⁴Ho CK, Halley L, Wei J, Habib FK. Analysis of prostate cancer association with four single-nucleotide polymorphisms from genome-wide studies and serum phyto-estrogen concentrations. Prostate Cancer and Prostatic Diseases. 2012 Dec;15(4):365-8.
• Also see Flaxseed ›

Meat: good evidence of slightly higher risk of prostate cancer, but moderately higher risk of advanced prostate cancer, among people eating the highest levels of red or processed meats compared to the lowest

• Slightly higher risk of prostate cancer among people eating the highest levels of red or processed meats compared to the lowest—12% higher for red meat and 7% higher for processed meat—but more than 30% higher risk of advanced prostate cancer for each in a very large observational study²⁰⁵Sinha R, Park Y et al. Meat and meat-related compounds and risk of prostate cancer in a large prospective cohort study in the United States. American Journal of Epidemiology. 2009 Nov 1;170(9):1165-77.
• 20% lower risk of prostate cancer over more than 11 years of follow up among people eating fish only (no meat) and 31% lower risk among vegetarians compared to “regular meat-eaters” in a very large observational study²⁰⁶Watling CZ, Schmidt JA et al. Risk of cancer in regular and low meat-eaters, fish-eaters, and vegetarians: a prospective analysis of UK Biobank participants. BMC Medicine. 2022 Feb 24;20(1):73.

Fats: modest evidence of higher risk of prostate cancer among people eating higher levels of foods with trans-fats

• Higher risk of prostate cancer among people eating higher levels of trans-fatty acids (trans-fats) compared to lower levels in a meta-analysis of 11 observational studies²⁰⁷Michels N, Specht IO, Heitmann BL, Chajès V, Huybrechts I. Dietary trans-fatty acid intake in relation to cancer risk: a systematic review and meta-analysis. Nutrition Reviews. 2021 Jun 4;79(7):758-776.

• Slightly improved quality of life among people with cancer participating in an online physical activity and diet intervention compared to controls in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 24 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects²⁰⁸Furness K, Sarkies MN, Huggins CE, Croagh D, Haines TP. Impact of the method of delivering electronic health behavior change interventions in survivors of cancer on engagement, health behaviors, and health outcomes: systematic review and meta-analysis. Journal of Medical Internet Research. 2020 Jun 23;22(6):e16112.

Preliminary evidence of slightly better survival, lower risk of relapse, and better quality of life with a combination of diet and exercise

• Slightly better survival among people with ER positive breast cancer following either a healthier diet or regular exercise alone compared to other people, but almost 50% lower mortality within 10 years among those who adopted both diet and exercise compared to other people a large observational study²⁰⁹Pierce JP, Stefanick ML et al. Greater survival after breast cancer in physically active women with high vegetable-fruit intake regardless of obesity. Journal of Clinical Oncology. 2007 Jun 10;25(17):2345-51.
• 44% lower risk of relapse among women with breast cancer, either with or without obesity, who adopted a healthier diet and regular exercise in a large observational study²¹⁰Pierce JP, Stefanick ML et al. Greater survival after breast cancer in physically active women with high vegetable-fruit intake regardless of obesity. Journal of Clinical Oncology. 2007 Jun 10;25(17):2345-51.

• 30% lower colorectal cancer-specific mortality among people with the highest adherence to the 2007 World Cancer Research Fund/American Institute for Cancer Research lifestyle recommendations compared to the lowest adherence in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 38 observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods studies.²¹¹Solans M, Chan DSM, Mitrou P, Norat T, Romaguera D. A systematic review and meta-analysis of the 2007 WCRF/AICR score in relation to cancer-related health outcomes. Annals of Oncology. 2020 Mar;31(3):352-368.
• 42% lower mortality at 5 years among people with colorectal cancer who followed the American Cancer Society’s Nutrition and Physical Activity Guidelines for Cancer Survivors most closely compared to those who followed them least in a mid-sized observational study²¹²Van Blarigan EL, Fuchs CS et al. Association of survival with adherence to the American Cancer Society Nutrition and Physical Activity Guidelines for Cancer Survivors after colon cancer diagnosis: The CALGB 89803/Alliance Trial. JAMA Oncology. 2018 Apr 12.

• Substantially improved physical function among people with head and neck cancer undergoing radiotherapy treatment participating in an intervention of nutrition and in some cases exercise compared to controls in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 13 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects²¹³Bye A, Sandmael JA et al. Exercise and nutrition interventions in patients with head and neck cancer during curative treatment: a systematic review and meta-analysis. Nutrients. 2020 Oct 22;12(11):3233.

Preliminary evidence of decreasing prostate-specific antigen (PSA) levels among men with prostate cancer with a lifestyle intervention including a health-promoting diet, physical activity, group support, and stress management

• Decreasing PSA levels among men with early stage prostate cancer in a “watchful waiting” program combining a low-fat, vegetarian diet with physical activity, group support and stress management, compared to rising PSA levels in the group receiving usual care in a small RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects²¹⁴Ornish D, Weidner G et al. Intensive lifestyle changes may affect the progression of prostate cancer. Journal of Urology. 2005 Sep;174(3):1065-9; discussion 1069-70.

No evidence of an effect on anxiety among people participating in diet intervention alone in a combined analysis of studies, but modest evidence of slightly less anxiety with a combined intervention of diet and physical activity

• No significant improvement in anxiety with dietary interventions in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 16 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects²¹⁵Firth J, Marx W et al. The effects of dietary improvement on symptoms of depression and anxiety: a meta-analysis of randomized controlled trials. Psychosomatic Medicine. 2019 Apr;81(3):265-280
• Little impact on anxiety and/or depression among people with symptoms with dietary interventions (an effect in 8 of 17 controlled trialsa study design in which people are assigned to either an experimental group or a control group to compare the outcomes from different treatment; assignment is not random, and so this is not as strong a study design as a randomized controlled trial, but still stronger than an uncontrolled trial) in a systematic review²¹⁶Opie RS, O’Neil A, Itsiopoulos C, Jacka FN. The impact of whole-of-diet interventions on depression and anxiety: a systematic review of randomised controlled trials. Public Health Nutrition. 2015 Aug;18(11):2074-93.
• Slightly less anxiety among people with cancer participating in an online, combined intervention of diet and physical activity in a meta-analysis of 24 RCTs²¹⁷Furness K, Sarkies MN, Huggins CE, Croagh D, Haines TP. Impact of the method of delivering electronic health behavior change interventions in survivors of cancer on engagement, health behaviors, and health outcomes: systematic review and meta-analysis. Journal of Medical Internet Research. 2020 Jun 23;22(6):e16112.

Modest evidence of less depression and anxiety among women with overweight or obesity participating in an intervention of physical activity and/or diet

• Fewer symptoms of depression and anxiety among women with overweight or obesity with a lifestyle intervention of physical activity and/or diet in a meta-analysis of 5 RCTs²¹⁸van Dammen L, Wekker V et al. A systematic review and meta-analysis of lifestyle interventions in women of reproductive age with overweight or obesity: the effects on symptoms of depression and anxiety. Obesity Reviews. 2018 Dec;19(12):1679-1687.

Preliminary evidence of less fatigue, anxiety, and depression, and better quality of life among women with early breast cancer participating in an intervention of both diet and exercise

• Less fatigue, anxiety, and depression, and better quality of life among women with early breast cancer participating in an intervention of both diet and exercise compared to controls in a mid-sized RCT²¹⁹Carayol M, Ninot G et al. Short- and long-term impact of adapted physical activity and diet counseling during adjuvant breast cancer therapy: the “APAD1” randomized controlled trial. BMC Cancer. 2019 Jul 25;19(1):737.

Weak evidence of of better markers of insulin growth factor among men participating in a diet and exercise program

• Better markers of insulin growth factor among men with a diet and exercise program compared to baseline in a small observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study²²⁰Ngo TH, Barnard RJ, Tymchuk CN, Cohen P, Aronson WJ. Effect of diet and exercise on serum insulin, IGF-I, and IGFBP-1 levels and growth of LNCaP cells in vitro (United States). Cancer Causes & Control. 2002;13(10):929–935.
• Better markers of insulin growth factor and less serum-stimulated LNCaP cell growth among men participating in a diet and exercise program compared to baseline in a small observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study²²¹Ngo TH, Barnard RJ, Tymchuk CN, Cohen P, Aronson WJ. Effect of diet and exercise on serum insulin, IGF-I, and IGFBP-1 levels and growth of LNCaP cells in vitro (United States). Cancer Causes & Control. 2002;13(10):929–935.

Weak evidence of lower markers of glycemic imbalance among men with prostate cancer participating in a diet and an exercise program

• No change in insulin resistance and metabolic syndrome related to androgen deprivation therapy (ADT), but weak trends toward lower markers of glycemic imbalance among men with prostate cancer and without diabetes treated who were treated with metformin, a low glycemic indexan indication of the ability of a food to raise blood sugar, in a value from zero (not at all) to 100 (pure glucose); high-GI foods are digested quickly and release glucose rapidly into the bloodstream, while low-GI foods release glucose slowly and steadily into the bloodstream diet and an exercise program compared to controls receiving only ADT in a small RCT²²²Nobes JP, Langley SE, Klopper T, Russell-Jones D, Laing RW. A prospective, randomized pilot study evaluating the effects of metformin and lifestyle intervention on patients with prostate cancer receiving androgen deprivation therapy. BJU International. 2012 May;109(10):1495-502.

• Both reduced caloric intake alone and exercise alone were linked to better levels of breast cancer-related sex hormones among healthy, physically inactive postmenopausal women, with the broadest benefits from combining both diet and exercise compared to controls in a meta-analysisa statistical analysis that combines the results of two or more research studies; the results of smaller research studies addressing the same or similar questions can be analyzed as though they are one bigger, more powerful study of 6 RCTsrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects²²³de Roon M, May AM et al. Effect of exercise and/or reduced calorie dietary interventions on breast cancer-related endogenous sex hormones in healthy postmenopausal women. Breast Cancer Research. 2018 Aug 2;20(1):81.
• Better levels of serum leptin among people with breast cancer, and also with overweight or obesity, with counseling on caloric restriction and aerobic exercise compared to basic nutritional counseling and upper-body progressive resistance training in a small RCT²²⁴Demark-Wahnefried W, Rogers LQ et al. Randomized trial of weight loss in primary breast cancer: impact on body composition, circulating biomarkers and tumor characteristics. International Journal of Cancer. 2020 May 15;146(10):2784-2796.

• Higher risk of consuming ‘unhealthy’ foods when experiencing stress in observational studies²²⁵Zellner DA, Loaiza S et al. Food selection changes under stress. Physiology & Behavior. 2006 Apr 15;87(4):789-93; Yau YH, Potenza MN. Stress and eating behaviors. Minerva Endocrinology. 2013 Sep;38(3):255-67.

Integrative physicians Keith Block, MD, and Janet Spitzer, MD, inform us about foods, food components, and eating behaviors that promote a stress response:²²⁶Block KI. Life over Cancer: The Block Center Program for Integrative Cancer Care. New York: Bantam Dell. 2009; Spitzer J. Personal communication with Laura Pole. April 16, 2018.

• Low-carb, high-fat diet
• Low-carb, high-protein diet
• High ratio of omega-6 to omega-3 fatty acids ›
• Foods containing caffeine
• Timing of snacks and drinks
  • Eating within one hour of bedtime
  • Eating a heavy evening meal or snack
• Overeating