How can oral vitamin C help you? What the research says

Vitamin C, available in several foods and dietary supplements, shows some anticancer effects, including better survival among people with breast cancer.

How can oral vitamin C help you? What the research says

We summarize the clinical evidence for each medical benefit here. We begin with our assessment of the strength of evidence within each category, followed by a brief summary of individual studies or reviews of several studies. In assessing the strength of evidence, we consider the study design, number of participants, and the size of the treatment effect (how much outcomes changed with treatment).

To see more details, click the plus sign to the right of any section.

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)

Learn more about how we research and rate therapies and practices in How We Rate Therapies ›

Improving treatment outcomes

Is oral vitamin C linked to improved survival? Is it linked to less cancer growth or metastasis? Does it enhance the anticancer action of other treatments or therapies? We present the evidence.

Advanced cancer

Insufficient (conflicting) evidencepreclinical 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) (this is the CancerChoices definition; other researchers and studies may define this differently) of an effect on survival among people with advanced cancer treated with vitamin C supplements

Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of a link between shorter survival, low vitamin C levels, and advanced cancer

Vitamin C supplements: Insufficient (conflicting) evidence of an effect on survival among people with advanced cancer treated with vitamin C supplements

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 survival among people with advanced cancer treated with 10 g oral vitamin C per day 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 effects¹Creagan ET, Moertel CG et al. Failure of high-dose vitamin C (ascorbic acid) therapy to benefit patients with advanced cancer. A controlled trial. New England Journal of Medicine. 1979; 301(13):687-90.
No evidence of an effect on disease progression or survival among people with advanced colorectal cancer with no history of chemotherapy treated with 10 g oral vitamin C daily compared to placebo in a small RCT²Moertel CG, Fleming TR et al. High-dose vitamin C versus placebo in the treatment of patients with advanced cancer who have had no prior chemotherapy. A randomized double-blind comparison. New England Journal of Medicine. 1985;312(3):137-41.
Longer survival times after the date of untreatability among people with advanced cancer treated with 10 g supplemental ascorbate per day compared to controls receiving usual care in a mid-sized RCT³Cameron E, Pauling L. Supplemental ascorbate in the supportive treatment of cancer: prolongation of survival times in terminal human cancer. Proceedings of the National Academy of Sciences of the USA. 1976;73(10):3685-9; Cameron E, Pauling L. Supplemental ascorbate in the supportive treatment of cancer: reevaluation of prolongation of survival times in terminal human cancer. Proceedings of the National Academy of Sciences of the USA. 1978;75(9):4538-42.
Apparently longer survival (not analyzed for significance) among people with terminal cancer treated with large doses of ascorbate compared to lower doses in a small controlled triala 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 trial⁴Murata A, Morishige F, Yamaguchi H. Prolongation of survival times of terminal cancer patients by administration of large doses of ascorbate. International Journal for Vitamin and Nutrition Research Suppl. 1982;23:103-13.

Vitamin C levels: preliminary evidence of a link between shorter survival, low vitamin C levels, and advanced cancer; we don’t know if advanced cancer contributes to low vitamin C levels, or if low vitamin C levels contribute to advanced cancer and shorter survival, or if the links work in several directions

A shorter survival and low vitamin C levels among people with advanced cancer 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 study⁵Mayland CR, Bennett MI, Allan K. Vitamin C deficiency in cancer patients. Palliative Medicine. 2005 Jan;19(1):17-20.

Brain cancer

Preliminary evidence of better survival among people with grade 4 malignant glioma with higher intake of vitamin C in their diet

Breast cancer

Modest evidencesignificant 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 observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) of better survival among women with breast cancer taking vitamin C supplements

Better overall survival among people with breast cancer taking vitamin C supplements after cancer diagnosis compared to no supplements 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 8 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 studies⁷Li Y, Lin Q, Lu X, Li W. Post-diagnosis use of antioxidant vitamin supplements and breast cancer prognosis: a systematic review and meta-analysis. Clinical Breast Cancer. 2021;21(6):477-485.
Lower overall mortality among people with breast cancer taking vitamin C supplements compared to no supplements in a meta-analysis of 4 observational studies⁸Kanellopoulou A, Riza E, Samoli E, Benetou V. Dietary supplement use after cancer diagnosis in relation to total mortality, cancer mortality and recurrence: a systematic review and meta-analysis. Nutrition and Cancer. 2021;73(1):16-30.
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 survival during 5 years of follow up among women with early breast cancer treated with 3g ascorbic acid per day 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 effects;⁹Poulter JM, White WF, Dickerson JW. Ascorbic acid supplementation and five year survival rates in women with early breast cancer. Acta Vitaminological et Enzymologica. 1984;6(3):175-82. our note: even though this is an RCT, it included only 27 women with cancer—a number probably too small to determine if treatment with vitamin C had much effect on survival

Leukemia

Preliminary evidence of better response to treatment with DNA methyltransferase inhibitors (DNMTis) among people with myeloid cancers treated with oral vitamin C

Vitamin C combined with other therapies

Modest evidence of slightly lower mortality among people taking vitamin C or other antioxidant supplements (vitamin E or multivitamin) after a breast cancer diagnosis

No evidence of an effect on response rates or survival after chemotherapy among people with advanced non-small cell lung cancer treated with high-dose vitamins C, E and beta carotene in a small study

Weak evidenceone 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 (this is the CancerChoices definition; other researchers and studies may define this differently) of tumor response among people with multiple myeloma treated with bortezomib, oral ascorbic acid and melphalan

Preliminary evidence of better overall survival among people with acute myeloid leukemia and NPM1 mutations but no evidence of an effect among people with wild-type NPM1 treated with supplemental vitamin C and vitamin D

Preliminary evidence of lower markers of tumor proliferation among people with prostate cancer treated with vitamin K3 and vitamin C

Preliminary evidence of resolution of lesions among people with basal cell carcinoma treated with a topical solution of ascorbic acid and dimethyl sulfoxide

Weak evidence of normalization of CA-125 levels after cytoreduction surgery among 2 women with advanced epithelial ovarian cancer treated with oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10, and a multivitamin/mineral complex, plus intravenous vitamin C in addition to chemotherapy

Vitamin C supplements with other antioxidants

Modest evidence of slightly lower mortality among people taking vitamin C or other antioxidant supplements (vitamin E or multivitamin) after a breast cancer diagnosis

No evidence of an effect on response rates or survival after chemotherapy among people with advanced non-small cell lung cancer treated with high-dose vitamins C, E, and beta carotene in a small study

Slightly lower mortality among people taking vitamin C or other antioxidant supplements (vitamin E or multivitamin) after a breast cancer diagnosis compared to no vitamin C or antioxidants 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 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 studies¹²Poole EM, Shu X et al. Postdiagnosis supplement use and breast cancer prognosis in the After Breast Cancer Pooling Project. Breast Cancer Research and Treatment. 2013 Jun;139(2):529-37.
No evidence of an effect on response rates or survival after chemotherapy (paclitaxel and carboplatin) among people with advanced non-small cell lung cancer treated with high-dose vitamins C, E, and beta carotene compared to chemotherapy alone 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 effects¹³Pathak AK, Bhutani M et al. Chemotherapy alone vs. chemotherapy plus high dose multiple antioxidants in patients with advanced non small cell lung cancer. Journal of the American College of Nutrition. 2005;24(1):16-21.

Vitamin C and vitamin D: preliminary evidence of better overall survival among people with acute myeloid leukemia and NPM1 mutations but no evidence of an effect among people with wild-type NPM1 treated with supplemental vitamin C and vitamin D

Better overall survival among people with acute myeloid leukemia and NPM1 mutations but no evidence of an effect among people with wild-type NPM1, and no evidence of any effect on response rate, or relapse incidence among those treated with supplemental vitamin C and vitamin D from day 10 of chemotherapy until hematologic recovery from induction and consolidation compared to no supplementation in a mid-sized observational study¹⁴Mouchel PL, Bérard E et al. Vitamin C and D supplementation in acute myeloid leukemia. Blood Advances. 2023 Sep 6:bloodadvances.2023010559.

Oral vitamin C with chemotherapy: weak evidence of tumor response among people with multiple myeloma treated with bortezomib, oral ascorbic acid, and melphalan

Disease control in 94% of participants, with time to progression of disease of 19 months and median progression-free survivalthe time during and after treatment of a disease that a patient lives without disease progression (worsening) of 13 months among people with newly diagnosed multiple myeloma treated with bortezomib, oral ascorbic acid, and melphalan 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 design¹⁵Berenson JR, Yellin O et al. Bortezomib, ascorbic acid and melphalan (BAM) therapy for patients with newly diagnosed multiple myeloma: an effective and well-tolerated frontline regimen. European Journal of Haematology. 2009;82(6):433-439.

Vitamin C supplements and vitamin K3 (menadione): preliminary evidence of lower markers of tumor proliferation among people with prostate cancer treated with vitamin K3 and vitamin C

Lower markers of tumor proliferation (homocysteine and prostate specific antigen (PSA) levels) after 6 weeks among people with prostate cancer treated with 50 mg/m2 menadione (vitamin K3) and 50 mg/m2 vitamin C per day for 7 days treatment 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 small RCT¹⁶Lasalvia-Prisco E, Cucchi S et al. Serum markers variation consistent with autoschizis induced by ascorbic acid-menadione in patients with prostate cancer. Medical Oncology. 2003;20(1):45-52.

Topical vitamin C with dimethyl sulfoxide (DMSO): preliminary evidence of resolution of lesions among people with basal cell carcinoma treated with a topical solution of ascorbic acid and dimethyl sulfoxide

Higher rate of complete resolution of lesions among people with basal cell carcinoma treated with a topical solution of 30% ascorbic acid in 95% dimethyl sulfoxide twice daily for 8 weeks compared to topical imiquimod in a small RCT¹⁷Burke B, Bailie JE. Randomized trial of topical ascorbic acid in DMSO versus imiquimod for the treatment of basal cell carcinoma. Biomedicine & Pharmacotherapy. 2022;148:112710.

Oral vitamin C combined with intravenous vitamin C, other antioxidants, and chemotherapy: weak evidence of normalization of CA-125 levels after cytoreduction surgery among 2 women with advanced epithelial ovarian cancer treated with oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10, and a multivitamin/mineral complex, plus intravenous vitamin C in addition to chemotherapy

Normalization of CA-125 levels after cytoreduction surgery among 2 women with advanced epithelial ovarian cancer treated with oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10, and a multivitamin/mineral complex, plus intravenous vitamin C in addition to chemotherapy in case studies¹⁸Drisko JA, Chapman J, Hunter VJ. The use of antioxidants with first-line chemotherapy in two cases of ovarian cancer. Journal of the American College of Nutrition. 2003 Apr;22(2):118-23.

Optimizing your body terrain

Does oral vitamin C promote an environment within your body that is less supportive of cancer development, growth, or spread? We present the evidence.

See Optimizing Your Body Terrain ›

Find medical professionals who specialize in managing body terrain factors: Finding Integrative Oncologists and Other Practitioners ›

High blood sugar and insulin resistance

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 blood sugar and insulin among people with type 2 diabetes treated with vitamin C overall, although weak evidenceone 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 (this is the CancerChoices definition; other researchers and studies may define this differently) of a possible effect at a dose of 1000 mg vitamin C per day

Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of a link between plasma vitamin C concentrations and type 2 diabetes or prediabetes

Vitamin C supplements

No evidence of an effect on blood sugar and insulin among people with type 2 diabetes treated with vitamin C overall, although weak evidence of a possible effect at a dose of 1000 mg vitamin C per day

Lower markers of blood sugar (fasting blood sugar or HbA1c) but no evidence of an effect on insulin resistancea condition in which cells in your muscles, fat, and liver don’t respond well to insulin and can’t efficiently take up glucose from your blood for energy (insulin or HOMA-IR) among people with type 2 diabetes treated with vitamin C 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 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 a subset of 178 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 effects¹⁹Kazemi A, Ryul Shim S et al. Comparison of nutritional supplements for glycemic control in type 2 diabetes: a systematic review and network meta-analysis of randomized trials. Diabetes Research and Clinical Practice. 2022;191:110037.
Lower marker of blood sugar (HbA1c) among adults with type 2 diabetes treated with vitamin C supplements compared to no supplements in a meta-analysis of a subset of 178 RCTs²⁰Kazemi A, Ryul Shim S et al. Comparison of nutritional supplements for glycemic control in type 2 diabetes: a systematic review and network meta-analysis of randomized trials. Diabetes Research and Clinical Practice. 2022;191:110037.
No evidence of an effect on insulin resistance (HOMA) among people with type 2 diabetes mellitus treated with vitamin C supplements compared to no supplementation in a meta-analysis of 14 RCTs²¹Khodaeian M, Tabatabaei-Malazy O et al. Effect of vitamins C and E on insulin resistance in diabetes: a meta-analysis study. European Journal of Clinical Investigation. 2015;45(11):1161-1174.
A smaller change of fasting blood glucose, but no evidence of an effect on HbA1c, fasting insulin, and HOMA-IR among people with type 2 diabetes treated with vitamin C for 8 weeks, whether with or without rutin, compared to controls receiving antidiabetic treatment only in a small RCT²²Ragheb SR, El Wakeel LM, Nasr MS, Sabri NA. Impact of rutin and vitamin C combination on oxidative stress and glycemic control in patients with type 2 diabetes. Clinical Nutrition ESPEN. 2020;35:128-135.
Lower fasting blood sugar, HbA1c, and serum insulin among people with type 2 diabetes treated with 1000 mg vitamin C per day for 6 weeks, although no effect from 500 mg vitamin C, 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 design²³Afkhami-Ardekani M, Shojaoddiny-Ardekani A. Effect of vitamin C on blood glucose, serum lipids & serum insulin in type 2 diabetes patients. Indian Journal of Medical Research. 2007;126(5):471-474.

Vitamin C levels

Preliminary evidence of a link between plasma vitamin C concentrations and type 2 diabetes or prediabetes; we do not know whether low vitamin C levels contribute to diabetes, or if diabetes contributes to low vitamin C levels, or if the link works in both directions

Lower plasma vitamin C concentrations among people with type 2 diabetes or prediabetes compared to people with normal glucose tolerance 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 study²⁴Wilson R, Willis J et al. Inadequate vitamin C status in prediabetes and type 2 diabetes mellitus: associations with glycaemic control, obesity, and smoking. Nutrients. 2017;9(9):997.

Immune function

Increased immune system activation is not always beneficial, so your oncology team needs to determine whether immune activation would be favorable in your situation.

Preliminary evidence of a higher marker of immune activity among acutely hospitalized patients treated with oral vitamin C

Preliminary evidence of lower levels of some markers of immune activity during multimodal treatment for esophageal adenocarcinoma among people treated with oral vitamin C

Weak evidenceone 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 (this is the CancerChoices definition; other researchers and studies may define this differently) of downregulation of immune activity (activated NF-κB and cytokines) among people with Barrett’s esophagus and specialized intestinal metaplasia treated with 1000 mg oral vitamin C

Preliminary evidence of less DNA damage in peripheral blood lymphocytes among employees working at a thermal power plant treated with oral vitamin C (not specific to cancer)

Preliminary evidence of a link between neutrophil counts, febrile neutropenia, and low vitamin C levels during and after conditioning chemotherapy and hematopoietic stem cell transplantation among people with hematological cancer

Vitamin C supplements

Preliminary evidence of a higher level of a marker of immune activity among acutely hospitalized patients treated with oral vitamin C

A higher level of a marker of immune activity (mononuclear leukocytes) among acutely hospitalized patients treated with 500 mg oral vitamin C twice a day compared to no vitamin C 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 effects²⁵Zhang M, Robitaille L, Eintracht S, Hoffer LJ. Vitamin C provision improves mood in acutely hospitalized patients. Nutrition. 2011 May;27(5):530-3.

Preliminary evidence of lower levels of some markers of immune activity during multimodal treatment for esophageal adenocarcinoma among people treated with oral vitamin C

Lower levels of cytokines—modulators of inflammation and carcinogenesis― 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. on NF-κB activity during multimodal treatment for esophageal adenocarcinoma among people treated with 1000 mg oral vitamin C per day for 4 weeks compared to no supplementation in a small RCT²⁶Abdel-Latif MMM, Babar M, Kelleher D, Reynolds JV. A pilot study of the impact of vitamin C supplementation with neoadjuvant chemoradiation on regulators of inflammation and carcinogenesis in esophageal cancer patients. Journal of Cancer Research and Therapeutics. 2019 Jan-Mar;15(1):185-191.

Weak evidence of downregulation of immune activity (activated NF-κB and cytokines) among people with Barrett’s esophagus and specialized intestinal metaplasia treated with 1000 mg oral vitamin C

Downregulation of activated NF-κB and cytokines among 35% of people with Barrett’s esophagus and specialized intestinal metaplasia treated with 1000 mg oral vitamin C per day for 4 weeks 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 design²⁷Babar M, Abdel-Latif MM et al. Pilot translational study of dietary vitamin C supplementation in Barrett’s esophagus. Diseases of the Esophagus. 2010 Apr;23(3):271-6.

Preliminary evidence of less DNA damage in peripheral blood lymphocytes among employees working at a thermal power plant treated with oral vitamin C (not specific to cancer)

Less DNA damage in peripheral blood lymphocytes among employees working at a thermal power plant treated with 1000 mg oral vitamin C per day for 3 months compared to no intervention in a small RCT²⁸Bagheri Hosseinabadi M, Khanjani N et al. The effect of vitamin E and C on comet assay indices and apoptosis in power plant workers: a double blind randomized controlled clinical trial. Mutation Research. Genetic Toxicology and Environmental Mutagenesis. 2020;850-851:503150.

Vitamin C levels

The lowest mean neutrophil counts, corresponding with febrile neutropenia during and after conditioning chemotherapy and hematopoietic stem cell transplantation among people with hematological cancer with the lowest vitamin C levels compared to higher levels 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 study²⁹Carr AC, Spencer E et al. Patients undergoing myeloablative chemotherapy and hematopoietic stem cell transplantation exhibit depleted vitamin C status in association with febrile neutropenia. Nutrients. 2020;12(6):1879.

Inflammation

Good evidencesignificant effects in one large or several mid-sized and well-designed clinical studies (randomized controlled trials (RCTs) with an appropriate placebo or other strong comparison control or observational studies that control for confounds) (this is the CancerChoices definition; other researchers and studies may define this differently) of lower levels of markers of inflammation among people treated with vitamin C

Preliminary evidence of a link between vitamin C levels and inflammation; the link likely works in both directions

Vitamin C supplements

Good evidence of lower levels of markers of inflammation among people treated with oral vitamin C

A lower level of an inflammatory marker (IL-6) after a single exercise session, 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. on creatine kinase, CRP, and cortisol levels among healthy volunteers treated with vitamin C supplements compared to placebo 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 18 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 effects³⁰Righi NC, Schuch FB et al. Effects of vitamin C on oxidative stress, inflammation, muscle soreness, and strength following acute exercise: meta-analyses of randomized clinical trials. European Journal of Nutrition. 2020;59(7):2827-2839.
A lower marker of inflammation (CRP) among adults, some of whom had chronic diseases, treated with supplemental vitamin C compared to no supplementation in a review of 4 systematic reviews³¹Corrao S, Mallaci Bocchio R et al. Does evidence exist to blunt inflammatory response by nutraceutical supplementation during COVID-19 pandemic? An overview of systematic reviews of vitamin D, vitamin C, melatonin, and zinc. Nutrients. 2021;13(4):1261.
Weak trendsan 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 balancing inflammation (lower IL-6 and higher IL-10 mRNA) after 6 weeks of exercising among elderly women treated with 1000 mg vitamin C per day for 6 weeks 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 small RCT³²Żychowska M, Grzybkowska A et al. Effect of six weeks 1000 mg/day vitamin C supplementation and healthy training in elderly women on genes expression associated with the immune response—a randomized controlled trial. Journal of the International Society of Sports Nutrition. 2021;18(1):19.

Vitamin C levels

Preliminary evidence of a link between vitamin C levels and inflammation

The highest markers of inflammation (CRP) during and after conditioning chemotherapy and hematopoietic stem cell transplantation among people with hematological cancer with the lowest vitamin C levels compared to higher levels 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 study³³Carr AC, Spencer E et al. Patients undergoing myeloablative chemotherapy and hematopoietic stem cell transplantation exhibit depleted vitamin C status in association with febrile neutropenia. Nutrients. 2020;12(6):1879.
A link between inflammation (high CRP levels) and low vitamin C levels among people with advanced cancer in a small observational study³⁴Mayland CR, Bennett MI, Allan K. Vitamin C deficiency in cancer patients. Palliative Medicine. 2005 Jan;19(1):17-20.

Oxidative stress

Preliminary evidence of normalized levels of antioxidant enzymes during tamoxifen treatment among postmenopausal women with breast cancer treated with oral vitamin C

Preliminary evidence of lower oxidative stressan imbalance between free radicals and antioxidants in your body in which antioxidant levels are lower than normal; this imbalance can cause harmful oxidation reactions in your body chemistry after radionuclide therapy (RNT) among people with prostate cancer or neuroendocrine tumors treated with oral vitamin C before RNT

Vitamin C of unspecified dose and route

Preliminary evidence of normalized levels of antioxidant enzymes during tamoxifen treatment among postmenopausal women with breast cancer treated with oral vitamin C

Normalized levels of antioxidant enzymes during tamoxifen treatment among postmenopausal women with breast cancer treated with vitamin C after either 45 days or 90 days of tamoxifen compared to controls not treated with vitamin C 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 effects³⁵Muralikrishnan G, Amanullah S et al. Effect of vitamin C on lipidperoxidation and antioxidant status in tamoxifen-treated breast cancer patients. Chemotherapy. 2010;56(4):298-302.

Vitamin C supplements

Preliminary evidence of lower oxidative stress after radionuclide therapy (RNT) among people with prostate cancer or neuroendocrine tumors treated with oral vitamin C before RNT

No rise in a marker of oxidative stress (malondialdehyde) and glutathione after radionuclide therapy (RNT) among people with prostate cancer or neuroendocrine tumors treated with 500 mg effervescent vitamin C tablets for 2 days before RNT compared to elevated markers in controls in a small RCT;³⁶Jafari E, Ahmadzadehfar H, Bagheri D, Amini A, Assadi M. Assessment of early oxidative stress following the use of radiotheranostics agents 177Lu-PSMA for prostate cancer and 177Lu-DOTATATE for neuroendocrine tumors; radioprotective effect of vitamin C. Nuclear Medicine Communications. 2021;42(3):325-331. most of the time, lower levels of oxidative stress are considered a good terrain situation. However, because the anticancer effects of radiotherapy and some chemotherapies are due to oxidation, your oncologist may not want vitamin C’s antioxidant effects interfering with radiation or chemotherapy. Be sure your oncologist knows if you are taking vitamin C supplements or other antioxidants before starting radiotherapy or chemotherapy. See Safety and precautions ›

Good evidence of less oxidative stress (lipid peroxidation) after exercise among healthy volunteers treated with vitamin C supplements

Less oxidative stress (lipid peroxidation) after a single exercise session among healthy volunteers treated with vitamin C supplements 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 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 18 RCTs³⁷Righi NC, Schuch FB et al. Effects of vitamin C on oxidative stress, inflammation, muscle soreness, and strength following acute exercise: meta-analyses of randomized clinical trials. European Journal of Nutrition. 2020;59(7):2827-2839.

Preliminary evidence of lower DNA damage in peripheral blood lymphocytes among employees working at a thermal power plant treated with oral vitamin C

Lower markers of oxidative stress (malondialdehyde and F2-IsoPs) after performing cycling exercise at 33% of peak oxygen consumption for 20 minutes among people with type 2 diabetes mellitus treated with 1000 mg vitamin C for 6 weeks compared to placebo in a small RCT³⁸Boonthongkaew C, Tong-Un T et al. Vitamin C supplementation improves blood pressure and oxidative stress after acute exercise in patients with poorly controlled type 2 diabetes mellitus: a randomized, placebo-controlled, cross-over study. Chinese Journal of Physiology. 2021;64(1):16-23.

No evidence of an effect on oxidative stress among people with type 2 diabetes treated with vitamin C for 8 weeks, whether with or without rutin, compared to controls receiving antidiabetic treatment only in a small RCT³⁹Ragheb SR, El Wakeel LM, Nasr MS, Sabri NA. Impact of rutin and vitamin C combination on oxidative stress and glycemic control in patients with type 2 diabetes. Clinical Nutrition ESPEN. 2020;35:128-135.

Vitamin C levels

Preliminary evidence of higher lipid oxidation during and after conditioning chemotherapy and hematopoietic stem cell transplantation among people with hematological cancer with lower vitamin C levels

Higher lipid oxidation during and after conditioning chemotherapy and hematopoietic stem cell transplantation among people with hematological cancer with lower vitamin C levels compared to higher levels 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 study⁴⁰Carr AC, Spencer E et al. Patients undergoing myeloablative chemotherapy and hematopoietic stem cell transplantation exhibit depleted vitamin C status in association with febrile neutropenia. Nutrients. 2020;12(6):1879.

Your microbiome

Preliminary evidence of better markers of microbiomethe collection of microbes living on and within your body health (higher microbial alpha diversity and fecal short-chain fatty acids) among healthy volunteers treated with oral vitamin C

Other terrain factors

Preliminary evidence of higher plasma vitamin C levels and upregulation of several viral defense genes in malignant myeloid cells but not T cells during treatment with DNA methyltransferase inhibitors among people with myeloid cancers treated with oral vitamin C

Vitamin C combined with other therapies

Preliminary evidence of lower markers of oxidative stress among people treated with oral vitamin C, vitamin E, and sometimes with selenium

Weak evidence of less inflammation among people with cancer-related anorexiaabnormal loss of appetite, often leading to weight loss/cachexiaweakness and wasting of the body due to severe chronic illness and oxidative stress treated with a special diet, antioxidants, medroxyprogesterone acetate, and celecoxib

Oral vitamin C and other antioxidants: preliminary evidence of lower markers of oxidative stress among people treated with oral vitamin C, vitamin E, and sometimes selenium

Lower markers of oxidative stress (malondialdehyde and reactive oxygen species) among women with endometriosis treated with 1000 mg vitamin C and 800 IU vitamin E per day for 8 weeks 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 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 effects⁴³Amini L, Chekini R et al. The effect of combined vitamin C and vitamin E supplementation on oxidative stress markers in women with endometriosis: a randomized, triple-blind placebo-controlled clinical trial. Pain Research and Management. 2021;2021:5529741.
Less DNA damage in peripheral blood lymphocytes among employees working at a thermal power plant treated with 1000 mg oral vitamin C and 400 IU oral vitamin E per day for 3 months compared to no intervention in a small RCT⁴⁴Bagheri Hosseinabadi M, Khanjani N et al. The effect of vitamin E and C on comet assay indices and apoptosis in power plant workers: a double blind randomized controlled clinical trial. Mutation Research. Genetic Toxicology and Environmental Mutagenesis. 2020;850-851:503150.
Lower markers of oxidative stress after thyroidectomy and 3.7 GBq 131I after levothyroxine withdrawal among people with thyroid cancer treated with 2000 mg vitamin C, 1000 mg vitamin E, and 400 µg selenium for 21 days before 131I compared to no treatment in a small controlled triala 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 trial⁴⁵Rosário PW, Batista KC, Calsolari MR. Radioiodine-induced oxidative stress in patients with differentiated thyroid carcinoma and effect of supplementation with vitamins C and E and selenium (antioxidants). Archives of Endocrinology and Metabolism. 2016;60(4):328-332.

Vitamin C supplements with a special diet and pharmaceuticals: weak evidence of less inflammation among people with cancer-related anorexia/cachexia and oxidative stress treated with a special diet, antioxidants, medroxyprogesterone acetate, and celecoxib

Fewer proinflammatory cytokines (IL-6) and TNF-𝛼 among people with cancer-related anorexia/cachexia and oxidative stress treated with a diet rich in polyphenols, antioxidants (alpha-lipoic acid, carbocysteine lysine salt, vitamin E, A and C), and pharmaconutritional support enriched with omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid), medroxyprogesterone acetate, and celecoxib for 4 months 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 design⁴⁶Mantovani G, Macciò A et al. A phase II study with antioxidants, both in the diet and supplemented, pharmaconutritional support, progestagen, and anti-cyclooxygenase-2 showing efficacy and safety in patients with cancer-related anorexia/cachexia and oxidative stress. Cancer Epidemiology, Biomarkers & Prevention. 2006;15(5):1030-1034.

Managing side effects and promoting wellness

Is oral vitamin C linked to fewer or less severe side effects or symptoms? Is it linked to less toxicity from cancer treatment? Does it support your quality of life or promote general well-being? We present the evidence.

Side effects as a whole

Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of less toxicity and fewer cancer therapy delays after 6 months among children with acute lymphoblastic leukemia with higher vitamin C in their diets

Body composition and cachexia

Preliminary evidence of higher body weight during chemotherapy among people with acute myeloid leukemia treated with vitamin C supplements

Changes in appetite

Oral symptoms

Weak (conflicting) evidenceone 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 (this is the CancerChoices definition; other researchers and studies may define this differently) of better salivary flow after radiotherapy among people with head and neck cancer treated with chewable ascorbic acid tablets

Good evidencesignificant effects in one large or several mid-sized and well-designed clinical studies (randomized controlled trials (RCTs) with an appropriate placebo or other strong comparison control or observational studies that control for confounds) (this is the CancerChoices definition; other researchers and studies may define this differently) of fewer symptoms of mucosal irritation induced by Lugol chromoendoscopy among people with esophageal dysplasia and carcinoma treated with a vitamin C solution spray

Vitamin C supplements

Weak (conflicting) evidence of better salivary flow after radiotherapy among people with head and neck cancer treated with chewable ascorbic acid tablets

Lower reduction in salivary flow after radiotherapy among people with head and neck cancer treated with chewable ascorbic acid tablets compared to chewing gum 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 effects⁵¹Dutta S, Mukhopadhyay S, Biswas S, Das A, Banerjee S. Chewable vitamin C in the management of radiation-induced xerostomia: Is it the end of the dark tunnel? Supportive Care in Cancer 2021 29:SUPPL 1 (S153).
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 measures of salivary gland function a month after 131I treatment among people with differentiated thyroid carcinoma treated with 100 mg oral vitamin C every 2 hours for a total of 600–800 mg daily for 3 days, starting 2 hours after 131I treatment, 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 design⁵²Cheng Y, Tong H et al. Effect of vitamin E and supragingival scaling on salivary gland function in patients with differentiated thyroid cancer treated with 131I. Nuclear Medicine Communications. 2022;43(9):995-1003.
No evidence of a difference on salivary absorbed dose, a marker of protective effect on the salivary glands, after therapeutic radioiodine among people with thyroid cancer treated with 100 mg oral vitamin D lozenges at 1, 5, 13, or 25 hours after radiotherapy and continuing every 4 hours in the daytime over 6 days in a small comparison trial⁵³Liu B, Kuang A et al. Influence of vitamin C on salivary absorbed dose of 131I in thyroid cancer patients: a prospective, randomized, single-blind, controlled trial. Journal of Nuclear Medicine. 2010 Apr;51(4):618-23.
Higher secretion function of parotid glands after a large dose of 131I among people with differentiated thyroid carcinoma (DTC) treated with 100 mg vitamin C tablets per 2 hours for a total of 600–800 mg per day for 3 days before radiotherapy compared to baseline in a small uncontrolled trial⁵⁴Tong H, Luo L et al. Effects of vitamin C and selenium on salivary glands in patients with DTC treated with 131I. Journal of Nuclear Medicine. 2020;61(12):1445.

Vitamin C solution

Good evidence of fewer symptoms of mucosal irritation induced by Lugol chromoendoscopyvisualization of the esophagus using a fiber-optic scope and dyeing the esophageal tissue with iodine solution among people with esophageal dysplasia and carcinoma treated with a vitamin C solution spray

Fewer symptoms of mucosal irritation caused by different concentrations of Lugol iodine solution during Lugol chromoendoscopy among people with superficial esophageal squamous cell carcinoma treated with vitamin C solution compared to sprayed distilled water, and similar to sodium thiosulfate solution, in a large RCT⁵⁵Nie X, Ding J et al. Effectiveness of vitamin C solution in reducing adverse reactions caused by painless lugol chromoendoscopy: a multicenter randomized controlled trial. Journal of Clinical Gastroenterology. 2022;56(8):688-696.
Fewer mucosal irritation symptoms induced by Lugol chromoendoscopy among people with esophageal dysplasia and carcinoma treated with a 2% vitamin C solution spray compared to saline spray in a mid-sized RCT⁵⁶Jin D, Wang J et al. The safety and efficacy of 2% vitamin C solution spray for relief of mucosal irritation caused by Lugol chromoendoscopy: a multicenter, randomized, double-blind, parallel trial. Gastrointestinal Endoscopy. 2020;92(3):554-564.

Pain

No evidence of an effect on pain among people with advanced cancer treated with 10 g oral vitamin C in a mid-sized study

Quality of life and physical function

No evidence of an effect on strength among people with advanced cancer treated with 10 g oral vitamin C in a mid-sized study

Preliminary evidence of better quality of life scores during radiotherapy among people with head and neck cancer treated with chewable ascorbic acid tablets

Oral vitamin C combined with other therapies

Weak evidence of better scores for quality of life and function (physical, cognitive, emotional, and role function), less appetite loss, nausea and vomiting, pain, and fatigue among people with terminal cancer treated with both intravenous and oral vitamin C

Preliminary evidence of lower rates of fungal infection, hemorrhage, or macrophage activation syndrome among people with acute myeloid leukemia treated with supplemental vitamin C and vitamin D

Weak evidence of better appetite, body weight and lean body mass, less fatigue, and better quality of life among people with cancer-related anorexia/cachexia and oxidative stressan imbalance between free radicals and antioxidants in your body in which antioxidant levels are lower than normal; this imbalance can cause harmful oxidation reactions in your body chemistry treated with a diet rich in polyphenols, antioxidants, medroxyprogesterone acetate, and celecoxib

No evidence of an effect on fatigue while participating in 10 weeks of strength training among people with breast cancer treated with vitamins C and E

Weak evidence of less dry mouth (xerostomia) 6 months after radiotherapy among people with head and neck cancer treated with vitamins C and E

Weak evidence of higher iron levels among people with advanced cancer and low iron levels treated with micronised microencapsulated ferric pyrophosphate and ascorbic acid

Weak evidence of better fatigue scores during treatment with sunitinib among people with kidney cancer treated with vitamin C, isoquercetin, and nicotinic acid

Both intravenous and oral vitamin C: weak evidence of better scores for quality of life and function (physical, cognitive, emotional, and role function), less appetite loss, nausea and vomiting, pain, and fatigue among people with terminal cancer treated with both intravenous and oral vitamin C

Better scores for quality of life and function (physical, cognitive, emotional, and role function), less appetite loss, nausea and vomiting, pain, and fatigue among people with terminal cancer treated with 10 g intravenous vitamin C twice 3 days apart and 4 g oral vitamin C daily for a week 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 design⁶⁰Yeom CH, Jung GC, Song KJ. Changes of terminal cancer patients’ health-related quality of life after high dose vitamin C administration. Journal of Korean Medical Science. 2007;22(1):7-11.

Vitamin C and vitamin D supplements: preliminary evidence of lower rates of fungal infection, hemorrhage, or macrophage activation syndrome among people with acute myeloid leukemia treated with supplemental vitamin C and vitamin D

Lower rates of fungal infection, hemorrhage, or macrophage activation syndrome among those treated with supplemental vitamin C and vitamin D from day 10 of chemotherapy until hematologic recovery from induction and consolidation compared to no supplementation 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 study⁶¹Mouchel PL, Bérard E et al. Vitamin C and D supplementation in acute myeloid leukemia. Blood Advances. 2023 Sep 6:bloodadvances.2023010559.

Vitamin C supplements with a special diet and pharmaceuticals: weak evidence of better appetite, body weight and lean body mass, less fatigue, and better quality of life among people with cancer-related anorexia/cachexia and oxidative stress treated with a diet rich in polyphenols, antioxidants, medroxyprogesterone acetate, and celecoxib

Better appetite, body weight and lean body mass, less fatigue, and better quality of life among people with cancer-related anorexia/cachexia and oxidative stress treated with a diet rich in polyphenols, antioxidants (alpha-lipoic acid, carbocysteine lysine salt, vitamin E, A and C), and pharmaconutritional support enriched with omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid), medroxyprogesterone acetate, and celecoxib for 4 months compared to baseline in a small uncontrolled trial⁶²Mantovani G, Macciò A et al. A phase II study with antioxidants, both in the diet and supplemented, pharmaconutritional support, progestagen, and anti-cyclooxygenase-2 showing efficacy and safety in patients with cancer-related anorexia/cachexia and oxidative stress. Cancer Epidemiology, Biomarkers & Prevention. 2006;15(5):1030-1034.

Vitamin C supplements with vitamin E

No evidence of an effect on fatigue while participating in 10 weeks of strength training among people with breast cancer treated with vitamins C and E

No evidence of an effect on general fatigue, physical fatigue, or fatigability while participating in 10 weeks of strength training among people with breast cancer treated with 500 mg vitamin C and 180 mg vitamin E per day 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 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 effects⁶³de Lima FD, Battaglini CL et al. Effect of strength training and antioxidant supplementation on perceived and performance fatigability in breast cancer survivors: a randomized, double-blinded, placebo-controlled study. Applied Physiology, Nutrition, and Metabolism. 2020;45(10):1165-1173.

Weak evidence of better markers of cardiovascular risk factors during tamoxifen treatment among postmenopausal people with breast cancer treated with oral vitamin C and vitamin E

Better markers of cardiovascular risk factors (lower total cholesterol, free cholesterol, very low density lipoprotein cholesterol, and triglycerides, and higher high density lipoprotein cholesterol and ester cholesterol) during tamoxifen treatment among postmenopausal people with breast cancer treated with 500 mg oral vitamin C and 400 mg vitamin E for 90 days compared to baseline in a small uncontrolled trial⁶⁴Babu JR, Sundravel S et al. Salubrious effect of vitamin C and vitamin E on tamoxifen-treated women in breast cancer with reference to plasma lipid and lipoprotein levels. Cancer Letters. 2000 Apr 3;151(1):1-5.

Weak evidence of less dry mouth (xerostomia) 6 months after radiotherapy among people with head and neck cancer treated with vitamins C and E

Less dry mouth (xerostomia) 6 months after radiotherapy among people with head and neck cancer treated with 100 IU vitamin E and 500 mg vitamin C twice per day during radiotherapy compared to 1 month after radiotherapy, but no improvement among people receiving placebo, in a small RCT⁶⁵Chung MK, Kim do H et al. Randomized trial of vitamin C/E Complex for prevention of radiation-induced xerostomia in patients with head and neck cancer. Otolaryngology—Head and Neck Surgery. 2016;155(3):423-430.

Vitamin C with micronised microencapsulated ferric pyrophosphate: weak evidence of higher iron levels among people with advanced cancer and low iron levels treated with micronised microencapsulated ferric pyrophosphate and ascorbic acid

Higher iron levels (sideremia, ferritinemia, and hemoglobin) among people with advanced cancer and low iron levels treated with 30 mg micronised microencapsulated ferric pyrophosphate and 80 mg ascorbic acid for 30 days in a small uncontrolled trial⁶⁶Pappalardo A, Currenti W et al. Effects of micronised microencapsulated ferric pyrophosphate supplementation in patients with advanced cancer and iron deficiency: a single-centre cohort pilot study. Blood Transfusion. 2019 May;17(3):196-199.

Vitamin C, isoquercetin, and nicotinic acid: weak evidence of better fatigue scores during treatment with sunitinib among people with kidney cancer treated with vitamin C, isoquercetin, and nicotinic acid

Better fatigue scores during treatment with sunitinib among people with kidney cancer treated with isoquercetin, vitamin C (ascorbic acid), and nicotinic acid twice a day for 81 days compared to baseline in a small uncontrolled trial⁶⁷Buonerba C, De Placido P et al. Isoquercetin as an adjunct therapy in patients with kidney cancer receiving first-line sunitinib (quasar): results of a phase I trial. Frontiers in Pharmacology. 2018 Mar 16;9:189.

Symptoms not specific to cancer

Modest evidencesignificant 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 observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) of less anxiety related to stress among people treated with oral vitamin C (not specific to cancer)

Preliminary evidence of less change in body composition during exercising among elderly women treated with oral vitamin C (not specific to cancer)

Modest evidence of higher fat-free mass among middle-aged and older people with higher dietary intakes or plasma levels of vitamin C (not specific to cancer)

Modest evidence of lower fracture risk among men, but not women, with the highest plasma vitamin C concentrations (not specific to cancer)

Modest evidence of lower blood pressure related to stress or exercise among people treated with oral vitamin C (not specific to cancer)

Modest evidence of less depression among people treated with oral vitamin C (not specific to cancer)

Preliminary evidence of lower measures of pain and less nausea and vomiting after surgery among adults treated with oral vitamin C 1 hour before surgery (not specific to cancer)

No evidence of an effect on muscle soreness or muscle strength after a single exercise session among healthy volunteers treated with vitamin C supplements in a combined analysis of studies

Preliminary evidence of a higher rate of penile-vaginal intercourse among healthy young adults treated with oral vitamin C

Modest evidence of lower risk of pulmonary morbidity or organ failure and shorter duration of mechanical ventilation and length of stay in intensive care after surgery among critically ill people treated with vitamin E (alpha-tocopherol) and ascorbate (not specific to cancer)

Preliminary evidence of less diabetic peripheral neuropathydamage to the peripheral nerves outside the brain and spinal cord among people treated with DiVFuSS formulation

Anxiety: modest evidence of less anxiety related to stress among people treated with oral vitamin C (not specific to cancer)

Less anxiety related to stress among women treated with high-dose, sustained-release oral vitamin C compared to controls in a systematic review of 14 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 trial⁶⁸McCabe D, Lisy K, Lockwood C, Colbeck M. The impact of essential fatty acid, B vitamins, vitamin C, magnesium and zinc supplementation on stress levels in women: a systematic review. JBI Database of Systematic Reviews and Implementation Reports. 2017;15(2):402–453.
Lower anxiety among the 25% of people with more anxiety, but no evidence of an effect overall among graduate students treated with 1000 mg oral ascorbic acid 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 effects⁶⁹Moritz B, Schwarzbold ML et al. Effects of ascorbic acid on anxiety state and affect in a non-clinical sample. Acta Neurobiologiae Experimentalis. 2017;77(4):362-372.
Lower anxiety levels among high school students treated with 500 mg vitamin C per day compared to placebo in a small RCT⁷⁰de Oliveira IJ, de Souza VV, Motta V, Da-Silva SL. Effects of oral vitamin C supplementation on anxiety in students: a double-blind, randomized, placebo-controlled trial. Pakistan Journal of Biological Sciences. 2015 Jan;18(1):11-8.
Lower anxiety scores among people with type 2 diabetes treated with 1000 mg vitamin C per day for 6 weeks compared to placebo or vitamin E in a small RCT⁷¹Mazloom Z, Ekramzadeh M, Hejazi N. Efficacy of supplementary vitamins C and E on anxiety, depression and stress in type 2 diabetic patients: a randomized, single-blind, placebo-controlled trial. Pakistan Journal of Biological Sciences. 2013 Nov 15;16(22):1597-600.

Body composition

Preliminary evidence of less change in body composition during exercising among elderly women treated with oral vitamin C (not specific to cancer)

Modest evidence of higher fat-free mass among middle-aged and older people with higher dietary intakes or plasma levels of vitamin C (not specific to cancer)

Less change in body composition during 6 weeks of exercising among elderly women treated with 1000 mg vitamin C per day for 6 weeks compared to placebo in a small RCT⁷²Żychowska M, Grzybkowska A et al. Effect of six weeks 1000 mg/day vitamin C supplementation and healthy training in elderly women on genes expression associated with the immune response—a randomized controlled trial. Journal of the International Society of Sports Nutrition. 2021;18(1):19.
Higher fat-free mass among middle-aged and older people with higher dietary intakes of vitamin C compared to lower intake, or with sufficient plasma levels (50 μmol/L or higher) compared to insufficient plasma levels in a 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 study⁷³Lewis LN, Hayhoe RPG et al. Lower dietary and circulating vitamin C in middle- and older-aged men and women are associated with lower estimated skeletal muscle mass. Journal of Nutrition. 2020 Oct 12;150(10):2789-2798.

Bone symptoms: modest evidence of lower fracture risk among men, but not women, with the highest plasma vitamin C concentrations (not specific to cancer)

Lower fracture risk among men, but not women, with the highest plasma vitamin C concentrations compared to the lowest, but no evidence of an effect of vitamin C intake, in a very large observational study⁷⁴Finck H, Hart AR et al. Cross-sectional and prospective associations between dietary and plasma vitamin C, heel bone ultrasound, and fracture risk in men and women in the European Prospective Investigation into Cancer in Norfolk cohort. American Journal of Clinical Nutrition. 2015 Dec;102(6):1416-24.

Cardiovascular symptoms: modest evidence of lower blood pressure related to stress or exercise among people treated with oral vitamin C

Lower blood pressure related to stress among women treated with high-dose, sustained-release vitamin C compared to controls in a systematic review of 14 controlled trials⁷⁵McCabe D, Lisy K, Lockwood C, Colbeck M. The impact of essential fatty acid, B vitamins, vitamin C, magnesium and zinc supplementation on stress levels in women: a systematic review. JBI Database of Systematic Reviews and Implementation Reports. 2017;15(2):402–453.
Lower blood pressure and higher plasma nitric oxide—important in blood pressure and vascular function—after performing cycling exercise at 33% of peak oxygen consumption for 20 minutes among people with type 2 diabetes mellitus treated with 1000 mg vitamin C for 6 weeks compared to placebo in a small RCT⁷⁶Boonthongkaew C, Tong-Un T et al. Vitamin C supplementation improves blood pressure and oxidative stress after acute exercise in patients with poorly controlled type 2 diabetes mellitus: a randomized, placebo-controlled, cross-over study. Chinese Journal of Physiology. 2021;64(1):16-23.

Depression or mood symptoms: modest evidence of less depression among people treated with oral vitamin C

71% less mood disturbance and 51% less psychological distress among acutely hospitalized people treated with 500 mg vitamin C twice a day compared to 5000 IU vitamin D per day in a mid-sized RCT⁷⁷Wang Y, Liu XJ et al. Effects of vitamin C and vitamin D administration on mood and distress in acutely hospitalized patients. American Journal of Clinical Nutrition. 2013 Sep;98(3):705-11.
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 the efficacy of citalopram among adults with major depressive disorder treated with vitamin C compared to placebo in a small RCT⁷⁸Sahraian A, Ghanizadeh A, Kazemeini F. Vitamin C as an adjuvant for treating major depressive disorder and suicidal behavior, a randomized placebo-controlled clinical trial. Trials. 2015 Mar 14;16:94.
Lower depression scores among people with depression treated with antidepressants and also treated with ascorbic acid tablets for 8 weeks compared to placebo in a small RCT⁷⁹Aburawi SM, Ghambirlou FA, Attumi AA, Altubuly RA, Kara AA. Effect of ascorbic acid on mental depression drug therapy: clinical study. Journal of Psychology & Psychotherapy. 2014;4(1).
No evidence of an effect on stress and depression scores among people with type 2 diabetes treated with 1000 mg oral vitamin C per day for 6 weeks compared to placebo or vitamin E in a small RCT⁸⁰Mazloom Z, Ekramzadeh M, Hejazi N. Efficacy of supplementary vitamins C and E on anxiety, depression and stress in type 2 diabetic patients: a randomized, single-blind, placebo-controlled trial. Pakistan Journal of Biological Sciences. 2013 Nov 15;16(22):1597-600.
Fewer depressive symptoms among children with major depressive disorder treated with fluoxetine and also treated with 1000 mg oral vitamin C per day compared to placebo in a small RCT⁸¹Amr M, El-Mogy A, Shams T, Vieira K, Lakhan SE. Efficacy of vitamin C as an adjunct to fluoxetine therapy in pediatric major depressive disorder: a randomized, double-blind, placebo-controlled pilot study. Nutrition Journal. 2013 Mar 9;12:31.
34% less mood disturbance among acutely hospitalized patients treated with 500 mg oral vitamin C twice a day compared to 1000 IU vitamin D twice a day in a small RCT⁸²Zhang M, Robitaille L, Eintracht S, Hoffer LJ. Vitamin C provision improves mood in acutely hospitalized patients. Nutrition. 2011 May;27(5):530-3.
Lower depression scores among healthy young adults treated with 3000 mg oral ascorbic acid per day (Cetebe) compared to placebo in a small RCT⁸³Brody S. High-dose ascorbic acid increases intercourse frequency and improves mood: a randomized controlled clinical trial. Biological Psychiatry. 2002 Aug 15;52(4):371-4.

Pain: preliminary evidence of lower measures of pain and less nausea and vomiting after surgery among adults treated with oral vitamin C 1 hour before surgery (not specific to cancer)

Lower measure of pain (mean pain scores, total morphine consumption, supplemental analgesic), and less nausea and vomiting for 24 hours after surgery among adults treated with oral vitamin C 1 hour before surgery compared to placebo in a mid-sized RCT⁸⁴Laflı Tunay D, Türkeün Ilgınel M et al. Comparison of the effects of preoperative melatonin or vitamin C administration on postoperative analgesia. Bosnian Journal of Basic Medical Sciences. 2020;20(1):117-124.

Physical function and muscle soreness: no evidence of an effect on muscle soreness or muscle strength after a single exercise session among healthy volunteers treated with vitamin C supplements in a combined analysis of studies

No evidence of an effect on muscle soreness or muscle strength after a single exercise session among healthy volunteers treated with vitamin C supplements compared to placebo 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 18 RCTs⁸⁵Righi NC, Schuch FB et al. Effects of vitamin C on oxidative stress, inflammation, muscle soreness, and strength following acute exercise: meta-analyses of randomized clinical trials. European Journal of Nutrition. 2020;59(7):2827-2839.

Sexual difficulties: preliminary evidence of a higher rate of penile-vaginal intercourse among healthy young adults treated with oral vitamin C

A higher rate of penile-vaginal intercourse, most prominent among women and people not cohabiting with their sexual partner, among healthy young adults treated with 3000 mg oral ascorbic acid per day (Cetebe) compared to placebo in a small RCT⁸⁶Brody S. High-dose ascorbic acid increases intercourse frequency and improves mood: a randomized controlled clinical trial. Biological Psychiatry. 2002 Aug 15;52(4):371-4.

Vitamin C combined with other therapies

Vitamin C and vitamin E: modest evidence of lower risk of pulmonary morbidity or organ failure and shorter duration of mechanical ventilation and length of stay in intensive care after surgery among critically ill people treated with vitamin E (alpha-tocopherol) and ascorbate

Lower risk of pulmonary morbidity or organ failure and shorter duration of mechanical ventilation and length of stay in intensive care after surgery among critically ill people treated with vitamin E (alpha-tocopherol) and ascorbate compared to controls receiving standard care in a mid-sized RCT⁸⁷Nathens AB, Neff MJ et al. Randomized, prospective trial of antioxidant supplementation in critically ill surgical patients. Annals of Surgery. 2002;236(6):814-822.

DiVFuSS formulation of vitamins C, D3, and E (d-α tocopherol), zinc oxide, eicosapentaenoic acid, docosahexaenoic acid, α-lipoic acid (racemic mixture), coenzyme Q10, mixed tocotrienols/tocopherols, zeaxanthin, lutein, benfotiamine, N-acetyl cysteine, grape seed extract, resveratrol, turmeric root extract, green tea leaf, and Pycnogenol: preliminary evidence of less diabetic peripheral neuropathy among people treated with DiVFuSS formulation

Less diabetic peripheral neuropathy among people treated with DiVFuSS formulation for 6 months compared to placebo in a small RCT⁸⁸Chous AP, Richer SP, Gerson JD, Kowluru RA. The Diabetes Visual Function Supplement Study (DiVFuSS). British Journal of Ophthalmology. 2016 Feb;100(2):227-34.

Commentary

Vitamin C’s role in cancer-related anemia

CancerChoices Senior Clinical Consultant Laura Pole, RN, MSN, OCNS: People with cancer may become anemic for several reasons. One is iron deficiency, the most common nutritional deficiency in advanced cancer patients and the cause of iron-deficiency anemia.⁸⁹Pappalardo A, Currenti W et al. Effects of micronised microencapsulated ferric pyrophosphate supplementation in patients with advanced cancer and iron deficiency: a single-centre cohort pilot study. Blood Transfusion. 2019 May;17(3):196-199. Diagnosing this kind of anemia involves blood tests, including complete blood count (CBC) and ferritin levels.⁹⁰Iron deficiency anemia—diagnosis and treatment. Mayo Clinic. January 4, 2022. Viewed June 6, 2023.

Vitamin C deficiency may also be a common and underrecognized cause of anemia. One study concluded that vitamin C deficiency was linked to anemia, regardless of iron status, as well as inflammation as shown by higher levels of ferritin.⁹¹Sehbai A, Asif N. De novo anemia and relationship with vitamin C deficiency and zinc deficiency in a southern Delaware population, a retrospective analysis. Blood. 2015;126(23):4547.

Because vitamin C is capable of turning iron in your blood into a more soluble and therefore more usable form and can also improve iron absorption, vitamin C deficiency may also play a role in iron-deficiency anemia. Because of these effects, for years doctors routinely recommended people take vitamin C along with iron supplements. However, one well-designed research found that the effects of iron supplements on hemoglobin levels and iron stores are no different whether vitamin C is taken with iron or not.⁹²Li N, Zhao G et al. The efficacy and safety of vitamin C for iron supplementation in adult patients with iron deficiency anemia: a randomized clinical trial. JAMA Network Open. 2020 Nov 2;3(11):e2023644. Unfortunately, this study did not report the effects of adding vitamin C among the study participants who may have been deficient in vitamin C. We know from studies of other therapies—such as vitamin D—that people with a deficiency may get a benefit from taking supplements, but other people may not. People with vitamin C deficiency who need iron supplementation may benefit from taking vitamin C. This study didn’t investigate this.

A side note related to iron supplementation: Ferrous sulfate (the standard type of iron prescribed) is poorly absorbed and typically constipating. Ferrous gylcinate or bisglycinate (sometimes called “gentle iron” or “iron chelate”) is far better absorbed and does not cause bowel changes. For this reason, if iron is needed, ferrous glycinate is a preferable form.

Because evidence on whether or not to supplement with vitamin C to manage anemia is inconclusive, we provide some key take-aways based on the best available information:⁹³Li N, Zhao G et al. The efficacy and safety of vitamin C for iron supplementation in adult patients with iron deficiency anemia: a randomized clinical trial. JAMA Network Open. 2020 Nov 2;3(11):e2023644; Simonson W. Should vitamin C routinely be given with oral iron supplements? Geriatric Nursing. 2019 May-Jun;40(3):327-328.

Iron is usually well-absorbed, and iron-deficiency anemia typically responds quickly to iron supplements. Before adding another supplement such as vitamin C, check that you are taking the iron supplement correctly for optimal absorption: take it at the right time, not with foods that compete with iron absorption, and avoid interactions with any drugs or other supplements that decrease absorption. Favor ferrous gylcinate or bisglycinate for iron supplementation, as these are absorbed better and are less constipating than ferrous sulfate.
Check for and correct a vitamin C deficiency. Ask your doctor or registered dietitian whether increasing vitamin C in your diet would be sufficient to bring your levels to an appropriate range or if they recommend supplementation. Talk to your doctor before starting any supplements.
If you supplement with vitamin C when taking iron, the dose recommended is 200 mg or more of vitamin C for every 30 mg of iron. This dose of vitamin C, especially when combined with iron, may increase your risk of nausea and diarrhea.
Some products combining iron and vitamin C tend to be more expensive than separate supplements and may not have an adequate dose of vitamin C to provide benefit.

Addition from CancerChoices advisor Jen Green, ND, FABNO: Vitamin C deficiency is so common in cancer patients that I would recommend using 500 mg vitamin C orally to treat deficiencies regardless of iron status. “Extensive literature demonstrates that cancer patients experience vitamin C deficiency correlated with reduced oral intake, inflammation, infection, disease processes, and treatments such as radiation, chemotherapy, and surgery.”⁹⁴Klimant E, Wright H, Rubin D, Seely D, Markman M. Intravenous vitamin C in the supportive care of cancer patients: a review and rational approach. Current Oncology. 2018 Apr;25(2):139-148.

Reducing cancer risk

Is oral vitamin C linked to lower risks of developing cancer or of recurrence? We present the evidence.

Cancer as a whole

Modest evidencesignificant 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 observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) of a link between low vitamin C levels and risk of cancer as a whole

Vitamin C supplements

No evidence of an effect on risk of cancer as a whole among people treated with oral vitamin C in large controlled studies

No evidence of an effect on risk of cancer as a whole or cancer mortality among women without cancer at baseline treated with 500 mg oral vitamin C daily for an average of more than 9 years 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 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 effects⁹⁵Lin J, Cook NR et al. Vitamins C and E and beta carotene supplementation and cancer risk: a randomized controlled trial. Journal of the National Cancer Institute. 2009;101(1):14-23.
No evidence of an effect on risk of cancer as a whole during 14 years of follow-up among healthy men aged 50 or older treated with 500 mg oral vitamin C daily for 10 years compared to placebo in a very large RCT⁹⁶Wang L, Sesso HD et al. Vitamin E and C supplementation and risk of cancer in men: posttrial follow-up in the Physicians’ Health Study II randomized trial. American Journal of Clinical Nutrition. 2014;100(3):915-923.

Vitamin C levels

Modest evidence of a link between low vitamin C levels and risk of cancer as a whole; we don’t know if low vitamin C levels contribute to cancer risk, or if having cancer leads to low vitamin C levels, or if the link works in both directions

Lower cancer mortality among Chinese people without cancer at baseline with higher circulating vitamin C levels compared to lower levels in a mid-size 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 study⁹⁷Wang SM, Fan JH et al. Association of plasma vitamin C concentration to total and cause-specific mortality: a 16-year prospective study in China. Journal of Epidemiology and Community Health. 2018 Dec;72(12):1076-1082.
Lower risk of distal colon cancer among people with higher dietary vitamin C intake compared to lower intake in a mid-sized observational study⁹⁸Leenders M, Leufkens AM et al. Plasma and dietary carotenoids and vitamins A, C and E and risk of colon and rectal cancer in the European Prospective Investigation into Cancer and Nutrition. International Journal of Cancer. 2014 Dec 15;135(12):2930-9.
Lower levels of vitamin C among people with newly diagnosed cancer compared to controls in a mid-sized observational study⁹⁹Torun M, Yardim S et al. Serum beta-carotene, vitamin E, vitamin C and malondialdehyde levels in several types of cancer. Journal of Clinical Pharmacy and Therapeutics. 1995 Oct;20(5):259-63.
Lower levels of vitamin C among people with cancer compared to healthy controls in a small observational study¹⁰⁰Mahdavi R, Faramarzi E, Seyedrezazadeh E, Mohammad-Zadeh M, Pourmoghaddam M. Evaluation of oxidative stress, antioxidant status and serum vitamin C levels in cancer patients. Biological Trace Element Research. 2009 Jul;130(1):1-6.

Bladder cancer

No evidence of an effect on risk of urothelial cell carcinoma among people with higher plasma vitamin C levels in a large study

Breast cancer

Modest evidence of lower risk of recurrence among people with breast cancer taking vitamin C supplements

No evidence of an effect on breast cancer risk among people with higher levels of vitamin C intake from diet and/or supplements in a combined analysis of studies

Vitamin C supplements

Modest evidence of lower risk of recurrence among people with breast cancer taking vitamin C supplements; also see weak evidenceone 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 (this is the CancerChoices definition; other researchers and studies may define this differently) of higher risk of recurrence and death among people with breast cancer taking antioxidants as a whole in Safety and precautions ›

Lower risk of recurrence among people with breast cancer taking vitamin C supplements compared to no supplements 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 studies¹⁰²Kanellopoulou A, Riza E, Samoli E, Benetou V. Dietary supplement use after cancer diagnosis in relation to total mortality, cancer mortality and recurrence: a systematic review and meta-analysis. Nutrition and Cancer. 2021;73(1):16-30.

No evidence of an effect on breast cancer risk among people with higher levels of vitamin C intake from diet and/or supplements in a combined analysis of studies

No evidence of an effect on breast cancer risk among people with higher levels of vitamin C intake from diet and/or supplements compared to lower levels in a very large meta-analyses of 19 observational studies and one 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 effects¹⁰³Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

Vitamin C levels

Preliminary evidence of a link between low vitamin C levels and breast cancer risk; we don’t know if low vitamin C levels contribute to cancer risk, or if having cancer leads to low vitamin C levels, or if the link works in both directions

Lower serum ascorbate levels, with decreasing serum levels with increasing stage of the disease, among people with breast cancer compared to healthy controls in a mid-sized observational study¹⁰⁴Ramaswamy G, Krishnamoorthy L. Serum carotene, vitamin A, and vitamin C levels in breast cancer and cancer of the uterine cervix. Nutrition and Cancer. 1996;25(2):173-7.

Colorectal cancer

Insufficient evidencepreclinical 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) (this is the CancerChoices definition; other researchers and studies may define this differently) of lower colorectal cancer risk among people with higher levels of vitamin C intake from diet or both diet and supplements, but not supplements alone

Weak evidenceone 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 (this is the CancerChoices definition; other researchers and studies may define this differently) of lower risk of colon cancer among people with higher levels of vitamin C intake from diet or supplements, but not both diet and supplements

No evidence of an effect on rectal cancer risk among people with higher levels of vitamin C intake from diet

Preliminary evidence of lower risk of colon cancer among people with higher diet-derived circulating levels of vitamin C

Preliminary (conflicting) evidence of an effect on risk of colorectal cancer among people with genetically predicted higher levels of circulating vitamin C levels

Vitamin C intake

Insufficient evidence of lower colorectal cancer risk among people with higher levels of vitamin C intake from diet or both diet and supplements, but not supplements alone

No evidence of an effect on risk of colorectal cancer among people taking vitamin C, either alone or with other antioxidant supplements, 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 very large 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 14 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 effects¹⁰⁵Bjelakovic G, Nikolova D, Simonetti RG, Gluud C. Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis. Lancet. 2004;364(9441):1219-1228.
Weak trendsan 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 lower risk of colorectal cancer among people with higher levels of vitamin C intake from diet (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 studies) or both diet and supplements (1 observational study), but not supplements alone (2 observational studies and 2 RCTs), compared to lower levels in very large meta-analyses of observational studies¹⁰⁶Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

Weak evidence of lower risk of colon cancer among people with higher levels of vitamin C intake from diet or supplements, but not both diet and supplements

Weak trends toward lower colon cancer risk among people with higher levels of vitamin C intake from diet (5 studies) or supplements (3 studies), but not both diet and supplements (2 studies), compared to lower levels in very large meta-analyses of observational studies¹⁰⁷Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

No evidence of an effect on rectal cancer risk among people with higher levels of vitamin C intake from diet; also see evidence of higher risk of rectal cancer among people with higher vitamin C supplement intake in Safety and precautions ›

No evidence of an effect on rectal cancer risk among people with higher levels of vitamin C intake from diet compared to lower levels in a very large meta-analysis of 4 observational studies¹⁰⁸Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

Vitamin C levels

Our note: It is not unusual for different outcomes to be found between colon cancer and rectal cancer, and so lumping them together in one analysis does not always add clarity. This may be such a situation.

Preliminary evidence of lower risk of colon cancer among people with higher diet-derived circulating levels of vitamin C

24% lower risk of colon cancer among people with higher diet-derived circulating levels of vitamin C compared to lower in a combined analysis of 2 observational studies¹⁰⁹Zhang X, Zhao H et al. Investigating causal associations of diet-derived circulating antioxidants with the risk of digestive system cancers: a Mendelian randomization study. Nutrients. 2022;14(15):3237.

Preliminary (conflicting) of an effect on risk of colorectal cancer among people with genetically predicted higher levels of circulating vitamin C levels

45% lower risk of colorectal cancer among people with genetically predicted higher levels of circulating vitamin C compared to lower levels in a very large meta-analysis of 2 observational studies¹¹⁰Larsson SC, Mason AM et al. Circulating vitamin C and digestive system cancers: Mendelian randomization study. Clinical Nutrition. 2022;41(9):2031-2035.
No evidence of an effect on risk of colorectal cancer among people with genetically predicted higher levels of circulating ascorbate compared to lower levels in a very large observational study¹¹¹Yin L, Yan H et al. Diet-derived circulating antioxidants and risk of digestive system tumors: a Mendelian randomization study. Nutrients. 2022;14(16):3274.

Your genetics play a role in your vitamin C (ascorbate) levels. Many gene variants influence the production of proteins needed for transporting ascorbate. Some people naturally have genetically predicted higher levels of vitamin C, while other people have genetically predicted lower levels, which then influences susceptibility to some diseases.¹¹²Shaghaghi MA, Kloss O, Eck P. Genetic variation in human vitamin C transporter genes in common complex diseases. Advances in Nutrition. 2016 Mar 15;7(2):287-98.

Gastrointestinal cancer

Colorectal cancer and pancreatic cancer are listed separately.

No evidence of an effect on risk of esophageal, gastric, or liver cancers among people taking oral vitamin C in a combined analysis of studies

Modest evidence of greater regression of precancerous lesions among people with multifocal atrophic gastritis treated with oral vitamin C

Modest evidence of lower risk of esophageal cancer or Barrett’s esophagus—a risk factor for esophageal cancer—among people with the highest levels of dietary vitamin C intake

Preliminary evidence of lower risk of small intestine cancer among people with genetically predicted higher levels of circulating vitamin C

No evidence of an effect on risk of esophageal, stomach, or liver cancer among people with higher levels of vitamin C in several combined analyses of studies

Vitamin C supplements

No evidence of an effect on risk of esophageal, gastric, or liver cancers among people taking oral vitamin C in a combined analysis of studies

No evidence of an effect on risk of esophageal, gastric, or liver cancer among people taking oral vitamin C, either alone or with other antioxidant supplements, compared to placebo in very large 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 14 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 effects¹¹³Bjelakovic G, Nikolova D, Simonetti RG, Gluud C. Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis. Lancet. 2004;364(9441):1219-1228.

Modest evidence of greater regression of precancerous lesions among people with multifocal atrophic gastritis treated with oral vitamin C

Greater regression of multifocal nonmetaplastic atrophy among people with a preliminary histologic diagnosis of multifocal atrophic gastritis without intestinal metaplasia and dysplasia, but otherwise in good health, and greater regression of intestinal metaplasia among people with that condition, treated with 1 g ascorbic acid twice a day 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 large RCT;¹¹⁴Correa P, Fontham ET et al. Chemoprevention of gastric dysplasia: randomized trial of antioxidant supplements and anti-helicobacter pylori therapy. Journal of the National Cancer Institute. 2000 Dec 6;92(23):1881-8. multifocal nonmetaplastic atrophy and intestinal metaplasia are precancerous lesions

Dietary vitamin C

Modest evidence of lower risk of esophageal cancer or Barrett’s esophagus—a risk factor for esophageal cancer—among people with the highest levels of dietary vitamin C intake

Lower risk of esophageal cancer among people with the highest levels of dietary vitamin C intake compared to the lowest in a very large meta-analysis of 18 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 studies¹¹⁵Jia C, Lv X, Liu T, Yang L, Chen H. The association between dietary vitamin C intake and the risk of esophageal cancer: an updated dose-response meta-analysis. Nutrition and Cancer. 2022;74(10):3479-3491.
Lower risk of Barrett’s esophagus—a risk factor for esophageal cancer—among people with higher levels of vitamin C in their diets compared to low levels in a meta-analysis of 4 observational studies¹¹⁶Zhao Z, Yin Z, Zhang C. Lifestyle interventions can reduce the risk of Barrett’s esophagus: a systematic review and meta-analysis of 62 studies involving 250,157 participants. Cancer Medicine. 2021;10(15):5297-5320.

Vitamin C levels

Your genetics play a role in your vitamin C (ascorbate) levels. Many gene variants influence the production of proteins needed for transporting ascorbate. Some people naturally have genetically predicted higher levels of vitamin C, while other people have genetically predicted lower levels, which then influences susceptibility to some diseases.¹¹⁷Shaghaghi MA, Kloss O, Eck P. Genetic variation in human vitamin C transporter genes in common complex diseases. Advances in Nutrition. 2016 Mar 15;7(2):287-98.

Preliminary evidence of lower risk of small intestine cancer among people with genetically predicted higher levels of circulating vitamin C

45% lower risk of small intestine cancer among people with genetically predicted higher levels of circulating vitamin C compared to lower levels in a meta-analysis of 2 observational studies¹¹⁸Larsson SC, Mason AM et al. Circulating vitamin C and digestive system cancers: Mendelian randomization study. Clinical Nutrition. 2022;41(9):2031-2035.

No evidence of an effect on risk of esophageal, stomach, or liver cancer among people with higher levels of vitamin C in several combined analyses of studies

No evidence of an effect on risk of esophageal, stomach, or liver cancer among people with higher diet-derived circulating levels of vitamin C compared to lower in a combined analysis of 2 observational studies¹¹⁹Zhang X, Zhao H et al. Investigating causal associations of diet-derived circulating antioxidants with the risk of digestive system cancers: a Mendelian randomization study. Nutrients. 2022;14(15):3237.
No evidence of an effect on risk or mortality of stomach (gastric) cancer among people with higher plasma levels of vitamin C compared to lower levels in a large observational study¹²⁰Webb PM, Bates CJ, Palli D, Forman D. Gastric cancer, gastritis and plasma vitamin C: results from an international correlation and cross-sectional study. The Eurogast Study Group. International Journal of Cancer. 1997 Nov 27;73(5):684-9.
No evidence of an effect on risk of stomach (gastric), liver, or esophageal cancer among people with genetically predicted higher levels of circulating ascorbate compared to lower levels in a very large observational study¹²¹Yin L, Yan H et al. Diet-derived circulating antioxidants and risk of digestive system tumors: a Mendelian randomization study. Nutrients. 2022;14(16):3274.

Gynecologic cancer

Ovarian cancer is listed separately.

Preliminary evidence of a link between low vitamin C levels and risk of gynecologic cancer; we don’t know if low vitamin C levels contribute to cancer risk, or if having cancer leads to low vitamin C levels, or if the link works in both directions

Leukemia

Preliminary evidence of a link between low vitamin C levels and risk of leukemia; we don’t know if low vitamin C levels contribute to cancer risk, or if having cancer leads to low vitamin C levels, or if the link works in both directions

Lung cancer

Good evidencesignificant effects in one large or several mid-sized and well-designed clinical studies (randomized controlled trials (RCTs) with an appropriate placebo or other strong comparison control or observational studies that control for confounds) (this is the CancerChoices definition; other researchers and studies may define this differently) of lower risk of lung cancer among people with higher levels of vitamin C intake from diet, but no evidence of an effect on risk from vitamin C supplements

Weak evidence of lower risk of lung cancer among people with genetically predicted higher levels of circulating vitamin C

Vitamin C intake

Good evidence of lower risk of lung cancer among people with higher levels of vitamin C intake from diet, 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. on risk from vitamin C supplements

Lower risk of lung cancer risk among people with higher levels of vitamin C intake from diet (6 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), but no evidence of an effect on risk from vitamin C supplements (3 observational studies and 2 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) compared to lower levels in very large 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 study¹²⁴Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

Vitamin C levels

Your genetics play a role in your vitamin C (ascorbate) levels. Many gene variants influence the production of proteins needed for transporting ascorbate. Some people naturally have genetically predicted higher levels of vitamin C, while other people have genetically predicted lower levels, which then influences susceptibility to some diseases.¹²⁵Shaghaghi MA, Kloss O, Eck P. Genetic variation in human vitamin C transporter genes in common complex diseases. Advances in Nutrition. 2016 Mar 15;7(2):287-98.

Weak evidence of lower risk of lung cancer among people with genetically predicted higher levels of circulating vitamin C

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 lower risk of lung cancer among people with genetically predicted higher levels of circulating vitamin C compared to lower levels in a very large meta-analysis of observational studies¹²⁶Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

Melanoma and other skin cancers

No evidence of an effect on risk of sunburn—a risk factor for skin cancer—or cutaneous squamous cell carcinoma among people with higher intake of vitamin C

No evidence of an effect on risk of cutaneous squamous cell carcinoma among non-Hispanic whites with higher self-report vitamin C intake

Moderately lower risk of melanoma among people with the highest intake of vitamin C in their diets

No evidence of an effect on risk of sunburn—a risk factor for skin cancer—or cutaneous squamous cell carcinoma among people with higher intake of vitamin C

No evidence of an effect on risk of sunburn among people with higher intake of vitamin C compared to lower levels in a review of 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 trial¹²⁷Taylor JH, Rosen CF Systemic photoprotection. Current Dermatology Reports. 2020. 9:181–188. Taylor JH, Rosen CF. Correction to: Systemic photoprotection. Current Dermatology Reports. 2020;9(4):362. (see evidence of a protective effect when vitamin C is combined with vitamin E below)

No evidence of an effect on risk of cutaneous squamous cell carcinoma among non-Hispanic whites with higher self-report vitamin C intake

No evidence of an effect on risk of cutaneous squamous cell carcinoma among non-Hispanic whites with higher self-report vitamin C intake compared to lower levels of vitamin C in a 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 study¹²⁸Kim Y, Yin J et al. 255 Vitamin C and cutaneous squamous cell carcinoma risk: results from the genetic epidemiology research on adult health and aging cohort study 2007–2015 and Mendelian randomization analyses. Journal of Investigative Dermatology. 2022;142:8 (S43) Supplement.

Moderately lower risk of melanoma among people with the highest intake of vitamin C in their diets

41% lower risk of melanoma among people with the highest intake of vitamin C in their diets, and especially females under age 60, compared to the lowest in a large observational study¹²⁹Malavolti M, Malagoli C et al. Association between dietary vitamin C and risk of cutaneous melanoma in a population of Northern Italy. International Journal of Vitamin and Nutrition Research. 2013;83(5):291-298.

Mesothelioma

Preliminary evidence of a link between lower vitamin C levels and risk of mesothelioma; we don’t know if low vitamin C levels contribute to mesothelioma risk, or if having mesothelioma leads to low vitamin C levels, or if the link works in both directions

Multiple myeloma

Preliminary evidence of a link between lower vitamin C levels and risk of multiple myeloma; we don’t know if low vitamin C levels contribute to multiple myeloma risk, or if having multiple myeloma leads to low vitamin E levels, or if the link works in both directions

Ovarian cancer

No evidence of an effect on risk of ovarian cancer among women with higher dietary vitamin C intake in a large combined analysis of studies

Pancreatic cancer

No evidence of an effect on risk of pancreatic cancer among people taking oral vitamin C in a combined analysis of studies

No evidence of an effect on risk of pancreatic cancer among people with higher diet-derived circulating levels of vitamin C in a combined analysis of studies

Vitamin C supplements or dietary vitamin C

No evidence of an effect on risk of pancreatic cancer among people taking oral vitamin C in combined analyses of studies

No evidence of an effect on risk of pancreatic cancer among people taking vitamin C, either alone or with other antioxidant supplements, compared to placebo 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 14 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 effects¹³³Bjelakovic G, Nikolova D, Simonetti RG, Gluud C. Antioxidant supplements for prevention of gastrointestinal cancers: a systematic review and meta-analysis. Lancet. 2004;364(9441):1219-1228.
No evidence of an effect on risk of pancreatic cancer among people with genetically predicted higher levels of circulating ascorbate compared to lower levels in a 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 study¹³⁴Yin L, Yan H et al. Diet-derived circulating antioxidants and risk of digestive system tumors: a Mendelian randomization study. Nutrients. 2022;14(16):3274.
No evidence of an effect on prostate cancer risk among men eating the highest levels of foods with vitamin C or taking vitamin C supplements compared to the lowest levels in a very large observational study¹³⁵Kirsh VA, Hayes RB et al. Supplemental and dietary vitamin E, beta-carotene, and vitamin C intakes and prostate cancer risk. Journal of the National Cancer Institute. 2006;98(4):245-254.

Vitamin C levels

No evidence of an effect on risk of pancreatic cancer among people with higher diet-derived circulating levels of vitamin C in a combined analysis of studies

No evidence of an effect on risk of pancreatic cancer among people with higher diet-derived circulating levels of vitamin C compared to lower in a combined analysis of 2 observational studies¹³⁶Zhang X, Zhao H et al. Investigating causal associations of diet-derived circulating antioxidants with the risk of digestive system cancers: a Mendelian randomization study. Nutrients. 2022;14(15):3237.

Prostate cancer

No evidence of an effect on prostate cancer risk among people with higher levels of vitamin C intake from diet and/or supplements in very large studies

No evidence of an effect on prostate cancer risk among people with genetically predicted higher levels of circulating vitamin C levels in a very large analysis

Vitamin C supplements

No evidence of an effect on prostate cancer risk among people with higher levels of vitamin C intake from diet and/or supplements in very large studies

No evidence of an effect on risk of prostate cancer during 14 years of follow up among healthy men aged 50 or older treated with 500 mg of vitamin C daily for 10 years 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 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 effects¹³⁷Wang L, Sesso HD et al. Vitamin E and C supplementation and risk of cancer in men: posttrial follow-up in the Physicians’ Health Study II randomized trial. American Journal of Clinical Nutrition. 2014;100(3):915-923.
No evidence of an effect on prostate cancer risk among people with higher levels of vitamin C intake from diet and/or supplements compared to lower levels 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 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 studies¹³⁸Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

Vitamin C levels

Your genetics play a role in your vitamin C (ascorbate) levels. Many gene variants influence the production of proteins needed for transporting ascorbate. Some people naturally have genetically predicted higher levels of vitamin C, while other people have genetically predicted lower levels, which then influences susceptibility to some diseases.¹³⁹Shaghaghi MA, Kloss O, Eck P. Genetic variation in human vitamin C transporter genes in common complex diseases. Advances in Nutrition. 2016 Mar 15;7(2):287-98.

No evidence of an effect on prostate cancer risk among people with genetically predicted higher levels of circulating vitamin C levels in a very large analysis

No evidence of an effect on prostate cancer risk among people with genetically predicted higher levels of circulating vitamin C levels compared to lower levels in a very large combined analysis of observational studies¹⁴⁰Fu Y, Xu F et al. Circulating vitamin C concentration and risk of cancers: a Mendelian randomization study. BMC Medicine. 2021;19(1):171.

Dietary vitamin C

Preliminary evidence of lower risk of prostate cancer among men with the highest intake of vitamin C in foods

Lower risk of prostate cancer among men with the highest intake of vitamin C in foods compared to the lowest in a mid-sized observational study¹⁴¹McCann SE, Ambrosone CB. Intakes of selected nutrients, foods, and phytochemicals and prostate cancer risk in western New York. Nutrition and Cancer. 2005;53(1):33-41.

Vitamin C combined with other therapies

Weak evidence of lower cancer mortality among people without cancer at baseline eating the highest levels of antioxidants in foods

Preliminary evidence of lower risk of cervical cancer among women with the highest supplement and dietary intakes of vitamin A, beta -carotene, and vitamin C

Preliminary evidence of lower incidence of sunburn—a risk factor for skin cancer—among volunteers treated with vitamin C and vitamin E

No evidence of an effect on recurrence of colorectal polyps after removal of at least one colorectal polyp among people free of polyps treated with vitamins C and E

Modest evidence of greater regression of multifocal nonmetaplastic atrophy or intestinal metaplasia among people with multifocal atrophic gastritis without intestinal metaplasia and dysplasia treated with vitamin C (ascorbic acid) and beta-carotene

Weak evidence of normalization of CA-125 levels and no evidence of recurrence after cytoreduction surgery among 2 women with advanced epithelial ovarian cancer treated with oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10, and a multivitamin/mineral complex, plus intravenous vitamin C in addition to chemotherapy

Weak evidence of less redness/redness and the accompanying inflammation after exposure to ultraviolet radiation, risk factors for skin cancer, among healthy people treated with green tea catechins and vitamin C

Vitamin C combined with other antioxidants

Weak evidence of lower cancer mortality among people without cancer at baseline eating the highest levels of antioxidants in foods

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 lower cancer mortality among people without cancer at baseline eating the highest levels of antioxidants in foods compared to the lowest in a 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 study¹⁴²Sheng LT, Jiang YW, Pan A, Koh WP. Dietary total antioxidant capacity and mortality outcomes: the Singapore Chinese Health Study. European Journal of Nutrition. 2022;61(5):2375-2382.

Preliminary evidence of lower risk of cervical cancer among women with the highest supplement and dietary intakes of vitamin A, beta -carotene, and vitamin C

Lower risk of cervical cancer among women with the highest supplement and dietary intakes of vitamin A, beta -carotene, and vitamin C compared to lower levels, and lower levels of these antioxidants among people with cervical cancer compared to controls, in a mid-sized observational study¹⁴³Kim J, Kim MK et al. Intakes of vitamin A, C, and E, and beta-carotene are associated with risk of cervical cancer: a case-control study in Korea. Nutrition and Cancer. 2010;62(2):181-189.

Vitamin C with vitamin E

Preliminary evidence of lower incidence of sunburn—a risk factor for skin cancer—among volunteers treated with vitamin C and vitamin E

Lower incidence of sunburn among people treated with vitamin C and vitamin E compared to lower levels in a review of 3 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 trial¹⁴⁴Taylor JH, Rosen CF Systemic photoprotection. Current Dermatology Reports. 2020. 9:181–188. Taylor JH, Rosen CF. Correction to: Systemic photoprotection. Current Dermatology Reports. 2020;9(4):362.

No evidence of an effect on recurrence of colorectal polyps after removal of at least one colorectal polyp among people free of polyps treated with vitamins C and E

No evidence of an effect on recurrence of colorectal polyps, presumed precursors for colorectal cancer, after removal of at least one colorectal polyp among people free of polyps treated with vitamins C and E (ascorbic acid and alpha-tocopherol) 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 effects¹⁴⁵McKeown-Eyssen G, Holloway C et al. A randomized trial of vitamins C and E in the prevention of recurrence of colorectal polyps. Cancer Research. 1988 Aug 15;48(16):4701-5.

Vitamin C and beta-carotene: modest evidence of greater regression of multifocal nonmetaplastic atrophy or intestinal metaplasia among people with multifocal atrophic gastritis without intestinal metaplasia and dysplasia treated with vitamin C (ascorbic acid) and beta-carotene

Greater regression of multifocal nonmetaplastic atrophy among people with a preliminary histologic diagnosis of multifocal atrophic gastritis without intestinal metaplasia and dysplasia, but otherwise in good health, and greater regression of intestinal metaplasia among people with that condition, treated with 1 g ascorbic acid twice a day and 30 mg beta-carotene once per day compared to placebo in a large RCT;¹⁴⁶Correa P, Fontham ET et al. Chemoprevention of gastric dysplasia: randomized trial of antioxidant supplements and anti-helicobacter pylori therapy. Journal of the National Cancer Institute. 2000 Dec 6;92(23):1881-8. multifocal nonmetaplastic atrophy and intestinal metaplasia are precancerous lesions

Vitamin C combined with other antioxidants and chemotherapy: weak evidence of no recurrence after cytoreduction surgery among 2 women with advanced epithelial ovarian cancer treated with oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10, and a multivitamin/mineral complex, plus intravenous vitamin C in addition to chemotherapy

No evidence of recurrence after cytoreduction surgery among 2 women with advanced epithelial ovarian cancer treated with oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10, and a multivitamin/mineral complex, plus intravenous vitamin C in addition to chemotherapy in case studiesa descriptive and exploratory analysis of a person, group, or event regarding changes observed over time; because changes due to treatment are not compared to similar changes over time without treatment, a case study is considered a weak study design¹⁴⁷Drisko JA, Chapman J, Hunter VJ. The use of antioxidants with first-line chemotherapy in two cases of ovarian cancer. Journal of the American College of Nutrition. 2003 Apr;22(2):118-23.

Green tea and vitamin C: weak evidence of less redness/redness and the accompanying inflammation after exposure to ultraviolet radiation, risk factors for skin cancer, among healthy people treated with green tea catechins and vitamin C

Less redness (erythema) and the accompanying inflammation (12-hydroxyeicosatetraenoic acid) after exposure to UV radiation among healthy people treated with low-dose (540 mg) green tea catechins and 50 mg vitamin C daily for 12 weeks compared to baseline in a small uncontrolled trial¹⁴⁸Rhodes LE, Darby G et al. Oral green tea catechin metabolites are incorporated into human skin and protect against UV radiation-induced cutaneous inflammation in association with reduced production of pro-inflammatory eicosanoid 12-hydroxyeicosatetraenoic acid. British Journal of Nutrition. 2013 Sep 14;110(5):891-900.

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Last update: May 7, 2024

Last full literature review: January 2023

CancerChoices provides information about integrativein cancer care, a patient-centered approach combining the best of conventional care, self care, and evidence-informed complementary care in an integrated plan cancer care. We review complementaryin cancer care, complementary care involves the use of therapies intended to enhance or add to standard conventional treatments; examples include supplements, mind-body approaches such as yoga or psychosocialtherapy, and acupuncture therapies and self carelifestyle actions and behaviors that may impact cancer outcomes; examples include eating health-promoting foods, limiting alcohol, increasing physical activity, and managing stress practices to help patients and professionals explore and integrate the best combination of conventionalthe cancer care offered by conventionally trained physicians and most hospitals; examples are chemotherapy, surgery, and radiotherapy and complementary therapies and practices for each person.

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Vitamin C: Oral Use

How can oral vitamin C help you? What the research says

Improving treatment outcomes

Optimizing your body terrain

Vitamin C supplements

Vitamin C levels

Vitamin C supplements

Vitamin C levels

Vitamin C supplements

Vitamin C levels

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Vitamin C supplements

Managing side effects and promoting wellness

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Vitamin C’s role in cancer-related anemia

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