Flaxseed

Dietary flaxseed: preliminary evidence of anticancer action among people with breast cancer eating flaxseed

• Less tumor cell proliferation, lower markersa chemical or substance, such as certain proteins or genetic material, that are associated with the presence of cancer or a change in status or prognosis; these markers can be detected in blood, urine, or tissue. Tumor markers are not direct measures of clinical outcomes such as survival or metastasis, and if a therapy or treatment shows an impact only on tumor markers, we cannot surmise that it will affect survival. of cell growth, and higher cell death (apoptosis), among postmenopausal women with newly diagnosed breast cancer eating flaxseed compared to placebo 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 effects¹Thompson LU, Chen JM, Li T, Strasser-Weippl K, Goss PE. Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Clinical Cancer Research. 2005 May 15;11(10):3828-35.

Flaxseed supplements: weak evidence of anticancer action among women at risk for breast cancer after supplementation with a lignan found in flax

• Lower levels of a for tumor cell proliferation in benign breast tissue of premenopausal women at risk for breast cancer after supplementation with a lignan found in flax 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 design²Fabian CJ, Kimler BF, et al. Reduction in Ki-67 in benign breast tissue of high-risk women with the lignan secoisolariciresinol diglycoside. Cancer Prevention Research. 2010 Oct;3(10):1342-50.

• Lower proliferation rates but no change in cell death (apoptosis) or cancer biomarkersa chemical or substance, such as certain proteins or genetic material, that are associated with the presence of cancer or a change in status or prognosis; these markers can be detected in blood, urine, or tissue. Tumor markers are not direct measures of clinical outcomes such as survival or metastasis, and if a therapy or treatment shows an impact only on tumor markers, we cannot surmise that it will affect survival. before surgery among men with prostate cancer adding flaxseed to their diets compared to controls in a mid-size RCTrandomized controlled trial, a study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects of moderate quality³Demark-Wahnefried W, Polascik TJ et al. Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. Cancer Epidemiology, Biomarkers & Prevention. 2008 Dec;17(12):3577-87; Hackshaw-McGeagh LE, Perry RE et al. A systematic review of dietary, nutritional, and physical activity interventions for the prevention of prostate cancer progression and mortality. Cancer Causes and Control. 2015 Nov;26(11):1521-50.
• 23% lower levels of a tumor biomarker among men with localized prostate cancer adding ground flaxseed to their diets for 30 days compared to controls in a mid-sized RCT⁴Azrad M, Vollmer RT et al. Flaxseed-derived enterolactone is inversely associated with tumor cell proliferation in men with localized prostate cancer. Journal of Medicinal Food. 2013 Apr;16(4):357-60.

Dietary flaxseed: modest evidence of better markers of blood sugar and insulin sensitivity among people adding flaxseed to their diets

• Better blood sugar control and insulin levels and sensitivity among people eating whole flaxseed for 12 weeks or more 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 12 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 effects⁵Mohammadi-Sartang M, Sohrabi Z, Barati-Boldaji R, Raeisi-Dehkordi H, Mazloom Z. Flaxseed supplementation on glucose control and insulin sensitivity: a systematic review and meta-analysis of 25 randomized, placebo-controlled trials. Nutrition Reviews. 2018 Feb 1;76(2):125-13.
• Lower fasting plasma glucose, but no change in plasma insulin, among glucose-intolerant people with obesity adding ground flaxseed to their diets for 12 weeks compared to controls adding wheat bran in a small RCT⁶Rhee Y, Brunt A. Flaxseed supplementation improved insulin resistance in obese glucose intolerant people: a randomized crossover design. Nutrition Journal. 2011 May 9;10:44.
• Better peak blood glucose levels among healthy people after eating flax bread compared to white bread in a small RCT⁷Dahl WJ, Lockert EA, Cammer AL, Whiting SJ. Effects of flax fiber on laxation and glycemic response in healthy volunteers. Journal of Medicinal Food. Winter 2005;8(4):508-11.

Flaxseed 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 blood sugar or insulin sensitivity among people using flaxseed oil and lignan extract in a combined analysis of studies

• No change in blood sugar control, insulin levels and sensitivity among people using flaxseed oil and lignan extract compared to controls in a meta-analysis of 12 RCTs⁸Mohammadi-Sartang M, Sohrabi Z, Barati-Boldaji R, Raeisi-Dehkordi H, Mazloom Z. Flaxseed supplementation on glucose control and insulin sensitivity: a systematic review and meta-analysis of 25 randomized, placebo-controlled trials. Nutrition Reviews. 2018 Feb 1;76(2):125-13.

• Lower testosterone and estrone among postmenopausal women without cancer who are obese after eating ground flaxseeds compared to baseline in a small observationala type of study in which individuals are observed or certain outcomes are measured, but no attempt is made to affect the outcome (for example, no treatment is given); an example is a study that records people’s diets, but doesn’t try to alter their diets, and looks for patterns of disease or other outcomes related to different foods study, and 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 levels of estradiol, estrone, and testosterone among postmenopasual women without cancer who are not obese⁹Sturgeon SR, Heersink JL et al. Effect of dietary flaxseed on serum levels of estrogens and androgens in postmenopausal women. Nutrition and Cancer. 2008;60(5):612-8.