Want to fight against breast cancer? Lignans in flax and chia seeds lower the risk of breast cancer. So, eating flax and chia seeds can help, according to RD&T contributor Joel Fuhrman, M.D.
The old adage, “An ounce of prevention is worth a pound of cure,” best describes what our focus should be regarding breast cancer, which is the most common form of cancer that affects women and is the second leading cause of death for women after heart disease. While a great deal of money and attention is focused on breast cancer awareness, it would make more sense to concentrate on preventing the disease from occurring in the first place.
There are nutritional strategies that are safe, easily implemented, and have been proven effective in reducing the risk of breast cancer.
A Great Breast Cancer Fighter
Among the most powerful anti-cancer foods are flax and chia seeds, which are a rich source of lignans. Lignans have anti-estrogenic effects that inhibit cell growth in breast tumors.
Lignans in a High-Nutrient Diet
Let’s take an in-depth look at lignans and why they are so effective in combating breast cancer:
- Plant lignans are one of the four classes of phytoestrogens (isoflavones, lignans, stilbenes, coumestans).
- Phytoestrogens are a group of chemicals found in plants that can act like the hormone estrogen.
- In particular, lignans are structurally similar to the main mammalian estrogen, estradiol.1
- Plant lignans are modified by bacteria in the human digestive tract into enteroligans.
Anti-Cancer Effects of Lignans
Enterolignans are structurally similar to estrogen and can bind to estrogen receptors. This capability allows lignans to either have weak estrogenic activity or block the actions of estrogen in the body. For this reason, plant lignans are classified as phytoestrogens, and there has been much interest in the potential contribution of lignan-rich foods to a reduced risk of hormone-related cancers.2,6
It is important to recognize the role of healthy bacteria in this process because antibiotics can destroy beneficial bacteria in the gut, resulting in a long-term reduction in enteroligans.2 Eating commercial meats expose us to antibiotics, as does the overuse and inappropriate prescribing of these drugs by physicians.
Best Sources of Plant Lignans
Flaxseeds are the richest source of plant lignans, having about three times the lignan content of chia seeds, and eight times the lignan content of sesame seeds. It is important to note that flaxseed oil does not contain lignans, because they bind to the fiber. The other plant foods on the list have about one-tenth or less the amount of lignans as sesame seeds per serving.2-3
- Flaxseeds (85.5 mg/ounce)
- Chia seeds (32 mg/ounce)4
- Sesame seeds (11.2 mg/ounce)5
- Kale; curly (1.6 mg/cup)
- Broccoli (1.2 mg/cup)
Enterolignans inhibits aromatase7 and estradiol production in general, lowering serum estrogen levels.8 Plant lignans also increase the concentration of sex hormone-binding globulin, which blunts the effects of estrogens.9-11 These benefits were documented when 48 postmenopausal women consumed 7.5 g/day of ground flax seeds for 6 weeks, then 15 g for 6 weeks – and significant decreases in estradiol, estrone, and testosterone were noted, with a bigger decrease in overweight and obese women.12
In a mouse model, a flaxseed diet (5%, 10%) shows dose-dependent inhibition of breast tumor growth.13 Human trials also confirmed similar beneficial effects. A double-blinded, randomized controlled trial of dietary flaxseed demonstrated dramatic protection.
Women ate either a control muffin with no flax seeds embedded or a 25g flax-containing muffin, starting at the time of diagnosis of breast cancer for just 32-39 days until surgery. Tumor tissue analyzed at diagnosis and then at the time of surgery demonstrated surprising benefits even in this short time frame. There was significant apoptosis (tumor cell death) and reduced cell proliferation in the flaxseed group in just the one month.14
Likewise, women eating more flaxseeds with a documented higher serum enterolactone were found to have a 42% reduced risk of death from postmenopausal breast cancer and a dramatic 40% reduction in all causes of death.15-16
Flaxseeds are clearly superfoods; even with a mediocre diet, they offer powerful protection against breast cancer. Another interesting study on flax followed women for up to 10 years and found a 51% reduced risk of all-cause mortality, and a 71% reduced risk of breast cancer mortality.
In addition, the intake of dried beans was associated with a 39% reduced risk of all-cause mortality.17 Endometrial and ovarian cancer have not been as extensively studied, but the few studies that have been conducted suggest a protective effect.2,18
Bottom line: Don’t forget to take your ground flax seeds (or chia seeds) every day. When used in conjunction with dietary exposure to greens, onions, mushrooms, and beans, dramatic reductions in the risk of breast cancer are possible.
- Mense SM, Hei TK, Ganju RK, et al: Phytoestrogens and breast cancer prevention: possible mechanisms of action. Environ Health Perspect 2008; 116: 426-433.
- Higdon J: Lignans. In An Evidence-Based Approach to Dietary Phytochemicals. New York: Thieme; 2006: 155-161.
- Milder IE, Arts IC, van de Putte B, et al: Lignan contents of Dutch plant foods: a database including lariciresinol, pinoresinol, secoisolariciresinol and matairesinol. Br J Nutr 2005; 93: 393-402.
- Nemes SM, Orstat V: Evaluation of a Microwave-Assisted Extraction Method for Lignan Quantification in Flaxseed Cultivars and Selected Oil Seeds. Food Analytical Methods 2012; 5: 551-563.
- Coulman KD, Liu Z, Hum WQ, et al: Whole sesame seed is as rich a source of mammalian lignan precursors as whole flaxseed. Nutr Cancer 2005; 52: 156-165.
- Adlercreutz H: Lignans and human health. Crit Rev Clin Lab Sci 2007; 44: 483-525.
- Adlercreutz H, Bannwart C, Wahala K, et al: Inhibition of human aromatase by mammalian lignans and isoflavonoid phytoestrogens. J Steroid Biochem Mol Biol 1993; 44: 147-153.
- Brooks JD, Thompson LU: Mammalian lignans and genistein decrease the activities of aromatase and 17beta-hydroxysteroid dehydrogenase in MCF-7 cells. J Steroid Biochem Mol Biol 2005; 94: 461-467.
- Adlercreutz H, Mousavi Y, Clark J, et al: Dietary phytoestrogens and cancer: in vitro and in vivo studies. J Steroid Biochem Mol Biol 1992; 41: 331-337.
- Adlercreutz H, Hockerstedt K, Bannwart C, et al: Effect of dietary components, including lignans and phytoestrogens, on enterohepatic circulation and liver metabolism of estrogens and on sex hormone binding globulin (SHBG). J Steroid Biochem 1987; 27: 1135-1144.
- Low YL, Dunning AM, Dowsett M, et al: Phytoestrogen exposure is associated with circulating sex hormone levels in postmenopausal women and interact with ESR1 and NR1I2 gene variants. Cancer Epidemiol Biomarkers Prev 2007; 16: 1009-1016.
- Sturgeon SR, Heersink JL, Volpe SL, et al: Effect of dietary flaxseed on serum levels of estrogens and androgens in postmenopausal women. Nutr Cancer 2008; 60: 612-618.
- Chen J, Power KA, Mann J, et al: Flaxseed alone or in combination with tamoxifen inhibits MCF-7 breast tumor growth in ovariectomized athymic mice with high circulating levels of estrogen. Exp Biol Med (Maywood) 2007; 232: 1071-1080.
- Thompson LU, Chen JM, Li T, et al: Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Clin Cancer Res 2005; 11: 3828-3835.
- Buck K, Vrieling A, Zaineddin AK, et al: Serum enterolactone and prognosis of postmenopausal breast cancer. J Clin Oncol 2011; 29: 3730-3738.
- Buck K, Zaineddin AK, Vrieling A, et al: Estimated enterolignans, lignan-rich foods, and fibre in relation to survival after postmenopausal breast cancer. Br J Cancer 2011; 105: 1151-1157.
- McCann SE, Thompson LU, Nie J, et al: Dietary lignan intakes in relation to survival among women with breast cancer: the Western New York Exposures and Breast Cancer (WEB) Study. Breast Cancer Res Treat 2010; 122: 229-235.
- Bandera EV, King M, Chandran U, et al: Phytoestrogen consumption from foods and supplements and epithelial ovarian cancer risk: a population-based case control study. BMC Women’s Health 2011; 11: 40.