Fighting breast cancer with flaxseeds

What are lignans?

Plant lignans are one of the four classes of phytoestrogens (isoflavones, lignans, stilbenes, coumestans), phenolic compounds that are structurally similar to the main mammalian estrogen, estradiol.1 Plant lignans are modified by bacteria in the human digestive tract into enteroligans. It is important to recognize the role of healthy bacteria in this process, because antibiotics can destroy beneficial bacteria in the gut resulting in long-term reduction in enteroligans.2 Eating commercial meats exposes us to antibiotics, as does the overuse and inappropriate prescribing by physicians.

Which foods are good sources of plant lignans?


Flaxseeds are the richest source of plant lignans, having about 8 times the lignan content of sesame seeds [note that flaxseed oil does not contain lignans – 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 Chia seeds are also a rich source of lignans.

• Flaxseeds (85.5 mg/ounce)
Sesame seeds (11.2 mg/ounce)4
• Kale (curly; 1.6 mg/cup)
• Broccoli (1.2 mg/cup)

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 reduced risk of hormone-related cancers.2,5 Enterolignans inhibits aromatase6 and estradiol production in general, lowering serum estrogen levels.7 Plant lignans also increase concentration of sex hormone binding globulin, which blunts the effects of estrogens.8-10 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.11

In a mouse model, a flaxseed diet (5%, 10%) shows dose-dependent inhibition of breast tumor growth.12 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 imbedded or 25g flax-containing muffin starting at time of diagnosis of breast cancer for just 32-39 days until surgery. Tumor tissue analyzed at diagnosis and surgery demonstrated surprising benefits even in this short timeframe. There was a significant apoptosis (tumor cell death) and reduced cell proliferation in the flaxseed group in just the one month.13 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 percent) reduction in all causes of death.14,15 Flaxseeds are clearly super foods; even with a mediocre diet they offer powerful protection against certain types of 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. The intake of dried beans was also associated with a 39% reduced risk of all-cause mortality.16 Endometrial and ovarian cancer have not been as extensively studied, but the few studies that have been conducted suggest a protective effect.2,17

Bottom line; don’t forget to take your ground flax seeds (or chia seeds) every day. I sometimes forget too, but reviewing the science encourages me to remember. When used in conjunction with dietary exposure to greens, onions, mushrooms and beans, dramatic reductions in the risk of breast cancer are possible.


My book, Super Immunity, addresses my full nutritional program to win the war against breast cancer.



1. Mense SM, Hei TK, Ganju RK, et al: Phytoestrogens and breast cancer prevention: possible mechanisms of action. Environ Health Perspect 2008;116:426-433.
2. Higdon J: Lignans. In An Evidence-Based Approach to Dietary Phytochemicals. New York: Thieme; 2006: 155-161
3. 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.
4. 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.
5. Adlercreutz H: Lignans and human health. Crit Rev Clin Lab Sci 2007;44:483-525.
6. 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.
7. 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.
8. 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.
9. 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.
10. 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.
11. 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.
12. 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.
13. 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.
14. Buck K, Vrieling A, Zaineddin AK, et al: Serum enterolactone and prognosis of postmenopausal breast cancer. J Clin Oncol 2011;29:3730-3738.
15. 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.
16. 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.
17. 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 Womens Health 2011;11:40.



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Comments (13) Read through and enter the discussion with the form at the end
Denise D'Agostino - November 30, 2011 12:31 PM

As always, astounding information. I'm so happy that studies are now being conducted on the effects of these foods! :) The connections made are so clear. Thanks for your work Dr. F! Hopefully with your work, nutritional prescriptions will become the norm :)

Paul B - November 30, 2011 3:37 PM

Just a reminder, the recommended dose it 1 tablespoon of whole flax that is then ground for those on ETL, right? Nutritarians at goal weight could have more. Correct?


Mark Osborne - November 30, 2011 5:44 PM

Interesting post, I was aware of the Omega-3 benefits of flax and chia - but wasn't aware of the pytoestrogen content.

There still seems to be some controversy around phytoestrogens on the net. Some people (that I am less inclined to trust than Dr Fuhrman) are agressively pushing the opinion that soy is bad for you due to its pytoestrogen content among other reasons.

Incidentally these same people also claim that fermented soy is OK - which is odd, because fermentation makes the pytoestrogens more bioavailable (aglycone isoflavones are absorbed faster and in greater amounts than their glucosides).

Michelle Berkovitz - November 30, 2011 7:08 PM

I take 2 T ground flax daily because I can control hot flashes that way. 1 T was not enough.

Thanks for your work, Dr. F.

Theresa Anderson - December 1, 2011 2:08 AM

Thank you for the reminder of how potent accurate eating directions can be proven out to be. Not complicated either!

TMR - December 1, 2011 5:16 AM

I would really like to share this article, but due to the fact that you include animal torture in it, I cannot. Any chance you could cease putting references to animal experimentation in your pieces?

abb - December 1, 2011 11:29 AM

Could you comment on hemp seeds relative to this discussion? I was under the impression from a discussion on the member center some time ago that hemp seeds could be used as an alternative to flax seeds. If not the case, could you comment on their value? Thank you!

Deana Ferreri, Ph.D. - December 1, 2011 4:59 PM

The lignan content of hemp seeds has not yet been reported. For omega-3 content, hemp seeds are similar to flaxseeds (1.0 and 1.6 grams of ALA, respectively)

Diana Robertson - December 1, 2011 10:51 PM

I agree with TMR, due to your reference to a "mouse model"(tormenting animals in the name of science) I don't feel comfortable recommending or sharing this article....Dr. Fuhrman, hope you will in future utilize human trials &/or computer models only.....thank you!

JenLamSis - December 2, 2011 1:23 AM

I've been eating Nutritarian since Jan. I've discovered that severe psoriatic arthritis flares were being caused by nightshades and other foods with solanine (blueberries, apples, artichoke and okra).

I've been trying to find the causality of this and came across information about intestinal permeability and lignans being a possible problem crossing the intestinal wall. Can anyone shed light on this?

I've been soaking beans & rice, and was considering soaking nuts. What about flax seeds?

Fredrik Fälth - December 3, 2011 7:32 AM

In discussions regarding flax seeds, a counter argument often comes up, that I haven't been able to confirm, nor debunk. I you could comment, I would be grateful.

In short, flax seeds are claimed to contain a poison (sometimes cyanide has been mentioned). The poison would countact all benefits from flax seeds, and thus we are NOT recommended to eat flax seeds. Flax seed oil is OK, though.

Is there a poison in flax seed?
Are there any peer reviewed articles about negative effects from consuming flax seeds?
Is there a highest recommended daily dose of flax seeds because of this poison, or other reasons?


Laura - December 20, 2011 10:19 AM

Funny how I still see information out there cautioning that foods like flax contribute to cancer due to plant estrogens.

Claudia - December 25, 2011 10:52 AM

I am wondering whether or not we need to go for the food that is the very highest in lignans (flaxseed), or whether other nuts and seeds still have more than enough to give us the same cancer fighting effect. Do we know if there is an optimal amount of lignans, beyond which there isn't any additional protection from cancer?

The article states that an ounce of flaxseeds has 8 times the lignan content of an ounce of sesame seeds, but I think we need to remember that it is okay to eat a whole ounce of sesame seeds, but not necessarily okay to eat a whole ounce of ground flaxseed (this would be about 4 TBSP of ground flaxseed). Of course even 1 TBSP of ground Flax would still have twice the lignan content of an ounce of sesame seeds, but still it seems that the sesame seeds might still be an excellent choice. This of course brings me back to my original question. Namely, do we know if there is an optimal amount of lignans beyond which there isn't any additional protection from cancer? Will eating sesame seeds, or other nuts and seeds give us the same cancer fighting effect as has been demonstrated for flaxseed?

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