Flax and Breast Cancer Prevention

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Flax & Breast Cancer Prevention

Just a teaspoon of ground flaxseeds a day may help protect against breast cancer.

In 1980 a new compound was discovered in human urine. Researchers called it “compound X.” Originally it was thought to be a new human hormone, but it was soon identified as part of a large group of fiber-associated compounds widely distributed in edible plants known as lignans. Vegetarians have about twice the level of lignans circulating within their bodies given their greater intake of plant foods. Since population studies suggested that high intake of lignans reduces breast cancer risk, perhaps lignans are one of the reasons those eating plant-based diets have lower cancer rates.

Where are lignans found most in the diet? Seeds, whole grains, vegetables, fruits and berries. Since these are all really healthy foods in their own right, maybe lignan intake is just acting as a surrogate marker for whole plant food intake? (Like the fiber story I detail in Fiber vs. Breast Cancer). Well, in a petri dish lignans do directly suppress the proliferation of breast cancer cells but only after the plant lignans are converted into human lignans by the bacteria in our gut. (More detail in Flax & Fecal Flora).

That’s why we want to use antibiotics judiciously. A few days on antibiotics dramatically drops our body’s ability to make these anticancer compounds from the plants that we eat, and it can take weeks for our gut bacteria to recover. That may be why women with urinary tract infections have been found to be at higher risk for breast cancer. Every time they took a course of antibiotics they may have been stymying their good bacteria’s ability to take full advantage of all the plants they were eating.

In my 4-min video Flaxseeds & Breast Cancer Prevention I profile the National Cancer Institute study that provides the strongest evidence to date that there might indeed be something special about this class of phytonutrients for breast cancer prevention. They took a bunch of young women at high risk for breast cancer (meaning they had a suspicious breast biopsy showing either atypical hyperplasia or carcinoma in situ, or already had breast cancer in the other breast) and gave them a teaspoon of ground flaxseeds every day for a year before getting a repeat needle biopsy to see if there was any change.

Yes, there are lignans in sesame seeds, nuts, whole grains, legumes, certain fruits, and veggies, but they’re most concentrated in flax seeds. They could have instead asked women to eat ten cups of strawberries a day for a year to get the equivalent amount, but they’d probably get better compliance with just a teaspoon of flax :)

So what happened by the end of the year? The primary end point was the expression of a proliferation biomarker associated with cancer called ki-67. In 9 of the 45 women it went up, pictured in red in the video, but in the other 80% of the women it went down. And, indeed, on average they found less cellular proliferation in their breast tissue and fewer precancerous changes.

For those that don’t like the taste of flaxseeds, sesame seeds are also high in lignans. Even though flaxseeds have significantly more lignans than sesame, you appear to produce about the same amount of lignans from them. This was, however, comparing them whole. When people are fed whole flaxseeds, some may not be chewed up and can pass right through you. So ground flaxseed may be best overall. As I note in the Flaxseeds For Sensitive Skin video, ground flax stays fresh even at room temperature for at least a month.

What if you or a loved one has already been diagnosed with breast cancer? See my follow-up videos:

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, From Table to Able, and Food as Medicine.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

13 responses to “Flax & Breast Cancer Prevention

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  1. i encourgae you to look at the research at camelinaGold.com on camelinaGold oil and camaelinaGold seeds…
    it has a 2-1 ratio on the omega 3 and 6…. that is better than flax…in comparison flax has a 3-1 ratio and once you open the flax oil you only have a month to use it… with camelinaGold you have a 2 year shelf life…

    and camelinaGold oils have also been used for pediatric skin care and treatment of sclerosis… it gives you 101% of daily vitamin E…doctors at OHSU are recommending it to post cancer treatment patients …
    my doctor told me i should switch to camelinaGold oils and seeds instead of using flax..i use camelinaGold everywhere i would us flax or chia …

    it is worth comparing,,, and it is much more economical.. about half the cost…don’t take my word for it… look at the studies… :) good health to you all…

  2. Another great report that validates the many dietary changes I’ve made over the years. When I make my own granola, I always add a third of a cup or so of ground flaxseed.

  3. I had breast cancer 12 years ago at age 53- caused, in part, by 2 years on bio-identical hormones. I had a lumpectomy and then chose not to do any other therapy- no chemo, radiation, etc. I am doing great! Flax seed, (ground fresh daily and eaten cool) nettle tea, St. John’s tea and turmeric are all helpful. Plus less stress, more sleep, moderate exercise, lots of vegetables, etc. NO MORE chemicals or drugs! Danielle
    PS Started skiing Taos mountain at age 57! Still going strong. I am a breast cancer ALUMNI!

  4. Thank you for the article, this is really interesting! I am hoping that I can ask for some advice… My wife suffered from ER+ (HER2) breast cancer 5 years ago. She is doing great now :) but we are always worried about recurrence risk. We have recently moved to an entirely plant-based diet and (having read How Not To Die) have incorporated flax seed meal into our diet. However, there is some conflicting advice regarding this. For example, the below website recommends against flax for those with a history of ER+ breast cancer.
    I am learning what sources are reliable and which aren’t but this scared me a little as the site seems legitimate. Any advice would be greatly appreciated – thank you!!

  5. Hi, Darren. I understand your concern. It can be very confusing to look for health information on the internet, as there are often conflicting positions and it can be difficult to decide which sources are credible. You may be reassured by this 2014 systematic review of medical literature regarding flax and breast cancer:
    The authors concluded, “Current evidence suggests that flax may be associated with decreased risk of breast cancer. Flax demonstrates antiproliferative effects in breast tissue of women at risk of breast cancer and may protect against primary breast cancer. Mortality risk may also be reduced among those living with breast cancer.”
    I hope that helps!

  6. I’m not sure if you can answer this question. If flax affects the level of estrogen in your body could it decrease the effectiveness of oral contraceptives? Thanks,Karen

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