Flax Seeds & Breast Cancer Prevention

Flax Seeds For Breast Cancer PreventionA quarter century ago, a theory was put forth as to why those eating plant-based diets have lower cancer rates. Vegetarians appeared to have about twice the level of lignans circulating within their bodies, related to the amount of grains and other plant foods they were eating. Back in 1980 a new compound was described in human urine, a compound X, originally thought to be a new human hormone, but later identified to be from a large group of fiber-associated compounds widely distributed in edible plants known as lignans. Population studies suggest that high intake reduces breast cancer risk, but where’s it found?

Seeds, whole grains, vegetables, fruits and berries. So why isn’t it just like the fiber story where lignan intake is just a surrogate marker for healthy plant food intake. 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. That’s why we want to use antibiotics judiciously, because a few days on antibiotics dramatically drops your 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’s why women with urinary tract infections may be at higher risk for breast cancer, because every time they took a course of antibiotics they were stymying their good bacteria’s ability to take full advantage of all the plants they were eating, though this remains little more than a hypothesis or educated guess at this point.

This is the National Cancer Institute study that provided the strongest evidence to date that there may 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, 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, those in red, 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 may work just as well. Even though flaxseeds have significantly more lignans than sesame, you appear to produce about the same amount of lignans from them, though this was comparing them whole, and when you feed people whole flaxseeds some may not get chewed and they can pass right through you, so ground flaxseed may be best.

Doctor’s Note

Today starts a three-part video series on the role flaxseeds may play in the prevention and treatment of breast cancer. I covered their role in prostate cancer in Flaxseed vs. Prostate Cancer and Was It the Flaxseed, Fat Restriction, or Both?. Then for blood sugar control (Flaxseed vs. Diabetes) and skin health (Flaxseeds For Sensitive Skin).

When I say “why isn’t it just like the fiber story” I’m referring to the previous video Fiber vs. Breast Cancer. The graph comparing the lignan contents of various foods is from this video: Breast Cancer Survival and Lignan Intake. Sorry if I covered the UTI-breast cancer connection a little fast—more background on the role our good bacteria play in Flax and Fecal Flora. 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, though? Hopefully you’ll find the next two videos useful: Flaxseeds & Breast Cancer Survival: Epidemiological Evidence and Flaxseeds & Breast Cancer Survival: Clinical Evidence.

For some context, please also check out my associated blog posts: Treating Sensitive Skin From the Inside OutFlax and Breast Cancer Prevention , and Flax and Breast Cancer Survival  

Featured Photo Source: barbaramendeznutrition.com

Michael Greger M.D.About Michael Greger M.D.Michael Greger, M.D., is a physician, 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. Currently Dr. Greger proudly serves as the Director of Public Health and Animal Agriculture at the Humane Society of the United States.

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  1. Christine Baldwin says:

    This does not address whether or not flaxseed should be eaten by women with hormone positive breast cancer. I have read and been told conflicting advice about this, because flax is a phytoestrogen. I used to eat ground flaxseed daily, but now I’m hesitant.


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