Transcript: Flax Seeds & Breast Cancer Prevention
A 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.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Ariel Levitsky.
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