Transcript: Flax Seeds & Breast Cancer Survival: Epidemiological Evidence
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
The class of phytonutrients known as lignans can be thought of as the Western equivalent of the isoflavone phytoestrogens, found in soy foods, popular in traditional Asian diets—as they share many of the same purported anti-cancer properties. Since, as we’ve explored, soy food consumption is associated with both preventing breast cancer, and prolonging breast cancer survival, one might expect the same to be found for lignans.
Well, we just covered the prevention angle, with population-based evidence, in-vitro evidence, and clinical evidence supporting lignans in preventing breast cancer. But, what about for women already diagnosed with the dreaded disease?
Three studies, following a total of thousands of women diagnosed with breast cancer, were recently published to answer that question. The first was from New York, reporting substantially reduced risks of overall mortality, and especially breast cancer mortality, associated with higher lignan intakes in postmenopausal women. “…[A]lthough higher lignan intakes may just be a marker of a diet high in plant foods, specific combinations of foods particularly high in lignans may be necessary to produce effects on mortality-related risk factors to subsequently impact [breast cancer] survival.”
Then there was one out of Italy, in 2012. At surgery, when the women were getting their primary breast tumors removed, they had some blood drawn, and within five years, those that had lower circulating levels of lignans (here in blue) were significantly more likely to die from their cancer coming back than those with more lignans in their bloodstream (in red). They concluded, “lignans might play an important role in reducing all-cause and cancer-specific mortality of the patients operated on for breast cancer.”
And, same thing out of Germany. The latest and largest study to date: “Postmenopausal patients with breast cancer who have high serum [lignan] levels may have better survival.” Here’s the survival curve; the higher the better. Those who had the most lignans in their bodies tended to live the longest, and tended to live the longest disease-free.
So, what should oncologists tell their patients? “Given this objective evidence that [blood levels of lignans] a biomarker of lignan intake improves breast cancer outcomes, should we declare success and recommend that our patients with breast cancer supplement their diet with flaxseed?” Not based on laboratory and population evidence alone, the editorial concluded; robust clinical evidence is needed—which I’ll cover in the next video.
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