Dr. Abrams explains how the estrogen in soy compares to a woman's natural estrogen.
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I am Chief of Hematology/Oncology at San Francisco General Hospital and I completed the fellowship in Integrative Medicine at the University of Arizona in 2004. And since that time, I also have an integrative oncology consultation practice at the University of California, San Francisco Osher Center for Integrative Medicine. I am a professor of clinical medicine at the University of California, San Francisco. The plant estrogen, or phytoestrogen, in soy is much, much weaker than a woman’s own estrogen, but we do think that soy has many beneficial effects, particularly when consumed during puberty, for both men and women. If you look at Asians in Asia eating an Asian diet, which is becoming more rare with the globalization of food, we find that there’s a much lower risk of both breast and prostate cancer, and it’s felt that it’s probably due to exposure of these glands to soy, isoflavones or phytoestrogens, during development. Probably once somebody has developed in adult, the use of soy doesn’t decrease the risk of these cancers particularly. One of the concerns that people have had for a long time is, if these are plant estrogens and the woman has breast cancer that’s estrogen receptor positive, that is, it’s fueled by estrogen in the body, and she is post-menopausal, so doesn’t have a lot of her own estrogen, is it safe to consume a lot of soy products? And this is still an area of some controversy. The information keeps changing. There were some reports in the past that particularly women who were taking Tamoxifen, an estrogen receptor blocker, if you will, had trouble if they consumed a lot of soy products. Well now, just, just now, recently, a new report came out from the Life After Cancer Epidemiology study looking at thousands of women and concluding, actually, that soy in post-menopausal women or women with breast cancer taking Tamoxifen seems to improve outcomes, both the risk of breast cancer coming back as well as survival. So, you know I am sort of at a loss as to what to do because for a long time I have just been telling post-menopausal women who have estrogen receptor positive cancer not to consume too much soy, but now it seems like it might be okay, and in fact maybe beneficial, but the last article did say more studies are necessary. So, you know, in the meantime, probably the bottom line is that the amount of estrogen in soy foods is low enough that it doesn’t really matter. On the other hand, taking soy supplements or isoflavones supplements is something that I would be less inclined to advise people to do. Soy foods that are whole foods, like edamame or soybeans, tempeh, tofu, or soy milk are the best forms of soy. Soy that’s over processed like soy cheese, soy turkey, soy hot dogs, etcetera, becomes another heavily processed food or highly processed food, something that we should be avoiding in our diet in favor of more whole foods.