Soy products are heavily promoted in American as being a healthy food choice. The U.S. Food and Drug Administration approved a health claim in 1999 for food labels that a daily diet containing 25 grams of soy protein, also low in saturated fat and cholesterol, may reduce the risk of heart disease, which has made soy seem attractive to many people. But there are some definite concerns about using soy products.
Soy and Estrogen Dominiance
Dr. Michael Lam is a specialist in preventive and anti-aging medicine, and the author of "Estrogen Dominance - Hormonal Imbalance of the 21st Century." Estrogen dominance is a relative excess of estrogen and a deficiency in progesterone. According to Lam, estrogen dominance syndrome approaches 50 percent in western women over 35 years old, and soy products can make it worse. He notes that in Asia people commonly ferment soy into something like miso, tempeh or natto, and eat it as an adjunct to animal protein rather than as the primary source of protein. Perhaps most importantly, Lam says, they use soy as a condiment only, and it comprises a very small part of the Asian diet. Total calorie intake from soy in China is about 1.5 percent of the diet. In Japan, a typical meal for a man might include 8 g or 2 tsp. of soy, as compared to an American man who might ingest 8 oz. or 220 g of soy as tofu and soy milk, neither of which are fermented.
Soy Isoflavones
Soy is quite complex, containing protein, fatty acids, and a group of compounds called isoflavones; the latter are phytoestrogens, meaning plant substances that act like estrogen in the human body. Of these, genistein is of particular concern; soy milk, which is not fermented, contains genistein. Both amounts and fermentation matter, says Lam. Japanese may consume only 10 mg of soy a day, but a soy burger can easily bring the total intake to 200 mg. Soy which has not been fermented, Lam notes, also contains phylates, which block the body's absorption of minerals, contains enzyme inhibitors that reduce protein digestion, and lacks calcium.
Research Review
The Agency for Healthcare Research and Quality has reviewed all the studies on soy and notes that there is no evidence to support an effect of soy products on the function of the endocrine glands, menstrual cycle length or bone health -- all of which are tied to estrogen activity in women. But it says using soy as an alternative to estrogen therapy is risky because its phytoestrogens may promote tumor recurrence in breast cancer survivors.
Considerations and Warnings
The bottom line, says Lam, is that estrogen is involved in a number of diseases such as breast cancer, and it is wise not to ingest foods that could potentially have an estrogen effect in the body. If you use soy milk on a regular basis, or are considering adding it to your diet, it would be wise to discuss this issue with a health care practitioner.
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