Exploring the Soy Controversy, Part 2
The Enigma of Soy for Health The widespread interest in the health benefits of the soybean has political, economic and social implications for Western society. Although the “meat and potatoes” diet has been a dominating force for years, the possibility of a major dietary switch from animal/dairy protein to vegetable protein (such as soy), is now a real prospect. However, the negative consequences of the typical American diet are eclipsed by the confusion surrounding the benefits of soy. In my view, these health benefits of soy need to be defined in the correct context.
The Isoflavone Debate When it comes to health, the most controversial components of soy are the isoflavones. The principal soy isoflavones, genistein and daidzein, appear to exert protective benefits for the body’s cells, especially if they are taken in early life. However, a small group of scientists have hypothesized that soy isoflavones may increase the risk of cancer in selected circumstances.
Population studies and animal experiments suggest that soy isoflavones have positive effects on breast, lung, stomach and bowel cell health. The notion that isoflavones may promote the growth of cancer in humans is merely an inference from the observations of the estrogenic actions of isoflavones on cancer tissue (in the lab), in animal experiments and in vitro studies; and estrogen dependent neoplasia has been studied in “nude mice” – a questionable scientific method. While there is a great deal of confusion regarding soy isoflavones, I have not seen any credible and concrete evidence that soy causes cancer in humans.
Dissecting the Actions of Isoflavones One simplistic and misleading point of view has been to categorize isoflavones as “phytoestrogens,” with potentially dangerous effects on estrogen levels in the body. The fact is, isoflavones can help balance out the effects of estrogen on body tissues, becoming pro- or anti-estrogenic to offset the effects of too little or too much of this hormone.
Versatility of isoflavones Soy isoflavones may exert protective benefits by functioning as antioxidants and seeking out free radicals. Experiments in animals and limited human observations show that isoflavones (specifically genistein) may positively affect angiogenesis (new blood vessel growth), a process associated with the spread of damaged cells. Thus, isoflavones have other protective benefits in addition to their effects on estrogen.
Appropriate Caution Megadoses of isoflavones are not advised. Although every body absorbs and processes soy differently, a safe dosage of isoflavones is approximately 80 mg/day of total isoflavones (in natural, conjugated format), but no more than 120 mg/day. These numbers are lower for highly absorbable forms of isoflavones, such as those found in fermented soy. I recommended no more than 45-60 mg of total isoflavones per day in fermented form.
Genetic Modification of Soy I save the worst news for the end of this short article. Soybeans have been genetically modified by the insertion of different genes. The genetic modification (GMO) of soy has occurred because of the perceived advantages of breeding crops with a built-in resistance to cold, herbicides and pesticides. Many health-conscious consumers are trying to purchase non-GMO soy but it can be difficult to find.
I have great uncertainty about the potential effects of genetically modified foods on the body. For this reason, I advise that individuals avoid genetically modified foods, including soy.
Be Healthy! Dr. Stephen Holt, M.D.