Soy and health: Benefits and controversies - Mark Messina, PhD, MS




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During the past 25 years the health effects of soyfoods have been extensively evaluated. Much of this research has been conducted because the soybean is a uniquely-rich source of isoflavones, non-steroidal molecules classified as both phytoestrogens and selective estrogen receptor modulators. However, soyfoods are not without controversy, as the estrogen-like effects of isoflavones have raised concerns that soyfoods may for example, worsen the prognosis of breast cancer patients, feminize men, and cause abnormal development in boys and girls. Importantly, most of the concerns are based primarily on research conducted in rodents or are derived from case studies in which participants consumed excessive amounts of soyfoods or isoflavones whereas benefits are based on clinical and epidemiologic data. For example, rodent research shows that isoflavone-containing products stimulate the growth of existing mammary tumors in athymic ovariectomized mice implanted with estrogen-sensitive breast cancer cells whereas prospective epidemiologic research involving over 11,000 breast cancer patients shows post-diagnosis isoflavone intake reduces recurrence and breast cancer-specific mortality. Also, although two case reports each noted feminizing effects in individual males, these effects occurred in response to the consumption of approximately 12 servings of soyfoods per day. In contrast, feminizing effects have not been noted in the large number of clinical studies that have evaluated the effects of isoflavone exposure on reproductive hormone levels and sperm and semen parameters. This presentation will evaluate support for both the proposed benefits of soy and concerns and identify areas where more research is needed. ------------------ Aufgenommen beim VegMed 2014 --