Soy and Postmenopausal Women.




Am J Clin Nutr

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Scientists classify soy isoflavones from the plant Glycine max as phytoestrogens. Phyto is a Greek root word meaning plant, so phytoestrogens are plant-based compounds that have estrogen-like activity. Because they are structurally similar to estrogens, isoflavones exert weak estrogenic activity. Because of their estrogen-like effects, isoflavones have been studied for a wide spectrum of health benefits.

Soybeans and soy foods like tofu are the best dietary source of isoflavones. However, many soy protein concentrates and soy products processed with alcohol may not contain isoflavones. A synthetically derived form of isoflavones, known as ipriflavone, is also available.

A recent study examined the role of soy isoflavones on immune function and DNA damage in postmenopausal women. Due to decreased estrogen levels, postmenopausal women may be prone to more infections as the body cannot fight off infection as it previously could. This study involved using both soy milk and soy dietary supplements. This study involved 52 postmenopausal women. These participants received one of the following three treatments, 1. cow’s milk with a placebo pill, 2. soy milk with a placebo pill, or 3. a soy isoflavone supplement with cow’s milk. The authors measured markers of DNA damage and of immune function after this 16-week trial. The results showed that women with an isoflavone intake had higher B-cell populations. In addition, those with an intake of isoflavones also had reduced levels of a chemical component, which is present during DNA damage. The authors concluded that, “Soymilk and supplemental isoflavones modulate B cell populations and appear to be protective against DNA damage in postmenopausal women.”1


1. Ryan-Borchers TA, et al. Soy isoflavones modulate immune function in healthy postmenopausal women. Am J Clin Nutr. May 2006;83(5):1118-1125.