Soy Isoflavones Improve Postmenopausal Immune Function

Soy isoflavones were found to modulate immune function in healthy postmenopausal women according to a new placebo controlled trial published in the American Journal of Clinical Nutrition (83, 5:1118-25, 2006). Researchers from Washington State University hypothesized that women's immune systems may become compromised after menopause due to the effects, in aging, of diminishing concentrations of estrogen, an immune-modulating hormone. Soy Isoflavones, known for their estrogenic and antioxidant properties, were thought to offer potential immunologic benefit to women during this stage of life.

Researchers randomly assigned 52 postmenopausal women ages 50 to 65 years to one of three study groups. A soymilk group received 71.6 mg of isoflavones derived from 706 milliliters of soymilk per day, plus a placebo supplement. A supplement group received 70 mg of isoflavones in a supplement plus 706 milliliters per day of cow's milk. A control group received 706 milliliters of cow's milk per day plus a placebo supplement. Plasma and 24-hour urine samples were obtained at baseline and at 16 weeks and assayed for immune variables including lymphocytes, cytokine production and markers of inflammation and oxidative damage. Isoflavone supplementation resulted in higher B cell populations and lower plasma concentrations of 8-hydroxy-2-deoxy-guanosine, an oxidative marker of DNA damage. Researchers concluded that soymilk and supplemental isoflavones modulate B cell populations and appear to be protective against DNA damage in postmenopausal women.

Soy isoflavones are a class of phytoestrogens, plant compounds similar to estrogen, which are capable of binding and modulating cellular estrogen receptor cites. Soy isoflavones may exert a hormone normalizing effect in pre and postmenopausal women. Its action is determined by a woman's endogenous estrogen levels. In the presence of excessive estrogen (e.g. PMS), isoflavones exercise an antiestrogenic effect by competing with estrogen for receptor cites. Conversely, as estrogen levels decline in menopause, isoflavones provide a mild estrogenic activity. The hormone modulating effects of soy isoflavones may be beneficial in menopause, endometriosis, cervical dysplasia, menstrual irregularities, and breast cancer prevention.

Soy isoflavones may inhibit or even reverse osteoporotic changes in menopausal women. Isoflavones are thought to help preserve bone density by a direct estrogenic action on osteoblastic cells, but may also aid by reducing osteoclastic activity. A number of studies, clinical and epidemiological, indicate that soy isoflavones may reduce risk of a number of types of cancer including hormone dependant cancers (breast and prostate) as well as certain other cancers including colon, lung and leukemia. Several mechanisms have been suggested including inhibition of tumor promoting enzymes and inhibition of tumor angiogenesis. The substitution of soy for animal protein has long been accepted as a dietary strategy for hypercholesterolemia and heart disease. More recently the soy isoflavone genistein has been found to play an important role in inhibiting platelet activation, thrombin formation and smooth muscle cell proliferation, which lead to the formation of atherosclerotic plaque.

Bio-Design Soy Isoflavones provides 40 mg of isoflavones per capsule. (Whole soy foods such as tofu and soymilk contain approximately 35 to 40 mg of soy isoflavones per 1/2 cup serving.) Bio-Design Soy Isoflavones also provides naturally occurring soy saponins and other soy trace nutrients. Taking one capsule twice daily as a dietary supplement provides a significant soy component to the diet.