Soy isoflavones: Are they useful in menopause?

In October 1999, the US Food and Drug Administration authorized the use on food labels of health claims associated with soy protein and the reduced ri sk of coronary heart disease, Several studies have indicated that a total d aily intake of 25 g of soy protein paired with a low-fat diet resulted in c linically important reductions of total cholesterol and low-density lipopro tein (LDL) cholesterol levels, Soybeans are a rich source of isoflavones, a class of phytoestrogens found predominantly in legumes and beans, Soy isof lavones are heterocyclic phenols with structural similarity to estradiol-17 beta and selective estrogen receptor modulators, Actions at the cellular l evel depend on the target tissue, receptor status of the tissue, and the le vel of endogenous estrogen, Studies of soy-based diets evaluating the relat ion between soy consumption and serum lipid concentrations revealed that so y consumption significantly decreased total cholesterol, LDL cholesterol, a nd triglyceride levels, However, the soy isoflavones do not increase high-d ensity lipoprotein cholesterol or triglyceride levels, The effects of soy p rotein on other target tissues reflect estrogenlike agonist and antagonist effects. Epidemiological studies suggest a protective effect of soy protein on breast tissue as evidenced by the lower rates of breast cancer in East Asian countries where soy is a predominant part of the diet. Data available from human studies on the effect of isoflavones on osteoporosis are limite d, and additional studies are needed to support a role in osteoporosis prev ention. Thus far, there is no evidence for a stimulatory effect of isoflavo nes on the endometrium. A few studies reveal a minimal effect of soy on hot flashes, with soy reducing hot flashes 45% and placebo causing a 30% reduc tion compared with an approximate 70% reduction in hot flashes with estroge n replacement therapy. Evidence from laboratory studies reveals neither a p ositive nor a negative effect of soy isoflavones on cognition. To date, no adverse effects of short- or long-term use of soy proteins are known in hum ans. The only adverse effects known are those reported in animals (infertil ity in sheep and quails grazing on phytoestrogen-rich pastures). In conclus ion, soy isoflavones are biologically active compounds, Current data are in sufficient to draw definitive conclusions regarding the use of isoflavones as an alternative to estrogen for hormone replacement in postmenopausal wom en. Although epidemiological and basic: laboratory studies allude to the po ssible protective effects of soy isoflavones at specific target tissues, ra ndomized, placebo-controlled clinical trials are necessary to address these important issues.