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Introduction Health concerns surrounding menopause mainly relate to the decrease in circulating estrogens that result from follicular depletion of ovaries. With increasing life expectancy, a woman spends over one third of her life span in postmenopausal years. Hence disease like ischemic heart disease, osteoporosis, Alzheimer disease and cancers are becomes major health concerns. Estrogen Replacement Therapy is effective for climatic symptoms and has been proposed to help many of the chronic health disease with improved quality of life. However, only 35-40% of post-menopausal women ever begin ERT and less than 15% continue taking for a long time either because fears of breast cancer or due to the side effects of accompanying progestin therapy. Hence, a therapy, which would protect against coronary artery disease and reduce incidence of osteoporosis related complications, is required to reap maximum long-term benefits. The potential for other sources of estrogen e.g. plant estrogens referred to as phyto-estrogens or isoflavones, has received a great deal of attention as a way to treat and manage the symptoms of menopause. Because of nutritional approach rather than pharmacological approach, compliance may be improved. Many types of phyto-estrogens have been described, including cousmestans, lignans and isoflavones. The isoflavones genistein and daidzein are the best researched phyto-estrogens and are found in soya products. These readily bind to estradiol receptors. The potential benefits of phyto-estrogens may be related to their preferential binding and activity at these two types receptors. The phyto=estrogens also seem to possess agonist and antagonist properties resembling selective estrogen receptor modulators. These unique properties may be responsible for some of the clinical benefits observed with phyto-estrogens. In the last few years many studies have been conducted on the potential role of soya protein and phyto-estrogens for the management of post-menopausal women. Soya and Vasomotor Symptoms Few clinical trials have been conducted evaluating the role of phyto-estrogens in relieving hot flashes associated with menopause. Most randomized double blind and placebo-controlled trials indicate favourable reduction in the duration, frequency and severity of hot flashes, where as others do not. Many of these trials used an isoflavones intake between 34 mg and 75 mg daily. One double blind, placebo controlled trial evaluated the role of only soya phyto-estrogens in 149 breast cancer survivors. At the end of 9 weeks, there were no differences in foot flushes between study and control group. It is unknown if soya proteins other than the isoflavones are responsible for controlling hot flushes, because this trial used only an isoflavones tablet formulation, the role of other potential soya ingredients remains unknown. Soya and Cardiovascular health Many randomized, controlled, clinical trial have been conducted evaluating the effects of soya proteins and isoflavones on plasma lipids and lipoproteins. Epidemiological and cross-cultural studies and numerous animal support the notion that soya consumption is cardio-protective. The most notable study, a meta-analysis of randomized, double blind, placebo controlled trials reported significant improvements in low-density lipoprotein cholesterol and tri-glycerides without affecting high-density lipoprotein cholesterol values. The result of the meta-analysis suggest that, on average, 25 gm of soya protein daily can reduce cholesterol by 10%. This evidence served as the basis for the US FDA’s approval for Soya Protein and Coronary Heart disease.
Crouse et al evaluated the effects of soya protein supplement containing
various levels of isoflavones on plasma lipids and lipoproteins
concentrations and compared with a casein supplement. Soya protein
containing 62 mg of isoflavones significantly reduced total and LDL
cholesterols. In addition, isoflavones concentration had a dose response
effect on lowering LDL cholesterol.
Osteoporosis and resulting fractures are a major cause of disability in
postmenopausal women. Hormone replacement therapy can increase vertebral
bone mineral density by 3.5-% in postmenopausal women. The phyto-estrogens
may also provide some protective effects on vertebral and radial bone
mineral density. There are five randomized, double blind placebo
controlled clinical trials in women that have reported on the effects of
soya/ isoflavones supplementation on bone density. Three of these
studies reported positive effects in postmenopausal women and in
general, these effects are only seen at isoflavones consumption of 60mg
per day. Soya Effect on Breast Cancer and Endometrial Cancer risk The HRT associated risk of breast cancer is between 1.2 and 1.4, on the length of treatment. In addition the role of progestins must be considered. Recent analysis of the Breast Cancer Detection and Demonstration Project indicate that the addition of a progestin to protect the endometrial cells proliferation to the same degree as mammalian estrogens. In fact, soya phyto-estrogens appear to be estrogen antagonists at some does. Animal studies and human epidemiological studies indicate breast cancer protective effect of soya proteins. Although soya phyto-estrogens have been implicated in overt uterotropic effect in rats, no such effect has been in women and non- human primates. There is only one case control study of dietary soya intake and endometrial cancer risk, which showed an approximately 50% reduction in endometrial cancer risk between the lowest and highest quantities of soya intake. Conclusions
In summary, soya protein and isoflavones appear to have a promising role
in the management of menopausal symptoms and associated disease. There
is emerging evidence from a few clinical studies that phyto-estrogens
can reduce the risk of heart disease and osteoporosis. But the evidence
is limited and literature review provides contradictory reports.
Therefore further placebo-controlled studies are required. If these
effects are proved, a nutritional supplement derived from a natural
product may be more acceptable than a pharmacological approach to a
physiological state in a woman’s life and thus improve compliance. |
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