Evidence Mounts for Soy's Menopause Benefits
Lee Swanson Research Update
May 2009
Soy isoflavones in the aglycone form may reduce cholesterol, improve antioxidative properties of the liver and prevent degeneration, according to a new study with rats.
The study, published in the online open-access journal Nutrition & Metabolism, adds to previous science about the benefits of soy isoflavones for reducing the symptoms of menopause.
"These ovariectomized animals are a good model for study of the menopause as the loss of estrogen from the ovaries mimics the natural reduction in estrogen seen in menopausal women," explained lead researcher Robin Chiou from the national Chiayl University in Taiwan.
"SAI (soy aglycons of isoflavone) itself has weak estrogenic properties and we’ve shown here that menopause-related syndromes can be prevented or improved by dietary supplementation with the compounds it contains," he added.
Isoflavones are well-known phytoestrogens—active substances derived from plants that have a weak estrogen-like action. Isoflavones from soy have been shown to provide a number of health benefits, including the promotion of heart health and the maintenance of bone health in post-menopausal women.
Soy isoflavones have also been studied for their role in cancer prevention and slowing down the ageing process in peri-menopausal women, and have proved to be a popular alternative to hormone replacement therapy for those wishing to control menopause symptoms without resorting to drugs.
Thirty ovariectomized Sprague-Dawley rats were distributed into three groups: control group; a low SAI group (0.0135% SAI in the diet, equivalent to 80 mg per day for a 60 kg human) and a high dose SAI group (0.027% SAI). Ten other rats acted as the negative controls and did not have their ovaries removed.
The soybean supplement contained 80% soy bean flour, 4.5% daidzein, 14.5% genistein and about 1.0% other isoflavones.
After three months, the researchers found that the ovariectomized animals gained more weight than the negative control animals. Animals fed the soy isoflavones had higher blood levels of isoflavones, said the researchers, and significantly lower LDL cholesterol levels and higher HDL cholesterol levels.
"It is generally agreed that the higher HDL and the lower LDL concentrations are of benefit in chemoprevention of cardiovascular diseases. Our findings support the indication that soybean consumption may prevent coronary heart disease," said Chiou.
Furthermore, liver antioxidative activities were increased, as evidenced by decreased values of TBARS (thiobarbituric acid-reactive substance). Finally, the decline in the lining of the vagina observed for the ovariectomized group was "noticeably improved by dietary supplementation with SAI," said the researchers.
"The observations that dietary SAI supplementation in performance of estrogenic effectiveness in improvement of serum biochemical attributes, enhancement of liver antioxidative capacities and protection of vaginal epithelium are of importance from the viewpoint of healthcare and development of dietary supplements," wrote the researchers.
"Apparently, diets supplemented with soy aglycons of isoflavone have conferred health benefits to the ovariectomized rats. This further supports the effectiveness that menopausal-related syndromes could be prevented or improved by dietary supplementation with any aglycons of isoflavone," the researchers concluded.
Nutrition & Metabolism Published online.
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