The animal 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 the menopause.
"These ovariectomised animals are a good model for study of the menopause as the loss of oestrogen from the ovaries mimics the natural reduction in oestrogen seen in menopausal women,” explained lead researcher Robin Chiou from the National Chiayi University in Taiwan.
“SAI (soy aglycons of isoflavone) itself has weak oestrogenic 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 oestrogen-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.
They 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.
Study details
The researchers divided 30 ovariectomised Sprague-Dawley rats were distributed into three groups: control group; a low SAI group (0.0135 per cent SAI in the diet, equivalent to 80 mg per day for a 60 kg-human), and a high dose SAI group (0.027 per cent SAI). A further 10 rats acted as the negative controls and did not have their ovaries removed.
The soybean supplement contained 80 per cent soy bean flour, 4.5 per cent daidzein, 14.5 per cent genistein, and about 1.0 per cent other isoflavones, (Glory Biotech Co., Taiwan).
After three months, the researchers found that the ovariectomised 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 ovariectomised control group was “noticeably improved by dietary supplementation with SAI”, said the researchers.
Importance for supplements
“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 ovariectomised rats. This further supports the effectiveness that menopausal-related syndromes could be prevented or improved by dietary supplementation with soy aglycons of isoflavone,” they concluded.
Source: Nutrition & Metabolism 2009, 6 http://www.nutritionandmetabolism.com“Supplementary health benefits of soy aglycons of isoflavone by improvement of serum biochemical attributes, enhancement of liver antioxidative capacities and protection of vaginal epithelium of ovariectomized rats” Authors: T.-F. Lien, Y.-L. Hsu, D.-Y. Lo, R.Y.-Y. Chiou