Kill two birds with one stone: soy boosts bone and insulin

Kill two birds with one stone: soy boosts bone and insulin By Stephen Daniells

3/3/2008- Supplements of soy isoflavones may lead to improvements in bone health and blood sugar metabolism, according to new research from Japan. The results of the study, published in the journal Geriatrics & Gerontology International, supports the benefits of soy isoflavones in the aglycone form against osteoporosis and diabetes. The study adds to the ongoing debate about the efficacy of soy isoflavones and bone health, with previous studies having reported conflicting results. Earlier studies from China have linked soy isoflavones to increases in bone mineral density (BMD), while a recent large study in the Archives of Internal Medicine (2005, Vol. 165, pp. 1890-1895) reported that high soy consumption was linked with a 48 per cent decrease in fractures for women who had been menopausal for less than 10 years. "Our results suggest that 4-week intake of fermented soybean soup containing 24 mg of isoflavone aglycone improves bone metabolism by inhibiting the excessive enhancement of bone resorption and promoting bone formation in post-menopausal women," wrote lead author Mari Mori from Mukogawa Women's University Institute for World Health Development. "This intervention study was conducted under other soybean-based food restriction. In the present Japanese society, in which traditional soybean product intakes are decreasing, the continuous dietary intake of fermented soybeans may reduce the risks of osteoporosis, metabolic syndrome and diabetes." The new randomized, test diet-placebo, independent parallel double-blind study involved 56 healthy post-menopausal women aged between 47 and 70. The women were randomly assigned to receive an aglycone-rich fermented soybean soup, providing a daily isoflavone aglycone dose of 24 milligrams, or placebo soup for weeks. The subjects did not eat any other soybean-based foods and isoflavone supplements for five week prior to the start and for the duration of the study. It has been reported that the aglycone form of isoflavones is more bioavailable since they are smaller molecules and are more hydrophobic, and so do not dissolve as easily in water and thus rapidly excreted. Key findings Mori and co-workers report that isoflavone levels significantly increase in the urine after four weeks of supplementation, compared to placebo. These increase occurred in combination with an increase in the excretion of deoxypyridinoline, a marker of bone resorption (weakening). Moreover, levels of osteocalcin, a marker of bone formation (strengthening) were significantly increased after four weeks, they added. "Those results indicate that four-week intake of fermented soybeans improves bone metabolism in post-menopausal women by attenuating the excessive enhancement of bone resorption as well as by promoting bone formation," wrote the researchers. "In this study, we did not measure bone mineral density, as the ingestion period was relatively short. However, such a daily intake of fermented soybean, if continued, is expected to improve bone metabolism and to contribute to the primary prevention of osteoporosis," they added. The researcher also add that blood levels of insulin were significantly lower after four weeks of supplementation, compared to placebo, while blood sugar (glucose) levels were similar between the groups. "These results suggest that four-week intake of fermented soybeans improves insulin resistance in post-menopausal women whose isoflavone intake was restricted," they stated. Isoflavones are well known phytoestrogens - active substances derived from plants that have a weak estrogen-like action. In addition to their potential benefits for heart and bone health in post-menopausal women, the compounds 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. Source: Geriatrics & Gerontology International Volume 8, Supplement 1, Pages S8-S15, doi:10.1111/j.1447-0594.2007.00399.x "Isoflavones as Putative Anti-aging Food Factors in Asia and Effects of Isoflavone Aglycone-rich Fermented Soybeans on Bone and Glucose Metabolisms in Post-menopausal Women" Authors: M. Mori, Y. Okabe, H. Tanimoto, T. Shimazu, H. Mori, Y. Yamori