A diet rich in soy may help women retain strong bones after menopause, thereby reducing their risk of fractures and osteoporosis, research findings suggest.

In a study published in the January issue of Obstetrics and Gynaecology, researchers report that postmenopausal women who consumed the most soy-based foods had the strongest bones after adjusting for the number of years since menopause began, and their weight. Very thin postmenopausal women tend to have frail bones.

Some studies have suggested that plant estrogens in soy, known as phytoestrogens, can alleviate some of the symptoms of menopause. In particular, compounds known as isoflavones, which have a chemical structure similar to the female estrogen hormone estradiol, are thought to mimic the effects of natural estrogen.

This may be helpful during menopause when estrogen production drops. Lower estrogen levels can increase the risk of fractures and the bone-thinning disease osteoporosis, and lead to other menopausal symptoms such as hot flashes, irritability, aching joints and depression, the authors note.

To investigate, the team of Japanese researchers led by Dr. Yoshiaki Somekawa estimated the intake of isoflavones in the diets of 478 postmenopausal Japanese women. Overall, heavier women and those who recently went through menopause had the thickest bones.

In both the early and late postmenopausal periods, women who consumed the highest level of isoflavones in foods such as tofu, boiled soybeans and soy milk, had significantly thicker bones than women who consumed the lowest level of isoflavones.

Women who consumed the greatest amount of isoflavones in the early postmenopausal period also had significantly fewer backaches and aching joints. But intake of isoflavones did not appear to influence menopausal symptoms in late postmenopause, the report indicates.

"High consumption of soy products is associated with increased bone mass in postmenopausal women and might be useful for preventing (low estrogen) effects," the authors conclude.

© Reuters Limited 2001.