Supplements containing soy isoflavones do little to preserve women's bone mass after menopause, according to new research published in the November 2009 issue of the American Journal of Clinical Nutrition.
Isoflavones are natural chemicals found in soybeans and certain other plant foods that are structurally similar to estrogen. They appear to have estrogen-like effects in the body and, since declining estrogen levels after menopause encourage bone loss, it's thought that soy isoflavone supplements may protect women's bone mass in their later years.
In this study, 255 postmenopausal women were randomly assigned to one of three groups: one that took 80 milligrams (mg) of a soy isoflavone supplement each day; one that took a 120-mg dose; and one given inactive placebo pills. All of the women also took calcium and vitamin D supplements.
Over three years, women in the soy isoflavone and placebo groups showed similar whole-body loss of bone mass, as well as bone density in the spine and hip area.
These findings add to a conflicting research on soy and postmenopausal bone health. Previous studies have suggested that soy-based foods, isolated soy protein or isoflavone-containing supplements may be beneficial, while others have found no positive effects.
Loss of bone mass and bone density can lead to osteoporosis, or "porous bones", a condition which increases risk of hip, wrist and spine fractures. According to Osteoporosis Canada, over 2 million Canadian men and women are living with this condition.
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