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So say Italian researchers including Francesco Squadrito, MD, of Italy's University of Messina.
First, the women got DEXA (dual X-ray absorptiometry) bone mineral density scans of their upper thigh bone (femoral neck) and lower (lumbar) spine. Next, they followed a low-fat, healthy diet for a month. Then the researchers split the women into two groups.
The other group received similar pills without genistein (placebo). The women took their pills daily for two years without knowing if the tablets contained genistein.
During that time, the women got annual DEXA scans of their femoral neck and lumbar spine. They were evaluated every three months for problems including breast tenderness, hot flashes, depression, gastrointestinal symptoms, irritability, insomnia, and vaginal bleeding.
Better Bone Density
After two years, the DEXA scans showed increases in bone mineral density in women taking genistein.
Bone mineral density dropped during the same period in women taking the placebo pills.
The researchers didn't gather information on fractures, so they're not sure if genistein's effects mean fewer fractured or broken bones.
Genistein's chemical structure resembles estrogen, the female sex hormone that protects bones and fades after menopause, the researchers note in the Annals of Internal Medicine.
Because of those estrogen-like properties, "caution is needed when administering genistein, especially in patients at high risk for endometrial or breast cancer," write Squadrito and colleagues.
However, the study shows that the uterus lining (endometrium) wasn't thicker in women taking genistein than in those taking the placebo.
Gastrointestinal side effects caused 37 women taking genistein and 15 taking the placebo to quit the study.
Based on the results, Squadrito's team calls for studies testing genistein against osteoporosis.
SOURCES: Marini, H. Annals of Internal Medicine, June 19, 2007; vol 146: pp 839-847. News release, American College of Physicians.
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