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Phytoestrogen Intake Prevents Bone lossThis randomized, double-blind, placebo-controlled trial was conducted at three medical centers in Italy. The trial studied the effects of 54mg/day of pure soy genestein on bone metabolism in postmenopausal women with osteopenia. Bone density at the femoral neck and lumbar spine was tested after 24 months along with serum levels of bone-specific alkaline phosphatase, markers of bone turnover (urinary excretion of pyridinoline and deoxypyridinoline), insulin-like growth factor 1 (IFG-1) and endometrial thickness.

389 postmenopausal women aged 49 to 67 with a femoral neck bone mineral density (BMD) of less than 0.795 g/cm2 received either genistein or placebo. All women received calcium and vitamin D. After 2 years, BMD at the femoral neck increased in the group that received the genistein and declined in the women who received placebo. A mean change of 0.035 gm/cm2 for genistein vs – 0.037 gm/cm2 for placebo. A smaller positive change was seen at the lumbar spine for genistein and a smaller loss in the placebo group.

Bone turnover decreased significantly in the women who received genistein, and bone-specific alkaline phosphatase and IGF-1 also significantly increased. None of these markers changed in the placebo group. Genistein did not significantly change the endometrial thickness but did reduce the mean number of hot flashes. Side effects included gastrointestinal symptoms and the withdrawal rate from the study due to these side effects was 19% in the genistein group vs 8% in the placebo group.

Marini H, Minutoli L, Polito F, et al. Effects of phytoestrogen genistein on bone metabolism in osteoenic postmenopausal women: a randomized trial. Ann Intern Med 2007;146:839-847.

Comments: Previous studies have reported that women with high soy diets had a lower risk for osteoporosis. The current report provides additional compelling evidence that 54 mg of genistein per day, along with 500 mg of calcium and vitamin D 400 IU for 2 years can increase the BMD of the lumbar spine and femoral neck. Further evidence is provided by the decreased urinary markers for bone resorption and the increase in circulating levels of the bone formation markers.

More than twice as many women had side effects in the genistein group and discontinued treatment because of these symptoms. That said, these side effects are considerably less than those reported for many women who utilize bisphosphanates for bone loss. Although I would not consider genistein an adequate treatment for women with osteoporosis, I would consider genistein an important treatment in women with osteopenia, especially up to the age of 65, prior to higher age related risks for fracture.

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