Genistein increased BMD in postmenopausal women

Two years of daily treatment with the isoflavone phytoestrogen genistein increases bone mineral density (BMD) at the anteroposterior lumbar spine and femoral neck in osteopenic postmenopausal women, according to a randomized, double-blind trial involving almost 400 women.

After a 4-week stabilization period, during which the women adhered to a low-soy, reduced-fat diet, they received either placebo or 54 mg of genistein daily for 2 years, an amount similar to that found in vegetarian Asian diets.

After the 2 years, the women receiving genistein had increased BMD at the anteroposterior lumbar spine (change, 0.049 g/cm² ; 95% CI, 0.035–0.059) and femoral neck (change, 0.035 g/cm² ; CI, 0.025–0.042), while those in the placebo group lost BMD at both locations (spine, –0.053 g/cm² ; CI, –0.058 to –0.035) (femoral neck, –0.037 g/cm² ; CI, –0.044 to –0.027). The difference for the spine was 0.10 g/cm² (CI, 0.08–0.12; P<0.001) and for the femoral neck: 0.062 g/cm² (CI, 0.049–0.073; P<0.001).

The authors noted that caution is needed when administering genistein to women at high risk for endometrial and/or breast cancer, and that further study is needed to determine whether genistein's effects translate into a reduced fracture risk and whether it is useful for other types of bone loss, such as glucocorticoid-induced osteoporosis.

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