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.