Isoflavones improve cardiovascular profile in obese, older women

Obese postmenopausal women who supplement their diet with 70 mg/d isoflavones (daidzein, glycitein, and genistein, as well as their parent source, soybeans) in addition to exercising regularly enjoy significantly greater cardiovascular benefits than that provided by exercise alone, according to the results of randomized, double-blind study.

Canadian researchers randomized 50 healthy but obese postmenopausal women to receive either isoflavone supplements or placebo; both groups participated in an exercise program three times per week.

Compared to the group who merely exercised, those who exercised and took isoflavones had significantly greater positive effects on body weight, total and abdominal fat mass, body mass index, appendicular fat-free mass, fat-free mass/fat mass ratio, and sex hormone-binding globulin.

The author of an accompanying editorial points out that the safety and efficacy of isoflavone supplements still need to "be evaluated in larger clinical trials with adequate power to clearly detect both benefits and risks." Because they work at least partially via estrogen receptors, their effects, particularly in the presence of estrogen-sensitive malignancies, remain a concern.

Until such questions are answered, the author of the editorial recommends we tell patients to follow the advice of the American Heart Association (AHA), which is to enjoy soy food products (e.g., tofu, soy butter, soy nuts, soy burgers, soy beans) that are high in polyunsaturated fats, fiber, vitamins, and minerals and low in saturated fat, but to "skip the supplements for now."

Aubertin-Leheudre M, Lord C, Khalil A, et al. Effect of 6 months of exercise and isoflavone supplementation on clinical cardiovascular risk factors in obese postmenopausal women: a randomized, double-blind study. Menopause. 2007;14:624-629.

Stuenkel CA. Isoflavones and cardiovascular risk in postmenopausal women: no free lunch. Menopause. 2007;14:606-608.