ObjectiveTo investigate the effect of soy protein supplementation with known levels of phyto-estrogens on cardiovascular disease risk factors and menopausal symptoms in perimenopausal women.MethodsA randomized, double-blind crossover trial was conducted in 51 women consuming isocaloric supplements containing 20 g of complex carbohydrates (comparison diet), 20 g of soy protein containing 34 mg of phytoestrogens given in a single dose, and 20 g of soy protein containing 34 mg of phytoestrogens split into two doses. Women were randomly assigned to one of the three diets for 6-week periods and subsequently were randomized to the remaining two interventions to determine whether differences existed between the treatment diets for cardiovascular disease risk factors, menopausal symptoms, adherence, and potential adverse effects.ResultsSignificant declines in total cholesterol (6% lower) and low density lipoprotein cholesterol (7% lower) were observed in both soy diets compared with the carbohydrate placebo diet. A significant decline in diastolic blood pressure (5 mm Hg lower) was noted in the twice-daily soy diet, compared with the placebo diet. Although nonsignificant effects were noted for a number of measures of quality of life, a significant improvement was observed for the severity of vasomotor symptoms and for hypo-estrogenic symptoms in the twice-daily group compared with the placebo group. No significant effects were noted for triglycerides, high density lipoprotein cholesterol or frequency of menopausal symptoms. Adherence was excellent in all groups.ConclusionsSoy supplementation in the diet of nonhypercholesterolemic, nonhypertensive, perimenopausal women resulted in significant improvements in lipid and lipoprotein levels, blood pressure, and perceived severity of vasomotor symptoms. These data corroborate the potential importance of soy supplementation in reducing chronic disease risk in Western populations.