Plasma lipoproteins in soy-treated postmenopausal women: a double-blind, placebo-controlled trial.

BACKGROUND AND AIM: Postmenopausal modification of the lipid profile plays a major role in the risk of ischemic heart disease. Lifestyle counseling and estrogen replacement therapy have all been proposed as first-line measures, but there is no agreement on the best way to treat climacteric dyslipidemia. Soybean-based diet seems particularly attractive in this context, given its cholesterol lowering potential, its hypothetical anticancerous effects and possible modification of climacteric symptoms.

METHODS AND RESULTS: We evaluated the effect of 60 g isolated soy protein (ISP) daily on the lipid profile of 104 postmenopausal women (53.3 +/- 3.3 years) in a double-blind, parallel, placebo-controlled (caseinate) trial, as part of a broader assessment of the effect of ISP on climacteric symptomatology. Serum total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, apo A-I, apo B and lipoprotein (a) were determined before and after a 12-week diet modification. Seventy-seven women completed the trial. Both soy and placebo determined a significant reduction in total cholesterol (-0.42 +/- 0.79 and -0.40 +/- 0.57 mmol/L) and LDL-cholesterol (-0.35 +/- 0.72 and -0.31 +/- 0.54 mmol/L), but only soy had a significant lowering effect on apo B and the LDL-cholesterol/HDL-cholesterol ratio (-6% and -8% from baseline respectively); lipoprotein (a) plasma levels were not significantly changed by either treatment. Forty-four women were dyslipidemic at baseline; those with increased LDL concentrations showed a somewhat greater improvement in their lipoprotein profile (LDL-cholesterol and apo B reduction) with soy rather than placebo. No further information emerged when the subjects were divided into three apo E phenotypes.

CONCLUSIONS: We conclude that diet supplementation with 60 g ISP is slightly better than caseinate in favorably modifying the lipoprotein metabolism of postmenopausal women; this effect is more evident in hypercholesterolemic subjects.