Soy and Lipoproteins in Postmenopausal Women

To determine the effects of soy on lipids, lipoproteins and lipoprotein subclass in a sample of African-American and white postmenopausal women with low-density lipoprotein (LDL) cholesterol elevations that may increase their lifetime risk for cardiovascular disease but would not qualify for definite pharmacotherapy under current guidelines.

BACKGROUND: Cardiovascular disease (CVD) remains the leading cause of mortality and disability in postmenopausal women. Menopause alters serum lipids and lipoproteins to produce a more atherogenic lipid profile that may contribute significantly to the increased risk for the development of CVD over the lifetime of women. Clinical trials have demonstrated a beneficial effect of soy protein containing isoflavones (soy) on plasma lipids and lipoproteins; however, these studies included small numbers of postmenopausal women and virtually none included sufficient African-American women. In addition, no published data existed in 2001 on the impact of soy on atherogenic lipoprotein subclasses in postmenopausal women. DESIGN NARRATIVE: The study was a double blind, parallel group, randomized clinical trial. A total of 216 healthy postmenopausal women (50 percent African-American) with LDL cholesterol between 130 mg/dL and 190 mg/dL were enrolled. Following a pre-randomization run-in period on a NCEP Step I diet, women were randomized to receive soy containing isoflavones or casein dietary supplements for 3 months. Major outcome variables were assessed in both groups at baseline and again at 3 months. It was hypothesized that soy supplementation would result in significantly greater reduction in LDL cholesterol, LDL particle concentration, and prevalence of dense LDL particles and improvement in menopausal quality of life compared with placebo and that these effects would be comparable in African-Americans and whites. This was the first study to determine whether a natural plant product could ameliorate the unfavorable changes in known and novel lipid risk factors that are a consequence of menopause in both African-American and white women. The unique transitional outcomes explored in this study added substantially to the limited body of knowledge of the effects of soy. Evaluation of this nutritional alternative to hormone replacement therapy (HRT) that may provide a beneficial effect on lipid risk factors and menopausal symptoms but would be free of the adverse effects on triglycerides, the breast and uterus, and thrombotic events associated with HRT could have significant public health implications for postmenopausal women.