Beneficial Effects of Soy Phytoestrogen Intake in Postmenopausal Women With Type 2 Diabetes

Abstract

OBJECTIVE—Phytoestrogen consumption has been shown to reduce risk factors for cardiovascular disease. Type 2 diabetes confers an adverse cardiovascular risk profile particularly in women after menopause. The aim of this study was to determine whether a dietary supplement with soy protein and isoflavones affected insulin resistance, glycemic control, and cardiovascular risk markers in postmenopausal women with type 2 diabetes. RESEARCH DESIGN AND METHODS—A total of 32 postmenopausal women with diet-controlled type 2 diabetes completed a randomized, double blind, cross-over trial of dietary supplementation with phytoestrogens (soy protein 30 g/day, isoflavones 132 mg/day) versus placebo (cellulose 30 g/day) for 12 weeks, separated by a 2-week washout period. RESULTS—Compliance with the dietary supplementation was >90% for both treatment phases. When compared with the mean percentage change from baseline seen after 12 weeks of placebo, phytoestrogen supplementation demonstrated significantly lower mean values for fasting insulin (mean ± SD 8.09 ± 21.9%, P = 0.006), insulin resistance (6.47 ± 27.7%, P = 0.003), HbA1c (0.64 ± 3.19%, P = 0.048), total cholesterol (4.07 ± 8.13%, P = 0.004), LDL cholesterol (7.09 ± 12.7%, P = 0.001), cholesterol/HDL cholesterol ratio (3.89 ± 11.7%, P = 0.015), and free thyroxine (2.50 ± 8.47%, P = 0.004). No significant change occurred in HDL cholesterol, triglycerides, weight, blood pressure, creatinine, dehydroepiandrosterone sulfate, androstenedione, and the hypothalamic-pituitary-ovarian axis hormones. CONCLUSIONS—These results show that dietary supplementation with soy phytoestrogens favorably alters insulin resistance, glycemic control, and serum lipoproteins in postmenopausal women with type 2 diabetes, thereby improving their cardiovascular risk profile.