Effects of high-dose isoflavones on metabolic and inflammatory markers in healthy postmenopausal women

Abstract

After menopause, women experience changes in body composition, especially an increase in fat mass. In addition, advancing age, decreased physical activity, and increased inflammation may predispose them to develop type 2 diabetes. Isoflavones have been shown to improve metabolic parameters in postmenopausal women. However, the effect of isoflavones on adipokines/cytokines remains unclear. The purpose of this study was to evaluate the effect of high-dose isoflavones on inflammatory and metabolic markers in postmenopausal women. We measured glucose, insulin, and adipokines/cytokines in 75 healthy postmenopausal women who were randomized to receive 20 g of soy protein with 160 mg of total isoflavones (64 mg genistein, 63 mg daidzein, and 34 mg glycitein) or 20 g of soy protein placebo for 12 weeks. Women taking estrogen discontinued therapy at least 3 months before the study. The supplements were given in a powder form and consumed once daily with milk or other beverages. Mean ages in the placebo and active groups were similar (P = 0.4). Average time since menopause was 9 years, and two thirds of the women underwent natural menopause. There was no significant difference in body mass index at baseline between the groups (placebo, 25.1 kg/m; active, 26 kg/m) and it did not change significantly during the study. At baseline, the placebo group had significantly higher levels of tumor necrosis factor alpha (P < 0.0001); otherwise, there was no difference in any other parameter. After 12 weeks of treatment, there were significant positive changes in tumor necrosis factor alpha levels within the placebo group (P < 0.0001) and adiponectin levels within the isoflavone group (P = 0.03). Comparison of pre-post change between the groups showed a small but significant increase in serum adiponectin levels in the isoflavone group (P = 0.03) compared with the placebo group. No significant changes were seen in any other parameter between the two groups. Healthy, normal-weight postmenopausal women may not experience improvement in metabolic parameters when given high-dose isoflavones despite an increase in serum adiponectin levels. The role of isoflavones in obese and insulin-resistant postmenopausal women needs exploration.