Effects of moderate alcohol intake on fasting insulin and glucose concentrations and insulin sensitivity in postmenopausal women: a randomized controlled trial

CONTEXT: Epidemiologic data demonstrate that moderate alcohol intake is associated with improved insulin sensitivity in nondiabetic individuals. No controlled-diet studies have addressed the effects of daily moderate alcohol consumption on fasting insulin and glucose concentrations and insulin sensitivity. OBJECTIVE: To determine whether daily consumption of low to moderate amounts of alcohol influences fasting insulin and glucose concentrations and insulin sensitivity in nondiabetic postmenopausal women. DESIGN, SETTING, AND PARTICIPANTS: Randomized controlled crossover trial of 63 healthy postmenopausal women, conducted at a clinical research center in Maryland between 1998 and 1999. INTERVENTIONS: Participants were randomly assigned to consume 0, 15, or 30 g/d of alcohol for 8 weeks each as part of a controlled diet. All foods and beverages were provided during the intervention. An isocaloric beverage was provided in the 0-g/d arm. Energy intake was adjusted to maintain constant body weight. MAIN OUTCOME MEASURES: Fasting insulin, triglyceride, and glucose concentrations, measured at the end of each dietary period; insulin sensitivity, estimated with a published index of glucose disposal rate corrected for fat-free mass based on fasting insulin and fasting triglyceride concentrations, compared among treatments with a mixed-model analysis of variance. RESULTS: A complete set of plasma samples was collected and analyzed for 51 women who completed all diet treatments. Consumption of 30 g/d of alcohol compared with 0 g/d reduced fasting insulin concentration by 19.2% (P =.004) and triglyceride concentration by 10.3% (P =.001), and increased insulin sensitivity by 7.2% (P =.002). Normal-weight, overweight, and obese individuals responded similarly. Only fasting triglyceride concentration was significantly reduced when comparing 0 and 15 g/d of alcohol (7.8%; P =.03), and no difference was found between consumption of 15 and 30 g/d of alcohol; however, there was a significant linear trend (P =.001). Fasting glucose concentrations were not different across treatments. CONCLUSIONS: Consumption of 30 g/d of alcohol (2 drinks per day) has beneficial effects on insulin and triglyceride concentrations and insulin sensitivity in nondiabetic postmenopausal women.