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.