Background: Recommendations for moderate alcohol consumption remain controversial, particularly in type 2 diabetes mellitus (T2DM). Long-term randomized, controlled trials (RCTs) are lacking.
Objective: To assess cardiometabolic effects of initiating moderate alcohol intake in persons with T2DM and whether the type of wine matters.
Design: 2-year RCT (CASCADE [CArdiovaSCulAr Diabetes & Ethanol] trial). (ClinicalTrials.gov: NCT00784433)
Setting: Ben-Gurion University of the Negev–Soroka Medical Center and Nuclear Research Center Negev, Israel.
Patients: Alcohol-abstaining adults with well-controlled T2DM.
Intervention: Patients were randomly assigned to 150 mL of mineral water, white wine, or red wine with dinner for 2 years. Wines and mineral water were provided. All groups followed a Mediterranean diet without caloric restriction.
Measurements: Primary outcomes were lipid and glycemic control profiles. Genetic measurements were done, and patients were followed for blood pressure, liver biomarkers, medication use, symptoms, and quality of life.
Results: Of the 224 patients who were randomly assigned, 94% had follow-up data at 1 year and 87% at 2 years. In addition to the changes in the water group (Mediterranean diet only), red wine significantly increased high-density lipoprotein cholesterol (HDL-C) level by 0.05 mmol/L (2.0 mg/dL) (95% CI, 0.04 to 0.06 mmol/L [1.6 to 2.2 mg/dL]; P < 0.001) and apolipoprotein(a)1 level by 0.03 g/L (CI, 0.01 to 0.06 g/L; P = 0.05) and decreased the total cholesterol–HDL-C ratio by 0.27 (CI, −0.52 to −0.01; P = 0.039). Only slow ethanol metabolizers (alcohol dehydrogenase alleles [ADH1B*1] carriers) significantly benefited from the effect of both wines on glycemic control (fasting plasma glucose, homeostatic model assessment of insulin resistance, and hemoglobin A1c) compared with fast ethanol metabolizers (persons homozygous for ADH1B*2).
Across the 3 groups, no material differences were identified in blood pressure, adiposity, liver function, drug therapy, symptoms, or quality of life, except that sleep quality improved in both wine groups compared with the water group (P = 0.040). Overall, compared with the changes in the water group, red wine further reduced the number of components of the metabolic syndrome by 0.34 (CI, −0.68 to −0.001; P = 0.049).
Limitation: Participants were not blinded to treatment allocation.
Conclusion: This long-term RCT suggests that initiating moderate wine intake, especially red wine, among well-controlled diabetics as part of a healthy diet is apparently safe and modestly decreases cardiometabolic risk. The genetic interactions suggest that ethanol plays an important role in glucose metabolism, and red wine's effects also involve nonalcoholic constituents.
Primary Funding Source: European Foundation for the Study of Diabetes.