Randomized Trial Finds Modest and Mixed Effects of Alcohol on Cardiometabolic Markers in Adults with Type 2 Diabetes

To try to overcome the serious biases in observational studies of “moderate” drinking, investigators randomly assigned adults with type 2 diabetes to mineral water, red wine (17g of ethanol), or white wine (16g of ethanol) with dinner for 2 years. At baseline, participants were aged 40–75 years; drank no more than 1 drink in a week; had no past addiction, smoking, stroke, myocardial infarction, or recent surgery; didn’t use more than 2 insulin injections; had hemoglobin A1C 6.4%-<10%; and had no first-degree relatives with breast cancer. Two-year follow-up was 87%.

• HDL cholesterol levels increased by 2mg/dL more in the red wine (but not white) group than in the water group.
• The white wine (but not red) group had a decrease in fasting plasma glucose that was 17mg/dL larger than the water group.
• Decreases in glucose with wine were only significant among the 1 in 3 participants who were slow alcohol metabolizer homozygotes.

Comments:

The most troubling feature of this trial report is the stated conclusion of safety. Clearly even a 2-year trial of a carcinogen cannot prove safety. Regarding efficacy, we do not know if raising HDL levels with alcohol confers cardiovascular risk reduction; the effects are small, contrary to those hypothesized regarding red versus white wine; and, for glycemic control, limited to the minority of fast alcohol metabolizers. Whether drinking low amounts improves any real measure of health remains unknown. These results are clearly insufficient to support any recommendation to start drinking for health reasons.

Richard Saitz, MD, MPH

Reference:

Gepner Y, Golan R, Harman-Boehm I, et al. Effects of initiating moderate alcohol intake on cardiometabolic risk in adults with type 2 diabetes: a 2-year randomized, controlled trial. Ann Intern Med. 2015;163(8):569–579.