A small, randomized controlled trial found that those with type 2 diabetes who consumed moderate amounts of alcohol daily had reductions in fasting glucose, but not postprandial glucose, when compared to their teetotaling days prior to the study.
Participants received either 150 ml (about 5 ounces) of wine, or non-alcoholic diet beer (control group), daily for three months. Beverages were consumed at dinner time.
The wine drinkers experienced an average reduction in fasting plasma glucose from 139.6 mg/dl before the study to 118.0 mg/dl after. Those with the highest HbA1c levels had the greatest reductions. Those in the control group experienced no change (136.7 to 138.6 mg/dl).
No notable adverse effects were reported, although those in the alcohol group did note an improved ability to fall asleep.
This was a short, small (n = 91 completed) trial with a fairly high dropout rate (17%). It supports hypotheses drawn from previous observational studies but its findings need, in turn, to be supported in further trials.
These results were reported in a Diabetes Care online, ahead of print article:
Glycemic effects of moderate alcohol intake among patients with type 2 diabetes: A Multi-center, randomized clinical intervention trial
Note: Alcohol is known to inhibit production of glucose in the liver, i.e. ethanol inhibits gluconeogenesis. Gluconeogenesis is one process the body uses to supply glucose to tissues during a fast, such as overnight.