Moderate drinking has been associated in some studies with a lower risk of heart disease and type 2 diabetes. Certain risk factors for diabetes, such as increased insulin levels and a decreased ability of body cells to use insulin (insulin sensitivity), may be affected by alcohol consumption. Because women are at particular risk for heart disease after menopause, researchers in Maryland conducted a study to determine what effect moderate drinking would have on insulin levels and insulin sensitivity in postmenopausal women. Their results are published in the Journal of the American Medical Association.

Alcohol as part of a controlled diet

The researchers studied the effects of alcohol on circulating insulin levels and insulin sensitivity in 51 healthy, postmenopausal women. The women were randomly assigned to one of three treatment groups: one drink per day (15 grams alcohol), two drinks per day (30 grams alcohol), or no alcohol (these women were given a nonalcoholic beverage with the same amount of calories as the alcoholic beverages). The study consisted of three separate 8-week periods, so that every woman eventually participated in each of the three treatment groups by the end of the study.

The women lived at home, but followed a prescribed diet in which all food and beverages were provided by the research center. Those drinking the alcoholic beverages, which consisted of ethanol mixed with orange juice, were instructed to drink them 1 to 2 hours before bedtime.

Effect only seen with two drinks/day

At the end of each 8-week period, the women's blood samples were collected and analyzed for insulin, glucose, and for insulin sensitivity. Compared with no alcohol consumption, two drinks per day produced an average reduction of 19% in fasting insulin levels and significant improvement (7.2%) in insulin sensitivity. One drink per day did not significantly affect either insulin levels or insulin sensitivity.

Interpreting the results

While the results of this study show that moderate alcohol intake may improve insulin sensitivity, and, therefore, reduce the risk of diabetes, researchers do not recommend that women drink alcohol specifically for this reason.

There are several reasons for this. First, the women in this study followed a prescribed diet that was formulated to keep their weight stable. It's unknown whether moderate drinking would have had the same effects in women eating diets of their own choice. It's also not known whether a different type of alcoholic beverage than the one used in this study (ethanol mixed with orange juice) would produce similar results. And, finally, it's not known if the results would be similar for men or for premenopausal women.

The bottom line

Insulin sensitivity is a complex issue that continues to be studied by scientists for its effects on health and on disease risk. The bottom line? If you don't drink already, don't start. If you do choose to drink alcohol, do so in moderation and as part of a healthful diet.