June 1, 2004 - Light to moderate alcohol drinkers appear to have an edge over teetotalers when it comes to diabetes risk, and now a new study explains why.
Researchers in Italy have shown that alcohol improves the body's resistance to insulin -- the hallmark of type 2 diabetes. The findings represent some of the first direct evidence to confirm what many large-population studies have indicated. While drinking alcohol may have many effects on carbohydrate metabolism, this study specifically quantifies the improvement in insulin action, writes researcher Angelo Avogaro, MD, PhD. People with type 2 diabetes are not able to use glucose effectively because of their body's resistance to insulin -- the hormone that allows glucose to be used by cells for energy.
"For people who can drink alcohol, the key is certainly moderation," Avogaro tells WebMD. "This study proves that alcohol has a direct effect on insulin sensitivity, and should be considered in cases where its use is not contraindicated."
Insulin Resistance Overcome
Avogaro and colleagues from the University of Padova Medical School in Italy, tested insulin sensitivity among eight healthy people and eight people with type 2 diabetes prior to and while they were drinking alcohol.
Insulin sensitivity was tested by checking tolerance to glucose while the participants drank 40 grams of alcohol administered as vodka 40% weight by volume -- the equivalent of about three drinks.
Drinking alcohol was shown to directly impact insulin's action in both groups, but the effect was much stronger among the people with diabetes. In people with type 2 diabetes, the study showed an improvement in insulin's action and other parameters such as fatty acid levels -- which may contribute to complications relating to diabetes and heart disease.
Avogaro tells WebMD that alcohol was able to normalize insulin activity in the volunteers with type 2 diabetes. But he explains that the effect was not caused by an increase in insulin secretion but rather an improvement in insulin resistance.
"It is noteworthy that alcohol can overcome the state of insulin resistant, the typical metabolic feature of these patients, without affecting beta cell secretion," he writes. Beta cells are the cells in the pancreas that secrete insulin.
The researchers conclude that "in the absence of a history of alcohol-related problems or other contraindications, we would encourage the use of small amounts of alcohol to improve insulin sensitivity and, perhaps, stave off potential cardiac complications of diabetes."
How Much Is too Much?
Nutrition researcher Frank Hu, MD, PhD, of the Harvard School of Public Health, has also studied the effect of alcohol on the risk of diabetes. He says the evidence from large-population studies is fairly consistent and shows a reduction in risk of 30% to 40% associated with moderate drinking -- similar to the reduction in heart disease risk associated with moderate alcohol consumption.
Hu tells WebMD that moderate drinking is generally defined as no more than two drinks per day for men and one drink for women. A standard drink, such as a 12-ounce bottle of beer, a 5-ounce glass of wine, or a 1.5-ounce shot of 80-proof spirits, has between 11 grams and 14 grams of alcohol.
The American Diabetes Association neither encourages nor discourages moderate alcohol consumption among diabetes patients.
But American Heart Association spokesman Nathaniel Clark, MD, says the fact that alcohol is also a source of empty calories can be a particular problem for people with type 2 diabetes.
"Weight control is a big issue with type 2 diabetes, and alcohol represents a significant source of calories with no nutritional value," he says. "It doesn't make much sense to drink two or three gin and tonics a night if you are trying to lose weight."
Clark characterizes the Italian study as interesting, but says that the findings must be confirmed in larger studies.
"This study is just too small to have a direct impact on clinical practice," he tells WebMD.