Several studies have shown that moderate consumption of wine is associated with a lower risk of type 2 diabetes. But is wine the cause, and what specifically in the wine? Two new studies suggest wine does play a role and that chemicals in the grapes may help.
Previous studies have postulated that the lower rate of type 2 diabetes among moderate alcohol drinkers is due to a healthier lifestyle. This is unsurprising since drinkers tend to be more dedicated to exercise than their peers. For one of the studies, slated for publication in American Journal of Clinical Nutrition, a team of researchers at Wageningen University in the Netherlands analyzed the issue by looking at data drawn from the Dutch European Prospective Investigation into Cancer and Nutrition (EPIC-NL), a larger health study of more than 520,000 people in 10 European countries.
The Wageningen team chose data from 35,625 adult subjects who were considered to be lower on the risk scale for developing type 2 diabetes and heart disease (the two are closely correlated). Risk-lowering factors included optimal weight, regular exercise of more than 30 minutes per day, not smoking and a healthy diet, according to the Dietary Approaches to Stop Hypertension (DASH) protocols, a regime supported by the U.S. Department of Health and Human Services. The DASH diet focuses on reducing sodium and eating more grains, fruits and vegetables. Moderate drinking women have no more than a drink per day—1.5 ounces of 80-proof distilled spirits, one 5-ounce glass of wine or one 12-ounce beer—while men are allowed up to two.
After analyzing 10 years’ worth of data, including 796 cases of type 2 diabetes, the researchers concluded that the lower rate of the disease among drinkers cannot be explained by a healthier lifestyle alone. Alcohol, in some way, contributed directly to a lower incidence of the disease—drinkers had a roughly 40 percent lower risk compared to abstainers.
While the Dutch study does not explain why alcoholic beverages may lower risk, another study suggests that it may not be the alcohol alone. Research from the University of Michigan finds that eating grapes seems to slow development of high blood pressure and insulin resistance. Both are the leading precursors to heart disease and type 2 diabetes. Together, the two create a condition known as metabolic syndrome, which affects 50 million Americans.
In findings presented at the Experimental Biology convention in Anaheim, Calif., the Michigan team found that rats fed powder made from table grapes showed more favorable levels of blood sugar in the blood stream and improved glucose tolerance.
The effect is thought to be due to phytochemicals, which occur naturally in grapes and wine and include tannins, anthocyanins and resveratrol. Rats eating table grapes saw less arterial inflammation and oxidative damage.
"The possible reasoning behind the lessening of metabolic syndrome is that the phytochemicals were active in protecting the heart cells from the damaging effects of metabolic syndrome," said Steven Bolling, a heart surgeon at the university and head of the Cardioprotection Research Laboratory. One caveat—the study was funded in part by the California Table Grape Commission; the researchers declared the commission played no role in the study’s design and subsequent analysis.
Bolling adds that the results may be translatable to humans and suggests following a lifestyle pattern similar to the one found healthiest in the Dutch study. "Although there’s not a particular direct correlation between this study and what humans should do, it’s very interesting to postulate that a diet higher in phytochemical-rich fruits, such as grapes, may benefit humans."