It's too soon to prescribe coffee as a health tonic, but researchers have found that downing half a dozen cups a day appears to lower the chances of developing Type 2 diabetes.
When compared with coffee abstainers, men who consumed six or more cups of caffeinated coffee daily reduced their risk of developing adult onset diabetes by 50%. Among women, the reduction was 30%. Even decaffeinated coffee reduced risk about 20%, said senior study author Dr. Frank B. Hu, an associate professor at the Harvard School of Public Health.
Hu and his colleagues monitored more than 126,000 participants in two large studies of health professionals. The men and women, who were free of cancer, heart disease or diabetes at enrollment, were surveyed regularly about consumption of caffeinated and decaffeinated coffee and other beverages. (About 50% of Americans drink coffee, averaging about two cups a day.) The researchers then looked at which of them developed diabetes.
The finding that java may protect against diabetes is good news for coffee drinkers, "but it doesn't mean everyone should go out and indulge themselves," Hu said.
In the short term, caffeine stimulates the nervous system and raises blood sugar, heart rate and blood pressure while boosting calorie-burning. It also impairs the ability of insulin to break down sugar. The long-term effects remain poorly understood, although Hu noted that people develop tolerance to caffeine's immediate effects within three to four days.
Coffee's effect on diabetes risk may relate to compounds other than caffeine, suggests the study in the Jan. 6 Annals of Internal Medicine. Regardless of caffeine content, coffee contains antioxidants such as chlorogenic acid, which can improve sensitivity to insulin and reduce absorption of glucose from the intestines. The magnesium, potassium and niacin improve insulin sensitivity.