Long-Term Coffee Consumption Significantly Reduces Type 2 Diabetes Risk

More than 125,000 study participants who were free of diabetes, cancer, and cardiovascular disease at the start of the study were selected from the on-going Health Professionals Follow-up Study and the Brigham and Women’s Hospital-based Nurses Health Study. Some 41,934 men were tracked from 1986 to 1998 and 84,276 women from1980 to 1998 via food frequency questionnaires every two to four years to assess their intake of both regular and decaffeinated coffee.

During the span of the study, 1,333 new cases of type 2 diabetes were diagnosed in men and 4,085 among the women participants. The researchers also found that for men, those who drank more than six cups of caffeinated coffee per day reduced their risk for type 2 diabetes by more than 50 percent compared to men in the study who didn’t drink coffee. Among the women, those who drank six or more cups per day reduced the risk of type 2 diabetes by nearly 30 percent. These effects were not accounted for by lifestyle factors such as smoking, exercise, or obesity. Decaffeinated coffee was also beneficial, but its effects were weaker than regular coffee.

The researchers note that caffeine, the best known ingredient in regular coffee, is known to raise blood sugar and increase energy expenditure in the short-term, but its long-term effects are not well understood. Coffee (both regular and decaffeinated) has lots of antioxidants like chlorogenic acid (one of the compounds responsible for the coffee flavor) and magnesium. These ingredients can actually improve sensitivity to insulin and may contribute to lowering risk of type 2 diabetes.

“This is good news for coffee drinkers, however it doesn’t mean everyone should run out for a latté,” said Frank Hu, senior author of the study and an associate professor of nutrition and epidemiology at the Harvard School of Public Health. “We still don’t know exactly why coffee is beneficial for diabetes, and more research is clearly needed.”

The research was supported by a grant from the National Institutes of Health.