NEW YORK (Reuters Health) - Coffee drinkers have a substantially lower risk of developing type 2 diabetes than people who abstain from the beverage, a new study shows.

This "striking" protective effect was seen in former coffee drinkers as well, Besa Smith and co-investigators at the University of California San Diego in La Jolla report.

"The growing body of literature definitely suggests strongly...that there is something there," she told Reuters Health in an interview. Just what that something is isn't clear, but it's probably not caffeine, she said, because the effect has also been observed with decaffeinated coffee.

Smith and her colleagues investigated 910 men and women, all of whom were 50 or older and free of diabetes when the study began.

When the subjects were followed-up about 8 years later, the former and current coffee drinkers were about 60 percent less likely to have developed type 2 diabetes.

The protective effects were still seen after the researchers adjusted the data for variations in physical activity, weight, blood pressure, smoking and sex among the subjects.

Coffee's protective effect was seen even among people who had impaired glucose tolerance, an early warning sign of diabetes, at the beginning of the study.

The researchers were unable to determine how much coffee people needed to drink to produce the protective effect. But study participants were generally not heavy coffee drinkers, Smith said.

"Given the increasing prevalence of obesity, impaired glucose tolerance, and diabetes, and the fact that the majority of adults in most of the Westernized world drink coffee daily, a coffee benefit could have widespread impact," she and her colleagues conclude. "Further investigation is warranted."