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Drink Up: More Coffee Could Lower Diabetes Risk

An extra cup of coffee was associated with a lower risk of Type 2 diabetes in a new study.
Image: Bubbles form on the surface of a cup of coffee in a cafe in New York
Bubbles form on the surface of a cup of coffee in a cafe in New York, April 11, 2014.CARLO ALLEGRI / Reuters

Go ahead and indulge in that extra cup of coffee. New research suggests that an extra cup of coffee is associated with a lower risk of Type 2 diabetes.

Researchers examined 20 years worth of data on diet, lifestyle, medical conditions and chronic diseases from three large U.S.-based observational studies and found that participants who said they increased their coffee consumption by more than a cup a day over a four year period had an 11 percent lower risk of Type 2 diabetes in the subsequent four years compared with those who made no changes in coffee consumption.

And it didn’t seem to matter how much coffee people drank initially or what other changes in diet and lifestyle they made. The results appear Thursday in the journal Diabetologia.

Previous studies have shown the protective effect of coffee, but this is the first to look at how the risk of diabetes might change if people modify their consumption over a defined period of time, Rachel Huxley, an author of some of those previous studies and a researcher at the University of Queensland, Australia, told NBC News.

The lifetime risk for developing Type 2 diabetes is substantial: 32.8 percent for men and 38.5 percent for women, according to national surveys. “So even a small lowering of relative risk, such as 11 percent, will have important public health implications,” Shilpa Bhupathiraju, the study’s lead author and a research fellow at Harvard School of Public Health, told NBC News.

The study doesn’t prove changes in coffee consumption cause changes in the risk of diabetes, a chronic condition that affects the way the body metabolizes sugar. To do that researchers would have to conduct expensive, difficult and long-term clinical trials. But the researchers controlled for conditions that raise the risk of diabetes and could have altered the results, such as high cholesterol and hypertension, and the results held.

Researchers say they’re not sure why coffee would affect the risk of developing diabetes. “Coffee contains a multitude of compounds, such as flavonoids and magnesium, that may have a role, but it is really guess work,” says Huxley.

Caffeine was not thought to be an important factor — even though decaf coffee drinkers and tea drinkers did not show the association. Bhupathiraju says that’s probably because decaf coffee and tea drinkers didn’t drink much to begin with and made few changes in their consumption, “So we didn’t have enough statistical power to detect associations,” she says.

Bhupathiraju says individuals who are at high risk of diabetes may want to consider having an additional cup of coffee a day, but cautions that a cup of coffee means 8 ounces, not a 12 ounce tall Starbucks drink or a 16 ounce grande. “And it’s not those big blended coffee drinks. We’re talking about black coffee, maybe with a little milk and sugar,” says Bhupathiraju.

Both she and Huxley stress that exercise, a nutritious diet and losing weight are the most important and proven ways to lower diabetes risk. Says Huxley: “Coffee isn’t a magic bullet.”