Can a Cup of Coffee Prevent Type 2?

You probably know that coffee seems to help wake you up in the morning—and afternoon, and sometimes in the evening, too. But did you know it might help prevent diabetes?

Studies examining the links between diet and diabetes risk have shown that coffee drinkers have a slightly reduced risk of cardiovascular disease, cancer, Parkinson’s disease—and type 2 diabetes. Of all the foods we consume, “coffee has the most potential to prevent type 2 diabetes,” says Marilyn Cornelis, PhD, a nutritionist and assistant professor at Northwestern University Feinberg School of Medicine. “With diabetes, the more coffee the better, according to epidemiological studies.”

Coffee is an important source of caffeine, but it’s also got other chemicals that might be protective. The complex aromas that coffee buffs savor come from hundreds of different chemical compounds released in the roasting process, for example, and coffee is known to contain high levels of antioxidants. When those chemicals are ingested, they interact with the body in ways we don’t yet understand — therefore the mystery behind coffee’s protective effects. In technical terms, those smaller elements are known as “metabolites,” after “metabolism,” the process of breaking down nutrients into components we can use.

It’s time to rethink coffee’s reputation as a bad habit. This year, the Food and Drug Administration acknowledged coffee’s benefits for the first time and suggested five cups as a healthy upper limit, more than in the past. So why not encourage everyone in America to drink coffee? “In general, people are already consuming the amount they appear to tolerate,” Cornelis says. “If someone’s had too much coffee, they can tell.”

Thanks to their genes, some people are simply better at metabolizing caffeine. For example, some people can down an espresso after dinner and sleep soundly all night, while others get the jitters all day from a single cup with breakfast. Someone who metabolizes caffeine faster is going to get less of a jolt per cup and be more likely to drink more coffee each day—and therefore might get more of the chemicals that reduce diabetes risk.

Most of the studies in people and animals have used black coffee, rather than sugary, milky concoctions. The extra calories in a Frappucino, in other words, probably offset any benefits the coffee inside may convey. “With this in mind, black coffee would be the preferred choice,” says Cornelis.