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Say it’s so, Joe: The potential health benefits -- and drawbacks –- of coffee.

Coffee may taste good and get you going in the morning, but what will it do for your health?

A growing body of research shows that coffee drinkers, compared to nondrinkers, are:

coffee beans

“There is certainly much more good news than bad news, in terms of coffee and health,” says Frank Hu, MD, MPH, PhD, nutrition and epidemiology professor at the Harvard School of Public Health.

But (you knew there would be a “but,” didn’t you?) coffee isn't proven to prevent those conditions.

Researchers don't ask people to drink or skip coffee for the sake of science. Instead, they ask them about their coffee habits. Those studies can't show cause and effect. It's possible that coffee drinkers have other advantages, such as better diets, more exercise, or protective genes.

So there isn't solid proof. But there are signs of potential health perks -- and a few cautions.

If you're like the average American, who downed 416 8-ounce cups of coffee in 2009 (by the World Resources Institute's estimates), you might want to know what all that java is doing for you, or to you.

Here is a condition-by-condition look at the research.

Type 2 Diabetes

Hu calls the data on coffee and type 2 diabetes "pretty solid," based on more than 15 published studies.

"The vast majority of those studies have shown a benefit of coffee on the prevention of diabetes. And now there is also evidence that decaffeinated coffee may have the same benefit as regular coffee,” Hu tells WebMD.

In 2005, Hu's team reviewed nine studies on coffee and type 2 diabetes. Of more than 193,000 people, those who said they drank more than six or seven cups daily were 35% less likely to have type 2 diabetes than people who drank fewer than two cups daily. There was a smaller perk -- a 28% lower risk -- for people who drank 4-6 cups a day. The findings held regardless of sex, weight, or geographic location (U.S. or Europe).

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