What happens if you drink to much coffee?

Java

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

• less likely to have type 2 Diabetes, Parkinson's disease, and dementia
• have fewer cases of certain cancers, heart rhythm problems, and strokes

"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.