Coffee: The New Health Food?

The bottom line: "People who already drink a lot of coffee don't have to feel 'guilty' as long as coffee does not affect their daily life," says Hu. "They may actually benefit from coffee habits in the long run."

In other words, consume enough caffeine -- whether it's from coffee or another source -- and you will likely run faster, last longer and be stronger. What's enough? As little as one cup can offer some benefit, but the real impact comes from at least two mugs, says Graham. By comparison, it'd take at least eight glasses of cola to get the same effect, which isn't exactly conducive for running a marathon.

But the harder you exercise, the more benefit you may get from coffee. "Unfortunately, where you see the enhancing effects from caffeine is in hard-working athletes, who are able to work longer and somewhat harder," says Graham, who has studied the effects of caffeine and coffee for nearly two decades. "If you a recreational athlete who is working out to reduce weight or just feel better, you're not pushing yourself hard enough to get an athletic benefit from coffee or other caffeinated products."

But you can get other benefits from coffee that have nothing to do with caffeine. "Coffee is loaded with antioxidants, including a group of compounds called quinines that when administered to lab rats, increases their insulin sensitivity" he tells WebMD. This increased sensitivity improves the body's response to insulin.

That may explain why in that new Harvard study, those drinking decaf coffee but not tea beverages also showed a reduced diabetes risk, though it was half as much as those drinking caffeinated coffee.

"We don't know exactly why coffee is beneficial for diabetes," lead researcher Frank Hu, MD, tells WebMD. "It is possible that both caffeine and other compounds play important roles. Coffee has large amounts of antioxidants such as chlorogenic acid and tocopherols, and minerals such as magnesium. All these components have been shown to improve insulin sensitivity and glucose metabolism."

Meanwhile, Italian researchers credit another compound called trigonelline, which gives coffee its aroma and bitter taste, for having both antibacterial and anti-adhesive properties to help prevent dental cavities from forming. There are other theories for other conditions.

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