"We're coming from a situation where coffee had a very negative health image," says Rob van Dam, of the Harvard School of Public Health, who has conducted studies on coffee consumption and diabetes.

All the same, he adds: "It's not like we're promoting coffee as the new health food and asking people who don't like coffee to drink it for their health."

Dr. van Dam participated in a "controversy session" on coffee at the Experimental Biology 2007 meeting under way in Washington DC. Also involved was Lenore Arab, of the David Geffen School of Medicine at UCLA, presenting results of a review of nearly 400 studies investigating coffee consumption and cancer risk.

There's evidence, Arab notes, the beverage may protect against certain types of colon cancer as well as rectal and liver cancer, possibly by reducing the amount of cholesterol, bile acid and natural sterol secretion in the colon, speeding up the passage of stool through the colon (and thus reducing exposure of the lining of the intestine to potential carcinogens in food), and by other mechanisms.

However, Arab did find evidence that coffee may increase the risk of leukemia and stomach cancer, with the case for leukemia being strongest.

The findings suggest people who may be vulnerable to these risks -- for example, pregnant women and children -- should limit coffee consumption, says van Dam.

He and colleagues are conducting a clinical trial to get a clearer picture of the diabetes-preventing effects of coffee, which were first reported in 2002. Since then, he notes, there have been more than 20 studies on the topic.

Van Dam and his team are also looking for which of the "hundreds to thousands" of components of coffee might be responsible for these effects. It's probably not caffeine, he says, given that decaf and caffeinated coffee have similar effects on reducing diabetes risk.

His top candidate, he says, is chlorogenic acid, an antioxidant that slows the absorption of glucose in the intestines.

From the May 9, 2007, Prepared Foods e-Flash