A dose of skepticism

For dark-chocolate lovers, the medical study findings couldn't have been more delicious: Their guilty pleasure can ward off heart disease.

But if it sounds too sweet to be true, it is. The logic doesn't just melt in your mouth: It melts under the skeptical eye of Robert Davis, Atlanta author of the new book "The Healthy Skeptic" (University of California Press, $21.95).

"The truth is that there have been small, short-term studies suggesting dark chocolate in large quantities may have some short-term, positive effects on the cardiovascular system, but it's unclear whether there are any long-term benefits, and that's what counts," says Davis, a health journalist who teaches at Emory University's Rollins School of Public Health. "It gets translated to say dark chocolate is good for you, and that is a huge exaggeration of the truth."

Based on other studies, chocolate, blueberries, almonds and even onions have catapulted to celebrity status, thanks to marketing, media and eager consumers, notes Davis, who urges a more critical eye.

"It's an alluring story, but if we hear one food has miraculous powers, we have to stop and think, 'This is too good to be true.' No food by itself has that kind of power," he says.

On the flip side, a study that suggested hair coloring could cause leukemia shouldn't set off a panic either, he says. In the end, use common sense, he advises.

"Don't smoke, and have a healthy diet and don't get bogged down by worrying about one food or another or worrying about using hair dye. These little nuggets of information can overwhelm us, and we lose sight of the big picture."

We recently caught up with Davis to ask him about some popular medical claims.

The claim: Blueberries will prevent Alzheimer's

The Healthy Skeptic: Blueberries have antioxidants. They are perfectly good to eat and one of the many fruits we should eat, but there's no basis to suggest that blueberries are better for you than strawberries or watermelon or that it will prevent Alzheimer's.

Bottom line: Stop fixating on any one fruit and focus on your overall diet and getting a variety of fruits and vegetables.

The claim: Red wine is good for your heart

The Healthy Skeptic: There is some evidence that a glass of wine every night may be good for your heart, but the risk of drinking too much is far greater than drinking just the right amount.

Bottom line: If you want to drink a glass or two of wine, that's fine and it may be beneficial, but any more is probably not a good idea.

The claim: Dark chocolate prevents heart disease

The Healthy Skeptic: Small, short-term studies — virtually all of them funded by the chocolate-candy industry — suggest dark chocolate, which contains antioxidants known as flavanols, may have some beneficial effects on your cardiovascular system when consumed in large quantities. This doesn't mean you are less likely to have a heart attack 10 or 20 years down the line.

Bottom line: There's no evidence a little chocolate now and then is bad for you. But remember: Chocolate should viewed as candy — not medicine.