Dark chocolate was the clear winner, she says. She is due to present the findings at the Experimental Biology 2012 meeting in San Diego.

"Eat dark chocolate , not white chocolate ," says researcher Mee Young Hong, PhD, associate professor of exercise and nutritional sciences at San Diego State University. She compared dark and white chocolate , looking at health effects, such as improving cholesterol .

April 24, 2012 -- If you're eating chocolate for the health benefits -- and aren't we all? -- you must pick wisely, new research suggests.

Chocolate and Health Benefits: Study Details

Hong compared white chocolate, which has no cocoa solids, to regular dark chocolate containing 70% cocoa. The cocoa solids contain healthy compounds called flavonols. These have antioxidant and anti-inflammatory properties.

She also tested dark chocolate containing 70% cocoa that had been overheated or ''bloomed." ("You know when you leave chocolate in the [hot] car?" she asks. That's ''bloomed" -- melted and then maybe hardened again.)

She wanted to see if the melting would rob the dark chocolate of the health effects.

Hong's team assigned 31 men and women to eat about 1.7 ounces (a standard-size chocolate bar is about 1.5 ounces) of dark, white, or ''bloomed" dark chocolate every day for 15 days. Before and after the study, Hong's team measured blood pressure, blood sugar, and cholesterol.

Compared to those who ate white chocolate, those eating either dark chocolate had:

Lower blood sugar levels

Improved LDL or ''bad" cholesterol

Improved HDL or "good" cholesterol

She didn't find differences in blood pressure between the white chocolate eaters and the dark chocolate eaters.

As for why the dark chocolate may help blood sugar levels, Hong says its antioxidants may help the body use its insulin more efficiently to control blood sugar. This, in turn, helps to lower blood sugar levels naturally.

Compared to people who ate white chocolate, those who ate dark lowered their bad cholesterol by about 20%, Hong tells WebMD. Dark chocolate eaters increased their good cholesterol by 20%, compared to white chocolate eaters.

The white chocolate, but not the dark, made the skin blood flow slow down -- not a desirable quality. Skin blood flow is a way to measure how the blood vessels are functioning.

The study did not have industry funding.