Chocolate may be good for something besides satisfying a sweet tooth.

A Penn State-led nutrition study has concluded that certain types of chocolate can have a positive effect on low-density lipoproteins (LDL), known as "bad cholesterol," by increasing their resistance to oxidation.

Containing flavonoids, an antioxidant found in sources such as tea, wine, apples and soybeans, chocolate is another plant-based food that inhibits LDL oxidation.

"Oxidized LDL is especially pathogenic," said Penny Kris-Etherton, distinguished professor of nutrition and leader of the study. "Once oxidation starts, a whole sequence of reactions occur that causes heart disease -- hardening of the arteries."

Using cocoa powder and dark chocolate, the study was conducted on 10 men and 13 women, ages 21 to 62, for two and a half months. Both experimental diets contained equal amounts of the stimulants caffeine and theobromine, while the chocolate was incorporated into milk, pudding snacks, cookies and brownies, according to a press release.

The subjects ate one of two diets which was either low in flavonoids or contained 22 grams of cocoa powder and 16 grams of dark chocolate, which are the preferred forms of chocolate because they are both rich flavonoid sources. The subjects remained on this diet for four weeks, then after a two-week break to their original eating habits, switched to the alternate diet for another four-week period.

As the first study to compare these contrasting diets, "Effects of Cocoa Powder and Dark Chocolate on LDL Oxidative Susceptibility and Prostaglandin Concentration in Humans" was published in the November issue of the American Journal of Clinical Nutrition, according to a press release. Kris-Etherton believes the real message of this study is that people should not feel guilty about eating chocolate. But she advised people with cholesterol problems to decrease their intake of saturated fat and cholesterol, while eating a diet rich in fiber, fruits and vegetables.

"I don't think people should rely on chocolate as a medicine," she said. "Chocolate is not a health food."

Cocoa powder contains twice the antioxidants of dark chocolate, which in turn has twice the amount of antioxidants when compared to milk, said Joe Vinson, professor of chemistry at the University of Scranton.

There are more antioxidants in chocolate than in most other things, but there is also a lot of fat, he said. People do not want to eat chocolate without sugar and fat, he added.

An ideal quantity of flavonoid-rich chocolate that does not have large amounts of fat and sugar would be 138 calories a day, Kris-Etherton said.

"That is not even the amount that would be found in a candy bar," she said, adding that a candy bar contains about 250 calories.

"Chronically eating chocolate gives you an antioxidant boost even when you are not eating it," Vinson said.

Findings from the University of Scranton, which collaborated with Penn State for this study, noted that a single 38-gram dose of chocolate had positive LDL effects, while Penn State studied the same dose over a longer period of time.

"We are not telling you to go binge on chocolate," Vinson said.

The University of Scranton plans to release the results of the short-term effects as well as the effect of decreased doses of chocolate.