A small square of dark chocolate daily protects the heart from inflammation and subsequent heart disease, a new study of Italians suggests. Milk chocolate might not do the job.

However, this guilty pleasure has a limit.

Specifically, only 6.7 grams of chocolate per day (or 0.23 ounces) represents the ideal amount, according to results from the Moli-sani Project, one of the largest health studies ever conducted in Europe. For comparison, a standard-sized Hershey's Kiss is about 4.5 grams (though the classic Kiss is not made of dark chocolate) and one Hershey's dark chocolate bar is about 41 grams (so a recommendation might be one of those weekly).

Chronic inflammation of tissues in the circulatory system is a risk factor for cardiovascular disease, such as myocardial infarction or stroke. So doctors strive to keep patients' inflammation under control. One marker for inflammation in the blood is called C-reactive protein.

The researchers found a relationship between dark chocolate intake and levels of this protein in the blood of 4,849 subjects in good health and free of risk factors (such as high cholesterol or blood pressure, and other parameters). The findings are detailed in the latest issue of the Journal of Nutrition.

"We started from the hypothesis that high amounts of antioxidants contained in the cocoa seeds, in particular flavonoids and other kinds of polyphenols, might have beneficial effects on the inflammatory state," said Romina di Giuseppe, lead author of the study. "Our results have been absolutely encouraging: People having moderate amounts of dark chocolate regularly have significantly lower levels of C-reactive protein in their blood. In other words, their inflammatory state is considerably reduced." The inflammation reduction that the researchers observed controlled for other confounding variables such as wine or produce intake.

Previous studies have found that chocolate might be good for you, though doctors usually warn that it is more important to focus on one's overall diet when it comes to health. One health study found that blood platelets among chocolate-lovers were less likely to clot together in dangerous clumps.

Other studies have found a host of diet and exercise changes that can help a person beat the odds of death. Clearly, no single change is a guarantee of long life.

With chocolate, moderation is key, the new study found.

"The best effect is obtained by consuming an average amount of 6.7 grams of chocolate per day, corresponding to a small square of chocolate twice or three times a week. Beyond these amounts the beneficial effect tends to disappear," di Giuseppe said.

The milk in milk chocolate interferes with polyphenols, so the team kept that out of the study.

"We consider this outcome as the beginning of a large series of data which will give us an innovative view on how [to achieve] prevention in everyday life, both against cardiovascular disease and tumors," said Licia Iacoviello, head of the Laboratory of Genetic and Environmental Epidemiology at the Catholic University of Campobasso and responsible for the Moli-sani Project.

The Moli-sani Project is funded by the Pfizer Foundation.