– A. Dembowski, Pittsburgh

ANSWER: Chocolate has been touted as “the new red wine” for its putative health benefits. The excitement centers on a class of compounds called flavonoids, which are antioxidants. Raw cocoa is one of the richest known sources of flavonoids, with more than 10 percent flavonoids by weight.

Studies indicate that isolated flavonoids, or chocolate that contains flavonoids, may have favorable effects on five risk factors associated with heart disease.

First, flavonoids scavenge free radicals, thereby inhibiting the oxidation of low-density lipoprotein (LDL). This process is beneficial because oxidation of LDL promotes the formation of plaques – deposits – in the arteries. Second, flavonoids inhibit another early event in plaque formation – the adherence of white blood cells to the lining of the arteries.

Third, they increase high-density lipoprotein (HDL), which helps remove cholesterol from the body. Fourth, like aspirin, flavonoids reduce the reactivity of blood platelets so the platelets become less likely to stick together to form a blood clot. Fifth, flavonoids increase nitric oxide levels, which dilates the blood vessels and reduces blood pressure.

Some evidence suggests that flavonoids are protective against cancer and possibly neurodegenerative diseases. They have also been shown to decrease insulin resistance.

However, all the support for the health benefits of flavonoids comes from epidemiological studies and short-term experimental studies. Epidemiological studies are problematic because they compare naturally occurring populations, which may differ in more than just their cocoa consumption habits. So far, no long-term experimental studies have addressed the health benefits of chocolate consumption.

Not all chocolate is created equal. The flavonoid concentration depends on the variety of cocoa plant and the growing conditions. By far the most important factor is how the beans were processed. Most chocolate products contain little or no flavonoids because flavonoids are destroyed by fermentation, roasting and treatment with alkali. Experimental studies of chocolate consumption often use non-commercially available high-flavonoid chocolate.

If otherwise processed the same way, dark chocolate contains more flavonoids than milk chocolate. White chocolate does not contain any cocoa solids and is therefore devoid of flavonoids.

Sherry Seethaler is a UCSD science writer and educator. Send scientific questions to her at Quest, The San Diego Union-Tribune, P.O. Box 120191, San Diego, CA 92112-0191. Or e-mail sseethaler@ucsd.edu. Please include your name, city of residence and phone number.