Chocolate: as hearty as red wine.

Chocolate is a fatty food. So why don't unrefrigerated candy bars turn rancid as they sit on the shelf, the way so many other high-fat foods do? The answer, explains a trio of food chemists from the University of California, Davis, is that cocoa contains a number of potent flavonoids- pigments and other polyphenols that retard oxidation, which can make fats deteriorate.

In the body, oxidation transforms lipid-rich low-density lipoproteins (LDLs) in the blood into the foam cells that create artery-clogging plaque. That realization prompted Andrew L. Waterhouse and his UC-Davis colleagues to wonder how the flavonoids in chocolate compare to those in red wine. After all, several studies have indicated that a daily glass or two of these flavonoid-pigmented wines can cut dramatically an individual's risk of heart attack (SN: 3/30/96, p. 197).

In the Sept. 21 Lancet, Waterhouse's team confirms that cocoa powder extract indeed protects LDLs-the so-called bad lipoproteins-from oxidation. Its polyphenols, at a concentration of 5 micromoles per liter, cut oxidation of human LDLs by 75 percent in test-tube experiments. The extract's antioxidant potency roughly matches that of gallic acid, another potent antioxidant, and, based upon studies conducted by other scientists, it appears to outperform slightly the flavonoid blend in red wine.

So how much chocolate does one have to nosh for this effect? A 5-ounce glass of red wine contains about 210 milligrams of polyphenolic antioxidants. In comparison, Waterhouse's group reports, a cup of hot chocolate made with 2 tablespoons of cocoa would deliver 146 mg of antioxidants, and a 1.5-ounce chunk of milk chocolate, 205 mg.