By Alice Z. Lawrence, Fall 2003
Cooks take note: the way garlic is treated in the kitchen can affect its cancer-fighting properties.
Although a recent study showed that less than one clove a day may cut prostate-cancer risk in half, and other research links garlic to a lowered incidence of stomach, colon and possibly breast cancers, that all depends on its preparation, says John A. Milner, chief of the Nutritional Science Research Group at the National Cancer Institute.
Garlic’s active agents—allyl sulfide compounds—are produced when the clove is chopped or crushed. This breaks the cell walls and starts a cascade of chemical reactions (which also produce garlic’s characteristic smell) leading to the desired sulfides. But Milner found that heating the garlic immediately after chopping inactivated a crucial enzyme in the chemical chain.
Chopped garlic tossed directly into hot oil, or whole garlic cooked without crushing (or at least cutting off the top), will still impart the desired taste, but little or no cancer-fighting benefits. Once the compounds develop, however, they are quite stable and will withstand the heat of cooking. Milner’s advice: “Crush or chop the cloves, then let them sit for 10 or 15 minutes while you prepare other ingredients. This will give the anticancer compounds a chance to form.”
Garlic you buy in jars, already chopped, may be just as healthful. “When chopped garlic was stored in the freezer for weeks,” says Milner, “the compounds remained active.”