Originally made from camel's milk, kefir comes from high in the Caucasus — a 750-mile-long mountain range between the Caspian and Black seas. Today, however, it's more commonly produced from cow's milk. It's a slightly sour brew of fermented milk, most of which contains about 2 1/2 percent alcohol. Kefir is reminiscent in both taste and texture of a liquid yogurt. It's available in cartons or bottles in health-food stores. See also kumiss.