The best insurance against osteoporosis appears to be frequent exercise of the bones that we want to keep strong, and a well-rounded diet that is rich in vitamins and minerals, moderate in salt and meat, and includes a variety of calciumcontaining foods. Milk is certainly a valuable one, but so are dried beans, nuts, corn tortillas and tofu (both processed with calcium salts), and several greens — kale, collards, mustard greens.