These days, everything from waffles to fruit juice is fortified with calcium. But how much of this essential mineral do you need and what are the best sources?

Product labels are confusing. Some nutrients are only listed by weight--grams of fat or milligrams of sodium, for example. But others, which include calcium, iron, and vitamins, are listed as Percent Daily Values, based on a 2,000-calorie-a-day diet. According to the 1997 report Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride, the recommended daily intake of calcium varies for different age groups. Children ages 4 through 8 should have 800 milligrams of calcium per day; kids 9 to 18 should have 1,300 milligrams; adults 19 through 50 should have 1,000 milligrams; and adults 51 and over should have 1,200 milligrams.

Since the largest group of people requires 1,000 milligrams, food labels reflect that amount; therefore, if a label indicates the product provides 10 percent of the recommended calcium, it contains 100 milligrams. Allison A. Yates, Ph.D., R.D., director of the Food and Nutrition Board at the National Academy of Sciences' Institute of Medicine, says, "From my personal perspective, 1,000 milligrams works well--you know if you're dealing with older people, you need 120 percent, and if you're dealing with a 6-year-old, you need 80 percent."

If you peruse the supermarket, looking for good sources of calcium, you'll find almost every aisle offers calcium-fortified products; the selection includes cereals, crackers, breads, egg substitutes, pancake mixes, muffin mixes, orange juice, fruit punch, and cocoa powder. But are these enriched products as good for you as foods with naturally occurring calcium?

They can be. "My feeling is that fortification of foods that are generally nutritious is an excellent way to get calcium," says Bess Dawson-Hughes, M.D., professor of medicine and chief of the Calcium and Bone Metabolism Laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University. The key word, of course, is "nutritious." It's great that there are cookies with added calcium, but you shouldn't rely on them for a full day's supply.

Most of the calcium in food we eat does not get absorbed. When you take all your calcium in one slug, you don't absorb it nearly as efficiently as when you spread it out throughout the day. For that reason, it's important to eat a calcium-rich food at every meal.

It's easy to get your calcium quota without drinking milk or eating cheese. But who wants a peanut butter cookie without milk or a grilled cheese without the cheese? Your best bet is to combine natural calcium sources with some fortified ones.