Dairy products are the preferred sources of calcium. Children need 3 servings a day whereas pre-teens, teens and older adults need four servings a day. The following foods provide about 400 milligrams of calcium:

Sardines with bones -- 3 1/2 ounces
Yogurt, plain low-fat with milk solids added -- 1 cup
Yogurt, plain nonfat -- 1 cup
Tofu processed with calcium salts (content of tofu varies widely so consult label)
Cafe latte -- 12 ounces

300 milligrams of calcium:

Milk -- 1 cup, any kind
Yogurt -- 1 cup
Cheese -- 1 1/2 to 2 ounces
Part-skim ricotta cheese -- 1/2 cup
Salmon, canned with bones -- 6 ounces
Collard greens -- 1 cup cooked frozen
Soy milk -- 1 cup, varies with brand
Fortified orange juice -- 1 cup

200 milligrams of calcium:

Cheese -- 1 ounce (cheddar, part skim mozzarella, provolone, process American or swiss)
Ice cream or ice milk -- 1 cup
Turnip greens or kale -- 1 cup cooked
Cheese pizza -- one slice

100 milligrams of calcium:

Cottage cheese -- 3/4 cup low-fat or creamed
Broccoli -- 1 cup cooked, frozen
Navy or pinto beans -- 1 cup cooked
Taco -- one small
English muffin -- 1
Almonds -- 1/3 cup
Figs, dried -- 4
Frozen yogurt -- 1/2 cup

50 milligrams of calcium:

Black beans or lima beans -- 1 cup cooked
Clams,canned -- 2 ounces
Shrimp -- 3 ounces canned or 4 1/2 ounces fresh, steamed
Hamburger bun – 1
Orange -- 1

How Much Do We Need?

Most adults need 1,000 milligrams a day; adults over 50 need 1,200 milligrams. Children and adolescents need 1,300 milligrams to build and grow strong bones and calcium stores. Pregnant and breast-feeding women need only the amount recommended for their age. Most Americans do not get enough calcium in their diets, especially women.

When calculating the amount of calcium you get in your diet, keep in mind that certain dietary factors, lifestyle characteristics, medical conditions and medications can affect the absorption or excretion of calcium in your body. For example:

Calcium from foods rich in oxalates (such as spinach, sweet potatoes and beans) or in phytates (such as whole wheat bran, beans, nuts and soy isolates) may be absorbed poorly.

Protein and sodium in foods boost the amount of calcium excreted in urine, while phosphorus an vitamin D reduce the amount excreted in urine.

Caffeine reduces the absorption of calcium.

Cigarette smoking may decrease the absorption o calcium.

Diseases such as hyperthyroidism and diabetes, and medicines such as corticosteroids and glucocorticoids reduce the absorption of calcium, and increase the amount excreted in urine.

Alcohol in moderation does not appear to adversely affect calcium availability.

If you are not getting enough calcium in your diet, you should take a supplement. They do not provide the same overall nutrient benefits as foods, however. If you do take calcium supplements, follow these guidelines.

If you take high amounts, be sure to get at least 18 milligrams of zinc per day, too.

Avoid supplemental calcium from sources such as dolomite, oyster shell and bonemeal, which may be contaminated with lead or arsenic.

Take supplements with meals, and spread the daily dosage out over several meals instead of taking it all at once.

Read labels carefully; not all supplements contain the same amount of calcium. Supplements made from calcium carbonate have the most; 40 percent of the pill is the calcium itself. This number drops to 38 percent for pills made with calcium phosphate, to 21 percent for pills with citrate, and to 13 percent for lactate and 9 percent for gluconate. So you would have to make many more calcium lactate pills than calcium carbonate pills to get the same amount of calcium.

Is It Safe?

A calcium intake of up to 2,500 milligrams is safe for healthy people.