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December 2, 1999
Catching Up on Calcium
How much do you need?
By Elizabeth Smoots, M.D.

Most of us fall short when it comes to getting enough calcium. The average American diet contains only half the calcium needed for good health. That's why osteoporosis -- a leading cause of weak, brittle bones -- is so common.

Osteoporosis makes people susceptible to fractures, shrinking stature, and disabling pain. An estimated 50 percent of women over the age of 50 will have an osteoporosis-related fracture. Men are not exempt, usually developing osteoporosis at a slightly older age. In addition, the majority of children aren't getting enough calcium to prevent bone disease later in life. With proper planning, however, it's easy to meet your body's requirement for this vitally important nutrient.

How much do you need?

It's critical to consume enough calcium to keep your bones strong and in good repair. We also need calcium for several other essential functions: muscle contraction, blood clotting, sending nerve impulses, and regulating our heartbeat and blood pressure.

Without sufficient calcium in the bloodstream to maintain these vital functions, our body takes calcium from our bones. Over time, this bone loss leads to osteoporosis. Studies have also linked calcium deficiency to tooth loss, high blood pressure, toxemia of pregnancy, and colon cancer.

For these reasons, the Institute of Medicine recommends that people consume the following amounts of calcium each day:

  • Men and women -- 1,000 mg before age 50, 1,200 mg after age 50.
  • Pregnant or lactating women -- 1,000 mg (or 1,300 mg if under age 19).
  • Children -- 500 mg for ages 1-3 years, 800 mg for ages 4-8, 1,300 mg for ages 9-18.

Best dietary sources

It's preferable to get your calcium from food, which contains many nutrients necessary for healthy bones. Consult the table below for the calcium content of dairy products and other calcium-rich foods. Add 300 mg for each serving you generally consume in a day to determine your total calcium intake. Then compare this number with the amount recommended for your age.

One serving contains about 300 mg of calcium:

Milk, whole or skim

1 cup


1 cup


1.5 oz

Soy milk

1 cup

Orange juice, calcium fortified

2 oz

Broccoli, kale, and other dark greens

2 cups

Salmon, canned

6 oz


3 oz

Tofu, calcium set (brands vary)

3-6 oz

Choosing a supplement

If you aren't getting enough calcium from your diet, you may want to consider taking a supplement. Most products work equally well, but be wary of generic or house brands that may be difficult to digest. Check the label for the amount of elemental calcium -- the part your body actually absorbs.

Many widely used supplements contain calcium carbonate. For people who can't tolerate this form, calcium also comes as a citrate, gluconate, lactate, or phosphate. Avoid supplements made from bone meal or dolomite, which may contain lead.

Calcium is best absorbed in divided doses taken between meals. Seniors and people taking medicine for indigestion or acidity should take calcium with food. Be sure to take vitamin D as well -- 400 IU (International Units) a day, 600 IU for seniors -- to help your body absorb calcium.

Consult with your primary care provider before taking calcium on a regular basis. Excess calcium can be harmful for people who have certain conditions, such as those that cause high blood calcium or kidney stones. It can also interfere with the absorption of iron or tetracycline, an antibiotic. Taking supplemental calcium tends to cause constipation, so drink plenty of water.