Dietary Calcium to Prevent Osteoporosis

Why Take Calcium?

In every major study of calcium supplementation, those who took extra calcium demonstrated either less bone loss or fewer fractures over time than the non-supplemented group. Generally adults do not consume enough calcium to equal that lost from bone, and frequently low calcium intake from childhood has left bones vulnerable even by the middle years.

Why is this a woman's problem?

Men get osteoporosis also, but to a far lesser extent than women. We see bone loss with age in all groups, but the loss of estrogen in women at menopause accelerates this loss in women. Men who take certain medications (such as steroids) lose significant bone strength.

Are other dietary factors important?

Yes - the more protein consumed, the more calcium is excreted in the urine. For each gram of protein consumed, about 1 to 1.5 mg of calcium is lost in the urine. An average woman may only need 50 grams of protein per day, but in the US, a woman may consume 200 grams! That would mean an extra 200mg or so of calcium lost. Given an average American diet with 400-500 mg per day of calcium, of which only about one-third is absorbed, this can make a significant difference. Excess salt and even caffeine may increase calcium excretion in the urine. These issues are especially important for women who have insufficient or borderline calcium intakes - they may shift the balance to an over-all calcium loss. This is one reason that calcium supplements are important in our society. See below for more information about supplements.

Can I get enough calcium in food?

Absolutely! The table below demonstrates the calcium content of common foods. You can get about 200mg from random foods. Keep in mind that total intake should be 1,000-1,200mg per day.

The really great thing about the above foods is that, as you can see, there are foods high in calcium which are not too high in calories. A bowl of Total cereal with a cup of low-fat milk and a glass of calcium-fortified orange juice would almost be a day's supply!

What about supplements?

There are all sorts of supplements, most available as a tablet. The most common is calcium carbonate, available as "Tums", or a generic store brand. Also available is calcium lactate, calcium citrate, etc. Most forms are well-absorbed, and specialty products such as "chelated calcium" are usually not worth the extra cost. Forms of calcium containing bone meal should be avoided because of often having unacceptable levels of lead.

Be aware that the "mg's" or milligrams, of calcium in a tablet is not the same as the milligrams of the calcium compound. A 500mg tablet of calcium carbonate, such as in "Tum's", contains 200mg of calcium. Be sure to read the back label if needed. It is the amount of calcium only which you need to compare to your daily requirements.

What about other nutrients - such as vitamin D and magnesium?

These are important also. Vitamin D is needed at about 200iu ("international units") to 400iu per day (the higher amount if you are older). A serving of dairy contains about 100iu. The body can make vitamin D if exposed to sunlight - about 10-15 minutes per day of sun on the hands and arms is probably enough (without sunscreen)in the summer or anytime of the year if you live south of a line drawn from Atlanta to Los Angeles. If you live in the north you cannot get enough sunlight during the winter to make adequate vitamin D, so supplements are needed. Some calcium supplements also come with vitamin D in them.

Magnesium is also important for bone strength. If you obtain calcium from foods, those usually contain magnesium as well. Grains, leafy green vegetables, etc., also contain magnesium and other important minerals. If you do not eat "whole foods" you might want to consider a general mineral supplement as well. Some calcium supplements come with vitamin D and magnesium. "Caltrate Plus" is one that has established a good reputation.

Are there problems with calcium supplements?

There can be - supplements, especially the "Tums" type calcium carbonate, act as antacids and can reduce the absorption of other minerals and some medications from the stomach. Of particular importance is tetracycline antibiotics and acid-blockers such as "zantac". Ask your pharmacist if any doubts. Calcium is better absorbed if taken with food, but it may actually impede the absorption of iron and other minerals by decreasing stomach acid. For this reason it is best to get calcium from food sources whenever possible. If a person taking calcium also battles iron-deficiency anemia they should take their calcium other than at mealtime and never with an iron supplement (which may be taken with extra vitamin C to improve absorption). In addition, calcium should not be taken with thyroid supplements - if you take thyroid hormone supplements keep several hours between that and your calcium.

How Much?

There can be negative consequences of taking too much calcium - specifically, it may lower absorption of other minerals. Getting 1200 mg per day is plenty. Use the daily calcium estimator to figure out approximately how much you get in your food, and take an appropriate amount to get you between 1200-1500 (food plus supplement). Many people do fine with 600mg extra per day. Although it is popular to recommend 1200 or 1500 mg of supplement per day, that amount is usually not warranted. Those who eat absolutely no dairy products and who cannot use calcium-fortified orange juice, soy cheese, etc, should probably take 1200 mg per day.

Information on this page was obtained from Goodhart & Shils' Modern Nutrition in Health and Disease, an excellent article in Nutrition Action Magazine from April, 1998, and from the:
USDA Food Nutrient On-line Database.

(c)1998 Dr. Stephen Blythe