Calcium Supplements - Sources Of Calcium: Osteoporosis

Content provided by the Faculty of the Harvard Medical School

Calcium supplements

While experts recommend getting your nutrients from foods instead of supplements, you may find that it just isn't practical or possible for you to get all the calcium you need from your diet. In that case, a supplement can shore up your calcium intake and your bones. In fact, a 2002 analysis of several studies of postmenopausal women found that the women who took calcium and vitamin D supplements for at least two years were 23% less likely to suffer a spinal fracture.

A dizzying array of calcium supplements is available — so many, in fact, that choosing one can be tricky. You can choose from flavored chews, pills, chewable tablets, and liquids. When making a decision, it's wise to consider cost, convenience, and how well your body tolerates the supplement (see Table 4).

The calcium in supplements is found in combination with another substance, typically carbonate or citrate. (Some products combine calcium with phosphate, lactate, and gluconate, but these are less common and tend to be more expensive.)

Calcium carbonate tends to be the best value, because it has the highest amount of elemental calcium. Elemental calcium is the actual amount of calcium in each supplement. The compound calcium carbonate contains 40% calcium by weight, while calcium citrate is 21% calcium. This means that you may need to take more tablets of a calcium citrate product in order to meet your daily needs.

Because calcium carbonate requires stomach acid for absorption, it's best to take this product with food. Most people tolerate calcium carbonate well. However, some people complain of mild constipation or feeling bloated. Some well-known calcium carbonate products include Caltrate, Viactiv Calcium Chews, Os-Cal, Tums, Rolaids Calcium Rich, and Liquid-Cal.

On the other hand, calcium citrate is absorbed more easily than calcium carbonate and can be taken on an empty stomach. But as mentioned above, you may need to take more tablets to get your daily requirement. Calcium citrate products include Citracal and GNC Calcimate Plus 800.

In weighing your options, check the labels of products to see what the serving size is and what the "% Daily Value" for calcium is. The "% Daily Value" reflects how much elemental calcium is in the product. The Daily Value is set by FDA regulations and is not the same as the Recommended Dietary Allowance (RDA). Currently, the Daily Value for calcium is 1,000 mg — the RDA for people ages 19–50, not the 1,200 mg RDA for older adults. Since the "% Daily Value" for all calcium supplements is 1,000 mg, simply multiply the percentage listed by 10 to find out how much elemental calcium the product contains. For example, if the label says the product contains 40% of the Daily Value, it has 400 mg of elemental calcium.

You'll find that the serving size and % Daily Value vary from product to product. For example, one Viactiv Soft Calcium Chew for Women contains 500 mg of calcium, while two Tums E-X antacids provide 600 mg. The same company may offer several different supplements, with varying amounts of calcium. For instance, with Citracal Calcium Citrate Tablets, you'll need to take two tablets to get 400 mg of calcium, while another Citracal formula, Citracal Calcium Citrate Plus Vitamin D, yields 630 mg of calcium in two caplets. In addition, some supplements may include vitamin D while others don't.

Reading the labels with an eye toward cost and convenience may help you sift through your options. Would you find it inconvenient to take several tablets at a time? How many tablets or chews does the package contain, how many must you take at a time, and what is your cost per serving? While products that yield a high amount of calcium may seem to be the best bet at first blush, they may not serve you best. Because your body has difficulty absorbing more than 500 mg of calcium at a time, more may go to waste. So while you may think that you've met your daily requirements by taking that 1,000-mg calcium pill, you may actually be only halfway to your target.

Your taste is another factor. You may find that you're more likely to remember to take your calcium if it comes in a soft caramel square, rather than a flavorless pill. Of course, preferences vary from person to person. Some people enjoy tropical fruit or berry-flavored antacids, while others find them chalky.

Here are a few other things to keep in mind when choosing and taking a calcium supplement:

• Generally, calcium pills are better choices than multivitamins, which tend to have small amounts of elemental calcium.

• The National Osteoporosis Foundation recommends avoiding calcium products from unrefined oyster shell, bone meal, or dolomite that don't have the United States Pharmacopeia (USP) symbol on them, since these products have tended to contain higher levels of lead, a toxic metal.

• Because calcium, iron, and zinc supplements interfere with each other, take them several hours apart.

• Delay consuming calcium (either from food or supplements) for two to four hours after taking tetracycline antibiotics, as calcium can decrease their effectiveness. Also, ask your doctor or pharmacist whether a supplement will interact with any prescription medications you're taking.

• Don't exceed the daily dose recommended by the manufacturer, since that increases the risk for side effects.

• Vitamin D helps your body absorb calcium, but it's not necessary to take vitamin D and calcium at the same time. However, if you aren't getting enough vitamin D from sunlight, your diet, or your multivitamin, you may want to choose a calcium supplement that contains this ingredient.

• To test how well the calcium in a supplement will be absorbed, put a tablet in 4 ounces of white vinegar and stir occasionally. If it doesn't dissolve in 30 minutes, it's not likely to dissolve in your stomach, which means it will simply pass through your body without being used.

Last updated:	January 23, 2007