The body needs calcium to build and maintain strong bones and teeth, transmit nerve signals, support muscle contractions and many other functions. A well-balanced diet can provide all the calcium the body needs. However, if conditions such as osteoporosis occur it may be necessary to use supplements to help prevent fractures. There are many kinds of calcium tablets available but some are absorbed better than others, depending on how they are taken.
Forms of Calcium
Calcium carbonate and calcium citrate are the two most common forms of calcium found in supplements and both are absorbed equally well. Any form of calcium must dissolve in the stomach before it can be absorbed. Patients with conditions that cause a reduced level of stomach acid may absorb calcium citrate better, says the Office of Dietary Supplements because calcium citrate requires less stomach acid than calcium carbonate to break down. To test how well a supplement is absorbed; place a tablet in glass of vinegar, which will simulate an acidic environment; stir it occasionally and see if it fully dissolves within a 30 minute period. If it does not dissolve in the glass it may not dissolve in the stomach.
Taking Tablets with Food
The rate of absorption is also affected by how much calcium is taken and if it is taken with or without food. According to the New York State Department of Health, all calcium tablets are absorbed better if they are taken in small doses of 500 mg or less at a time. In addition, calcium carbonate should be taken with food to improve absorption rates while calcium citrate can be taken with or without food. Some patients experience gastrointestinal side effects when taking calcium on an empty stomach, so food may need to be eaten no matter what type of tablet is used. If side effects occur, the dose of calcium may need to be reduced to 200 to 300 mg at a time.
USP Symbol
Some calcium tablets may be manufactured from unrefined oyster shell, bone meal or dolomite. However for safety it is always best to stick to doctor recommended products or supplements with the "USP Verified Mark" or United States Pharmacopeia symbol. This symbol is found on products that have been tested and are known to dissolve in the stomach so they can be absorbed. In addition, supplements that are in chewable or liquid form are better because they begin to break down before reaching the stomach.
Considerations
Along with calcium carbonate and calcium citrate; supplements may also contain calcium gluconate and calcium lactate. All are absorbed equally well yet all contain varying amounts of calcium. This is known as elemental calcium, which is the amount of calcium the product actually provides. It is important to read each product's label to see how much elemental calcium it contains. In addition, while it may be necessary to take food with the tablet, certain foods can interfere with absorption rates. The University of Maryland Medical Center suggests refraining from eating foods high in oxalate or phytate such as spinach, beet greens, peas, pinto beans, navy beans and wheat bran; or high amounts of protein at the same time as taking a calcium tablet. Caffeine and foods high in sodium may also slow down absorption rates.
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