The body requires calcium to maintain healthy bones and perform a variety of critical metabolic functions. Calcium supplements can help reduce phosphate levels in people with kidney disease, prevent or treat osteoporosis and reduce symptoms of premenstrual syndrome, according to MedlinePlus. A variety of factors affect the absorption of different forms of calcium.
Absorption Factors
The specific amount of calcium absorbed from supplements depends on the total amount taken at a time, notes the National Institutes of Health Office of Dietary Supplements. Absorption decreases with increasing doses. The body can absorb the highest percentages of calcium from doses less than 500 mg. If you need more supplemental calcium, consider taking divided doses of 500 mg or less. Absorption also decreases with age. Infants and young children absorb as much as 60 percent of calcium consumed, while older adults absorb only 15 to 20 percent, according to the National Institutes of Health Office of Dietary Supplements. Food components that can inhibit calcium absorption include phytic acid in whole grains, legumes, nuts and seeds and oxalic acid in spinach, collard greens and beans. Vitamin D can boost calcium absorption.
Calcium Carbonate
Calcium carbonate is a widely available, inexpensive form of calcium supplement. Calcium carbonate contains 40 percent calcium by weight. The body absorbs calcium carbonate just as well as calcium citrate, another common form of calcium supplement. However, individuals with reduced stomach acid levels may not be able to absorb calcium carbonate as well as calcium citrate. Consuming calcium carbonate with food improves absorption.
Calcium Citrate
Calcium citrate, another common form of calcium supplement, contains 21 percent calcium by weight. Individuals with low levels of stomach acid caused by atrophic gastritis or other health conditions can absorb calcium citrate more easily than calcium carbonate, according to the National Institutes of Health Office of Dietary Supplements. Unlike other forms of calcium, the body absorbs calcium citrate just as well without food as with food.
Other Forms
Other common forms of calcium in supplements include calcium gluconate, calcium lactate and calcium phosphate. Fortified juices often contain calcium citrate malate. Taking these calcium supplements with food can improve absorption.
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