Which Calcium Supplement Is More Easily Absorbed?

Although foods are the best source of calcium, supplements can help you meet your daily calcium needs if you don't regularly consume calcium-rich foods. However, a number of factors affect their absorption. If you take these supplements, take steps to ensure that you absorb as much as possible of the calcium in your supplement.

Types

Calcium carbonate and calcium citrate are the most recommended calcium supplements, and both are well absorbed. If you have low stomach acid levels, however, calcium citrate is better absorbed. Other calcium supplements exist, but are less recommended. Supplements made from dolomite, bone meal and oyster shells can be contaminated with lead and other heavy metals, and calcium gluconate, calcium lactate and calcium phosphate supplements contain so little elemental calcium that you need to take large numbers of supplements to meet your calcium requirements.

Increased Absorption

Take your calcium with food, and split up your dose of calcium rather than taking it all at once. Take no more than 500 mg at a time, as the more calcium you take at once the less is absorbed. Estrogen, lactose and vitamin D also increase calcium absorption. Some supplements dissolve better than others, so look for those with USP on the label, since the U.S. Pharmacopeia requires pills with its seal to dissolve within 30 to 40 minutes, so they are better absorbed.

Decreased Absorption

Dietary fiber, phytates, oxalic acid, laxative use, tea, alcohol, caffeine, protein, excessive magnesium or phosphorus and certain medications, including anti-convulsants and corticosteroids, decrease calcium absorption. Age also affects calcium absorption, with infants absorbing more of the calcium they consume than older adults.

Considerations

If you take medication for indigestion, you may absorb calcium citrate best, and if you are deficient in magnesium, taking a magnesium supplement along with your calcium can improve absorption. You should take iron supplements and antibiotics at least two hours after taking your calcium supplements to improve absorption of both medications.