Most calcium supplements are made from carbonate or citrate 51012. Each type has different characteristics that may make one more appropriate for you than the other. If you need extra calcium to maintain optimum bone health, consider some important factors when choosing the best form of calcium supplement to take 3.

Supplements Containing Calcium Carbonate

Calcium carbonate is the component in antacids like Tums and Rolaids. It's an alkaline-based compound derived in nature from sources like rocks, limestone, shells, pearls and snails. Calcium carbonate provides 35 to 40 percent elemental calcium per pill, according to Advanced Orthomolecular Research.

The absorption of calcium carbonate requires stomach acid because it has poor water solubility. This makes it appropriate if you suffer from excess stomach acid. Calcium carbonate should be taken once a day with a meal.

Supplements Containing Calcium Citrate

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Unlike the alkaline characteristic of calcium carbonate, calcium citrate has an acid base, making it the best form of calcium for older people with lower stomach acid 12. Calcium citrate has a lesser amount of elemental calcium at 20 percent, so doses must be taken twice per day 12.

Food and Nutrition Research conducted a study to determine whether a single dose of 1,000 milligrams of calcium carbonate would have the same absorption as two 500-milligram doses of calcium citrate in one serving 212. The trial was conducted to see if calcium citrate could be taken only once daily by patients who often forget to take their second dose 12. The results found that 1,000 milligrams of calcium carbonate powder had better absorption of total calcium than 1,000 milligrams of calcium citrate tablets 212. The conclusion was that calcium citrate is more effective splitting the dose and not taken all at once 12.

How Calcium Is Absorbed

The National Institutes of Health recommends that, after age 50, women need 1,200 milligrams of calcium daily; men need 1,000 milligrams daily 3. But not all calcium is absorbed by the body 6. Infants and young children absorb up to 60 percent calcium, but that amount decreases to 15 to 20 percent in adults and continues to decrease with age. In addition, calcium may be eliminated from the body in urine, feces and sweat by consuming excess sodium, caffeine and alcohol, which increases urinary excretion. According to Brigham and Women's Hospital, taking calcium supplements could compromise the absorption of iron, zinc and certain drugs, such as some antibiotics 510. Conversely, some drugs such as corticosteroids could increase calcium needs.

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Calcium and Vitamin D

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There has been much controversy in past studies regarding the benefits of calcium and vitamin D and fracture incidence in older adults 4. A new meta analysis by the Department of Orthopaedic Surgery in China was conducted in 2017 using a systematic search of clinical trials from the databases of PubMed, Cochrane Library and EMBASE. Results, published in the Journal of the American Medical Association, were that studies showed no significant associations between the incidence of fractures and calcium, vitamin D, or combined calcium and vitamin D supplements 810. Regardless of the doses of calcium or vitamin D, history of fracture, sex and dietary calcium intake, the results were generally consistent. The recommendation from these studies doesn't support the routine use of vitamin D with calcium supplements 10.

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Calcium Supplements

**Although it's best to meet your calcium needs with food sources, health conditions such as risk for osteoporosis may make calcium supplements helpful, but not all supplements are the same.** All calcium supplements are made by combining calcium with various salts, forming compounds that contain different amounts of elemental calcium, the calcium your body can actually absorb into the blood.

Calcium supplements come in a variety of forms including capsules, tablets and powders. Chewable and liquid forms, including fortified orange juices, are a good choice if you have trouble swallowing. Some calcium supplements come with multivitamins added, such as the effervescent Cal-C-Cap tablets 10. Be sure to discuss the need for calcium supplements with your doctor 10.

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