What is it?
Calcium is the most abundant, essential mineral in the human body. Of the two to three pounds of calcium contained in the average body, 99% is located in the bones and teeth. Calcium is needed to form bones and teeth and is also required for blood clotting, transmission of signals in nerve cells, and muscle contraction. The importance of calcium for preventing osteoporosis is probably its most well-known role.
Where is it found?
Most dietary calcium comes from dairy products. The myth that calcium from dairy products is not absorbed is not supported by scientific research.1 2 Other good sources include sardines, canned salmon, green leafy vegetables, and tofu.
Why do athletes use it?*
Some athletes say that calcium
- helps prevent muscle cramps.
- helps to make their bones stronger.
What do the advocates say?*
Calcium is especially important for athletes because they are more likely to lose calcium, as well as other minerals, through perspiration.
In addition to being important for strong bones, calcium is required for muscle contraction. Without enough calcium you may experience muscle cramps.
How much is usually taken by athletes?
Calcium is important for achieving and maintaining optimum bone density. Some athletes, especially women with low body weight and/or amenorrhea, are at risk for serious bone loss and fractures.3 4 Contributing to this risk are the diets of these athletes, which are frequently deficient in calcium.5 All athletes should try to achieve the recommended intakes of calcium, which are 1,300 mg per day for teenagers and 1,000 mg per day for adults. Other uses of calcium for sports and fitness, including prevention or relief of sports-related muscle cramps, have not been studied.
Are there any side effects or interactions?
Constipation, bloating, and gas are sometimes reported with the use of calcium supplements.6 A very high intake of calcium from dairy products plus supplemental calcium carbonate was reported in the past to cause a condition called “milk alkali syndrome.” This toxicity is rarely reported today because most medical doctors no longer tell people with ulcers to use this approach as treatment for their condition.
People with hyperparathyroidism, chronic kidney disease, or kidney stones should not supplement with calcium without consulting a physician. For other adults, the highest amount typically suggested by doctors (1,200 mg per day) is considered quite safe. People with prostate cancer should avoid supplementing with calcium.
In the past, calcium supplements in the forms of bone meal (including MCHC), dolomite, and oyster shell have sometimes had higher lead levels than permitted by stringent California regulations, though generally less than the levels set by the federal government.7 “Refined” forms (which would include CCM, calcium citrate, and most calcium carbonate) have low levels.8 More recently, a survey of over-the-counter calcium supplements found low or undetectable levels of lead in most products,9 representing a sharp decline in lead content of calcium supplements since 1993. People who decide to take bone meal, dolomite, oyster shell, or coral calcium for long periods of time can contact the supplying supplement company to request independent laboratory analysis showing minimal lead levels.
Some studies have shown that calcium competes for absorption with a number of other minerals, while other studies have found no such competition. To be on the safe side, some doctors recommend that people taking calcium for long periods of time should also take a multimineral supplement.
One study has shown that taking calcium can interfere with the absorption of phosphorus, which, like calcium, is important for bone health.10 . Although most western diets contain ample or even excessive amounts of phosphorus, older people who supplement with large amounts of calcium may be at risk of developing phosphorus deficiency. For this reason, the authors of this study recommend that, for elderly people, at least some of the supplemental calcium be taken in the form of tricalcium phosphate or some other phosphorus-containing preparation.
Vitamin D’s most important role is maintaining blood levels of calcium. Therefore, many doctors recommend that those supplementing with calcium also supplement with 400 IU of vitamin D per day.
Animal studies have shown that essential fatty acids (EFAs) increase calcium absorption from the gut, in part by enhancing the effects of vitamin D and reducing loss of calcium in the urine.11
Lysine supplementation increases the absorption of calcium and may reduce its excretion.12 As a result, some researchers believe that lysine may eventually be shown to have a role in the prevention and treatment of osteoporosis.13
Are there any drug
interactions?
Certain medicines may interact with calcium. Refer to drug interactions for a list of those medicines.
*Athletes and fitness advocates may claim benefits for calcium based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on calcium. For more complete and detailed information, including references and safety information, see Calcium as a nutritional supplement.
1. Sheikh MS, Santa Ana CA, Nicar MJ, et al. Gastrointestinal absorption of calcium from milk and calcium salts. N Engl J Med 1987;317:532–6.
2. Levenson DI, Bockman RS. A review of calcium preparations. Nutr Rev 1994;52:221–32 [review].
3. Drinkwater BL, Bruemmer B, Chestnut III CH. Menstrual history as a determinant of current bone density in young athletes. JAMA 1990;263:545–8.
4. Nattiv A, Agostini R, Drinkwater B, Yeager KK. The female athlete triad: the inter-relatedness of disordered eating, amenorrhea and osteoporosis. Clin Sports Med 1994;13:405–18.
5. Manore MM. Dietary recommendations and athletic menstrual dysfunction. Sports Med 2002;32:887–901 [review].
6. Levenson DI, Bockman RS. A review of calcium preparations. Nutr Rev 1994;52:221–32 [review].
7. Burros M. Testing calcium supplements for lead. New York Times June 4, 1997, B7.
8. Bourgoin BP, Evans DR, Cornett JR, et al. Lead content in 70 brands of dietary calcium supplements. Am J Public Health 1993;83:1155–60.
9. Ross EA, Szabo NJ, Tebbett IR. Lead content of calcium supplements. JAMA 2000;284:1425–9.
10. Heaney RP, Nordin BEC. Calcium effects on phosphorus absorption: implications for the prevention and co-therapy of osteoporosis. J Am Coll Nutr 2002;21:239–44.
11. Kruger MC, Horrobin DF. Calcium metabolism, osteoporosis and essential fatty acids: a review. Prog Lipid Res 1997;36:131–51 [review].
12. Civitelli R, Villareal DT, Agnusdei D, et al. Dietary L-lysine and calcium metabolism in humans. Nutrition 1992;8:400–5.
13. Flodin NW. The metabolic roles; pharmacology, and toxicology of lysine. J Am Coll Nutr 1997;16:7–21 [review].