Dietary calcium

Calcium is the most abundant mineral in the body. It occurs in some foods, is added to others, is present in some medicines such as antacids, and is available as a dietary supplement; it makes up much of the structure of bones and teeth.

In the body

Calcium keeps tissue rigid, strong and flexible, which allows normal movement. A small amount in the blood and tissues regulates the narrowing and widening of blood vessels, muscle function, blood clotting, nerve signals and the release of hormones. Vitamin D is needed for the gut to absorb calcium by active transport and to keep blood calcium at an adequate level.

Food and supplements

Milk, yoghurt and cheese contain a lot of calcium. Some vegetables such as kale, broccoli and Chinese cabbage, and canned sardines and salmon with bones, also contain it, and many fruit juices, milk substitutes, tofu and cereals are fortified with it. About 30% of the calcium in dairy products and fortified foods is absorbed; from some plants much less is absorbed, because they contain compounds that bind calcium into indigestible salts.

Supplements usually contain calcium carbonate or calcium citrate. How much calcium is absorbed from them depends on the form and on the total amount of calcium taken at one time.

How much

In the United States, the recommended intakes for calcium are 1,000 to 1,200 mg a day for adults and 200 to 1,300 mg for infants, children and adolescents, depending on age.

Too little

A lack of calcium can lead to osteoporosis, with weak, fragile bones and a higher risk of falls and fractures. It can also cause rickets in children and osteomalacia, softening of the bones, although these are more often caused by a lack of vitamin D. Women after the menopause and people who avoid dairy products are more likely to get too little calcium.

Too much

Higher intakes of calcium from supplements might increase the risk of kidney stones, and some research suggests that calcium supplements could raise the risk of cardiovascular disease. The tolerable upper intake level is 2,000 to 2,500 mg a day for adults, depending on age.

Interactions with medicines

Calcium supplements may interact with some medicines, and some medicines may affect calcium levels; examples are dolutegravir, levothyroxine, lithium and quinolone antibiotics.

Products containing it

• All Day Fit A-Z Compact tablets (S 06)
• Calcium capsules (D 245)
• Fito 40 capsules (S 07)