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Calcium is a mineral that is stored in the bones and is necessary for bone growth and strength. It also benefits the nervous system, muscles and heart. As your body ages, its ability to absorb calcium decreases, even though its need for calcium does not diminish. If you are older and also have a diet that lacks adequate calcium, both factors limit the amount of the mineral available for your body to use.

Calcium deficiency in older adults causes changes in the bones called osteomalacia and osteoporosis. Osteomalacia is an overall decrease in bone density. Osteoporosis (which occurs most frequently in thin, small-boned or white women) is a condition in which the bones become so weak that they are more likely to break or become deformed.

Getting the right amount of calcium

How much calcium do you need? The recommended dietary allowance (RDA) for calcium is 1,200 milligrams (mg) per day for men and women over the age of 50. Public Citizen thinks that this is a safe and desirable intake for all adults. It will not necessarily protect patients against the fractures and deformity of osteoporosis, but it may help and is unlikely to do any harm. We do not recommend taking more than 1,500 mg per day, since the greater amount has no advantages and can cause some dangerous adverse effects (see "Adverse Effects" section on this page).

The best way to get calcium is to eat foods that are rich in it (see “Foods High in Calcium” box at the top of this page). In particular, you can increase your calcium intake by drinking milk and adding liquid or powdered milk to almost any cooked food (you can use low-fat or nonfat milk if you want to keep your fat intake down). If you cannot get enough calcium from your diet (e.g., eating yogurt), take a calcium supplement. However, if you have a history of kidney stones, do not increase your calcium intake without talking with your doctor first.

Side effects

Britain's Expert Group on Vitamins and Minerals concluded that:

In humans, the main adverse effect associated with high levels of calcium intake is milk-alkali syndrome (MAS), resulting in hypercalcaemia [increased calcium in the blood], alkalosis and renal impairment. Symptoms can include abdominal pain, hypertension, headaches and tissue calcification. The condition has been reported in a small number of subjects taking calcium-containing medication. Previously, MAS was more common in males taking absorbable alkali and milk, but is now more common in females taking calcium-containing medication Doses up to 1,500 mg/day supplemental calcium would not be expected to result in any adverse effect, but higher doses could result in adverse gastrointestinal symptoms in a few people. An estimate for total calcium intakes has not been made as the effect is related to calcium in supplemental doses.[1]

A July 2011 article in The American Journal of Clinical Nutrition examined information from the Women’s Health Initiative randomized clinical trial and stated that patients taking calcium carbonate plus vitamin D showed an increase in the incidence of self-reported urinary tract stones. However, according to the article, the occurrence in urinary tract stones was small between the groups and less than 10 percent of the women were hospitalized. [2]Many women take calcium supplements that are available over the counter and should be aware of this possible risk.

In March 2013, Prescrire International published an article regarding calcium supplements and the risk of cardiovascular events. Some of the data presented in the article showed an increased cardiovascular risk observed in patients taking calcium supplements, while other data showed no increased cardiovascular risk in such patients.  Based on these conflicting results, calcium supplementation should be used with caution.[3]

Calcium for the prevention of osteoporosis

Many people, particularly women, take calcium supplements in the hope that it will decrease their risk of getting osteoporosis. While it has been shown that a diet containing adequate calcium can prevent high blood pressure, taking supplements to prevent osteoporosis is controversial. If you want to reduce your risk of osteoporosis, try quitting smoking, drinking alcohol in moderation if at all and doing weight-bearing exercise such as walking, aerobics, jogging, dancing, tennis or biking (although biking is less beneficial than the other listed activities).

Before buying a calcium supplement

If you decide to take a calcium supplement, some cautions are in order. You should not take calcium supplements that contain bonemeal or dolomite. The Food and Drug Administration reported that these ingredients might contain lead in amounts that could present a risk to older adults.[4] Furthermore, the body does not absorb all calcium supplements with equal ease. Unfortunately, it has not been determined which supplement is absorbed the best. One study showed that calcium citrate was best absorbed, but another showed that there was no significant difference in absorption among various types of supplements.[4],[5] Ask your pharmacist or other health professional for suggestions.

When comparing calcium supplements, you should always check how much elemental (pure) calcium they contain. Because calcium supplements contain other ingredients in addition to calcium, a 100-mg calcium supplement tablet does not contain 100 mg of calcium, and a 100-mg tablet of one supplement does not necessarily have the same amount of calcium as a 100-mg tablet of another. Calcium carbonate is 40 percent calcium, calcium gluconate is 9 percent calcium and calcium citrate is 24 percent calcium. Read the label on the container to find out the amount of elemental calcium. This is the only measurement that counts as far as your body is concerned.

A recent Journal of Parenteral and Enteral Nutrition (JPEN) systematic review revealed that, with a few possible exceptions, dietary supplements offer no benefits to well-nourished adults eating a Western diet and, in many cases, may be harmful. The results of this study reinforce Worst Pills, Best Pills News’ longstanding view that there is little evidence that dietary supplements are either safe or effective.

The study authors concluded that with the possible exception of vitamin D in elderly patients and omega-3 fatty acids in patients with a history of cardiovascular disease, no data support the widespread use of dietary supplements in the U.S. and other Western countries. Indeed, the data suggest that certain commonly used dietary supplements, including beta-carotene, vitamin A and vitamin E, may be harmful. We agree.[6]