Don’t assume that this popular mineral supplement is harmless.

Getting a little older…and worried about your bones? Pop a calcium supplement. That’s long been the message that American women and men have received from their doctors.

What’s changed: A spate of new studies suggests that calcium supplements, which now are used by nearly half of US adults, might not be as innocuous as once thought.

Troubling research finding: A report that appeared in the British Medical Journal concluded that women who took calcium supplements had about a 30% increased risk for a heart attack. Other studies have also linked calcium supplementation to cardiovascular disease in men and women.

What most people don’t realize: While some medical experts dispute these findings, a recommendation issued earlier this year by the US Preventive Services Task Force (USPSTF)—that postmenopausal women should not take calcium supplements to prevent bone fractures—signals a possible shift in medical consensus.

This recommendation, made by an expert panel that reviewed more than 100 scientific studies, also concluded that there was not enough evidence to prove that calcium supplements prevented bone fractures in healthy premenopausal women and men. In addition, the panel concluded that there was insufficient evidence to support the use of vitamin D-3 to help promote calcium absorption. (The recommendations do not apply to women or men with osteoporosis or vitamin D deficiency—for whom supplements presumably do offer more benefit than risk.)


The research has raised important questions. How much calcium is too much? Is supplemental calcium riskier than calcium in foods? So far, there are no clear answers.

A daily calcium intake that doesn’t exceed the recommended amounts (see below) has long been presumed to be safe. In fact, most studies have found that calcium is either neutral (no good or bad effects) or slightly beneficial because it promotes bone health—and heart health by increasing HDL “good” cholesterol levels and lowering blood pressure. But researchers are now investigating whether the equation changes when some or most of the calcium comes from supplements. Some experts suspect that a “flood” of calcium created by taking a supplement leads to vascular calcification, deposits of calcium on the inside of arteries that increase atherosclerosis and the risk for clots and heart attacks.

Putting the issue in context: This wouldn’t be the first time that a substance that’s healthy when consumed from foods becomes harmful when it’s taken as a supplement. A now-famous study found that smokers or former smokers who took beta-carotene supplements were more likely to get lung cancer than those who got beta-carotene only from food sources.

And what about calcium in food? When you eat calcium-rich foods, you’re getting a mixture of nutrients that includes a variety of vitamins, minerals and other substances. Some experts now theorize that our bodies are not biologically programmed to process certain single-substance supplements, such as calcium.


Calcium is necessary not only for strong bones but also for muscle contractions, a healthy heartbeat and many other functions. For adults, the recommended daily amount of calcium from food and supplements (if necessary) ranges from 1,000 mg to 1,200 mg. (The exact amount varies with age and sex.)*

An ongoing problem: Many Americans do not eat enough calcium-rich foods and take a daily supplement “for insurance.” However, it is easy to exceed the recommended daily amount because many people don’t track their calcium intakes—or they mistakenly assume that more must be better.

Best: Until there is definitive research, play it safe and get as much of your calcium as possible from your diet. Discuss the use of supplements with your doctor, and be sure to also do weight-bearing exercise (such as walking and/or running) and strength-training (including the use of hand weights and resistance machines) to keep your bones strong.

If you have osteoporosis or significant risk factors, such as a vitamin D deficiency, or your doctor OKs a calcium supplement for some other reason, take no more than 500 mg at one time—the body can’t absorb more than that, especially if you’re over age 50, take acid blockers or have an absorption disorder. Calcium citrate is the best choice for absorption.

Best Calcium-Rich Foods

For now, no one is sure if calcium supplements really pose health risks, or how big (or small) the risks may be. Most experts agree, however, that getting calcium from one’s diet is the best approach. The standard advice to eat a nutritious, balanced diet isn’t sexy, but it works. Calcium is one of the easiest nutrients to get enough of.

For example…

  • One cup of cooked curly-leaf Scotch kale has 172 mg of calcium. Other green, leafy vegetables (including beet greens, spinach, watercress and collard greens) also are good sources of calcium.
  • Yogurt is another high-calcium food. You’ll get 338 mg in a six-ounce container of plain, skim-milk yogurt—much more than plain, nonfat Greek yogurt, which provides 187 mg per six-ounce container.
  • Fish is among the healthiest ways to get more calcium because it also provides heart-healthy omega-3 fatty acids. For example, a 3.75-ounce can of sardines (with bones) has 351 mg of calcium…a three-ounce can of pink salmon (with bones), 181 mg.
  • Almonds contain 76 mg of calcium per ounce (about 23 nuts). Other good choices are Brazil nuts and hazelnuts.

*Recommended daily amount set by the Institute of Medicine is 1,000 mg for women ages 19 to 50 and men ages 19 to 70…and 1,200 mg for women ages 51 and older and men ages 71 and older.