The Dangerous Truth About Calcium

Date: February 1, 2017      Publication: Bottom Line Personal      Source:  Susan Levin, MS, RD, Physicians Committee for Responsible Medicine      Print:

The calcium supplements that millions of Americans take for bone health may cause serious damage to the heart. That’s the conclusion of the latest study examining the long-term risks of these supplements.

The research, published in Journal of the American Heart Association, found that people who supplement with calcium are more likely to develop arterial calcification than those who get their calcium from foods. Calcium that accumulates in the arteries can impair circulation and increase the risk for heart disease.

Yet an estimated 43% of Americans continue to supplement with calcium.



It is a fact that Americans don’t get enough calcium. Only 42% meet the estimated average daily requirement of 1,000 milligrams (mg) to 1,200 mg (the exact amount depends on age and gender). It’s a serious problem because both women and men need calcium—along with exercise, vitamin D and other ­nutrients—to prevent bone weakness and osteoporosis, a leading cause of disability and fracture-related deaths.

But supplements aren’t the answer for many people. They may slightly increase bone density, but they do little to reduce your risk for bone fractures. In a recent analysis of studies published in BMJ, researchers concluded that “evidence that calcium supplements prevent fractures is weak and inconsistent.”

The calcium that you get from food is different. It enters the body slowly and in small amounts. That’s very different from the calcium rush that you get from supplements. Also, food ­delivers a “package” that includes calcium along with dozens of other minerals and nutrients, including vitamins, proteins, fiber, amino acids and, in the case of plant foods, phytonutrients. It seems likely that our bodies benefit from nutritional complexity. You don’t get this from single-­ingredient supplements.


In the Journal of the American Heart Association study, researchers analyzed medical tests that were done on more than 2,700 people who participated in a large heart disease study. They were looking for coronary artery calcium, a heart disease risk factor.

Your calcium score (as measured by a heart CT scan) should be zero. But as people age, levels of calcium-based plaque tend to accumulate in the aorta and other ­arteries. These levels increase more in people who take calcium ­supplements.


The study found that people who supplemented with calcium were 22% more likely to have increased coronary calcium scores over a 10-year period than those who didn’t supplement. It wasn’t the amount of calcium that mattered most—it was the type. People who did not take supplements but who got a lot of calcium from foods (more than 1,400 mg daily) were 27% less likely than those who consumed the least amount of calcium from foods to have calcium scores that indicated an elevated heart risk.

Calcium deposits affect more than just the heart. A high calcium score also has been linked to increased risk for cancer including cancers of the prostate, lung, colon, breast, skin, blood, uterus and ovaries. It also has been linked to lung disease and chronic kidney disease. Example: A study published in Journal of the American College of Cardiology: Cardiovascular Imaging found that people with high coronary calcium scores were 70% more likely to develop kidney disease than those who had low scores.

Caveat: None of the calcium/heart disease studies prove conclusively that supplements increase risks. The only way to know for sure would be to conduct a randomized, double-blind clinical trial in which some participants would take supplements and others wouldn’t and then track their health over time. This type of study will probably never be done. The evidence linking calcium supplements and heart disease has become so persuasive that it would be unethical to give supplements to people who don’t need them.


We know that many Americans don’t get enough calcium in their diets and that some of these people will never try to get more in their diets. Can supplements take up the slack? Perhaps—but this makes sense only for people who absolutely need to supplement. Are you one of these people? Here’s how to know…

Get a workup first. Calcium supplements should be treated as cautiously as prescription drugs. If you’re worried about osteoporosis, talk to your doctor. Have your blood-­calcium levels tested. If you’re deficient, you might be advised to use supplements. Your doctor also should advise you on how to get more calcium in your diet and when to decide if you need supplements.


Focus on food. Some people—particularly those who have already been diagnosed with osteoporosis or who are at high risk for it—might be advised to supplement despite the possible increase in heart risks. But most people can get more than enough calcium from foods if they make a conscious effort.

Examples: One cup of low-fat yogurt has 415 mg of calcium…one cup of skim milk, 316 mg…one cup of boiled collard greens, 266 mg…one cup of white beans, 161 mg…and one cup of soy milk, 93 mg.

Consider all of the calcium in your diet. The heart risks from supplemental calcium may be proportional to the dose. You don’t want to take any more than you need to. Suppose that you’re trying to get 1,200 mg of calcium in total each day. You’re already getting some calcium from foods. Keep that in mind before choosing a calcium dose. Why take a high-dose supplement if you need only an extra 200 mg a day?

My advice: Work with a nutritionist to help you find out how much calcium you actually consume in an average day. Or use the Internet—the USDA has a good calcium-content list at and click on “Food Search.”

If you supplement, keep the doses low—your body can’t absorb more than 500 mg at a time. Calcium carbonate has the highest amount of calcium (40% calcium) compared with calcium citrate (21% calcium). But citrate may be better tolerated by those with low stomach acids, which is common among people age 50 and older.


Get vitamin D and magnesium, too. These help with absorption of calcium. Milk and many breakfast cereals are D-fortified. You also can get vitamin D from sunshine—between five and 30 minutes (depending on your skin type and age) twice a week is probably enough. Or your doctor may advise you to take a vitamin D supplement. There are different types of vitamin D (vitamin D-2, vitamin D-3). It doesn’t matter which type you take—research has shown both types to be effective.

Magnesium helps with calcium absorption, too, but you don’t need a magnesium supplement. You just need adequate magnesium in your diet. Magnesium is readily available in whole grains, nuts, seeds, beans and leafy greens.

Don’t forget to exercise. Physical activity slows the rate of bone loss in men and women with osteoporosis, and it’s among the best ways to strengthen bones before they get weak. Weight-bearing exercises (such as walking, jogging and weight-lifting) are more efficient for strengthening bones than other types of workouts (such as biking or swimming).

Recommended: 30 to 40 minutes of walking or other weight-bearing exercises most days of the week.


Source: Susan Levin, MS, RD, director of nutrition education for the Physicians Committee for Responsible Medicine, a ­Washington, DC–based nonprofit group dedicated to promoting preventive medicine, better nutrition and higher standards in research.