Calcium is important to bone health, but most people don’t get enough of it. That’s why supplements are recommended. A recent report links calcium supplements to an increased risk of heart attack. But do these findings hold weight?

A New Zealand team recently published a meta-analysis in the British Medical Journal that raised questions about the safety of calcium supplements. Anna Kalynych, M.D., an interventional cardiologist, helps to define “meta-analysis,” a key aspect of this study. “A meta-analysis is way to pool a number of different studies to try and obtain numbers large enough to be able to formulate some sort of conclusion that you couldn’t formulate if you were just doing the individual study analyses alone,” she says.

This particular meta-analysis found about a 30 percent relative increase in the risk of heart attack in women taking the calcium supplements, but no effect on the number of strokes or on a composite risk factor, called heart attacks, strokes and deaths. “While a 30 percent increase in risk sounds staggering, it does need some explanation, because it is a relative risk,” says Dr. Kalynych.

“Essentially what it means is if you compared those taking a placebo (sugar pill) versus calcium supplements alone, there would be five extra heart attacks for every 1,000 people taking the calcium supplements, based on this meta-analysis.” However, this study does have its flaws – the patients in the study reported in the British Medical Journal appear to be taking just calcium supplements and not a combination of calcium and vitamin D supplementation.

In fact, a different meta-analysis, published five months earlier in the Annals of Internal Medicine, looked at data from 17 studies that evaluated three different things:
1) Calcium supplement use alone
2) Vitamin D supplementation use alone
3) A combination of the two 

This study found that calcium supplements alone had minimal, if any, effect on increasing cardiovascular risk, while vitamin D supplements, at moderate to high dose, appeared to protect against it.

So what conclusions should be drawn based on these conflicting accounts? For women who are at high-risk of heart disease, Dr. Kalynych and I both suggest that you not only talk to your physician, but that you try to get as much calcium as you can from your diet. If you are at risk for osteoporosis or are known to have low levels of vitamin D, then you may consider using a vitamin D supplement along with your calcium intake. Other things you can do, which are good not only for your bones, but also for your heart, include exercising on a regular basis, avoiding smoking, and avoiding an excessive amount of alcohol and/or caffeine.

UPDATE:

A new study published online last week in the British Medical Journal re-evaluates the question of whether calcium supplements increase the risk of heart attacks and strokes. Dr. Mark Boland and his colleagues from Auckland, Aberdeen, and Dartmouth Medical School had previously published an article looking at the risk women might incur if they took calcium alone (without also taking vitamin D). These authors found a slight increased risk of heart attacks in women taking calcium supplements alone.

The authors of the study went back and looked at the large database from the Women’s Health Initiative and found that there was a modest increase in the relative risk of heart attacks and strokes for those women in the Women’s Health Initiative who were started on calcium and vitamin D supplements versus those who were already on the supplements or those who were given a placebo.

What these authors report is that for those women who were assigned to begin taking calcium and vitamin D as part of the study, there was a modest 13 to 22 percent relative increased risk of cardiovascular problems (heart attacks and strokes) versus those women who were already taking the supplements before they entered the trial or those women who were given placebo.

In fact, those women who were already taking calcium and vitamin D supplements before they entered the trial had no increased risks of heart attacks. While this is confusing, what the authors believe is that those women who did begin taking the calcium supplements in the trial may have had an abrupt change in their blood calcium level that somehow may have been associated with the minimal increased risk of heart attack and stroke. It’s important to remember that the women who were in the initial Women’s Health Initiative study were older and many had ongoing risk factors for heart attacks and strokes. So what should a woman consider out of all this?

1. Clearly, most women should try to get the majority of their calcium from their diet, since it’s never been shown that consuming a diet that has a high amount of calcium-rich foods is anything but good for you.
2. If you are not able to get enough calcium in your diet or you are not able to get enough vitamin D (from sun exposure) or are deficient in vitamin D, then you should check with your doctor, because a supplement in addition to a good diet may be of benefit.
3. None of us believe that we have enough evidence now to tell women who are already taking supplementations to stop.
   
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