Benefits of calcium supplements called into question

04/15/2013 12:49 PM

08/08/2014 10:16 AM

Americans seem to think that every health problem can be solved with a pill. And certainly many are, especially infectious diseases that succumb to antibiotics, antifungals and, increasingly, antivirals.

But that leaves a medical dictionary full of ailments that continue to plague people despite the best efforts of Big Pharma. Most are chronic health problems related to how Americans live, especially what we eat and drink, and how we move or don’t move.

Osteoporosis is one of these increasingly prevalent and costly conditions. Although there are drugs to stanch the loss of bone and the debilitating fractures that often result, the remedies are costly, difficult to administer and sometimes have side effects that can be worse than the disease they are meant to counter.

This makes prevention the preferred and more cost-effective option. Efforts to prevent bone disease have focused on a pill, namely supplements of calcium, the mineral responsible for creating bone in youth that must be maintained throughout adult life.

But as with many other pills once regarded as innocuous, the safety and efficacy of calcium supplements in preventing bone loss is being called into question.

In February, the U.S. Preventive Services Task Force recommended that postmenopausal women refrain from taking supplemental calcium and vitamin D. After reviewing more than 135 studies, the task force said there was little evidence these supplements prevent fractures in healthy women.

Moreover, several studies have linked calcium supplements to an increased risk of heart attacks and death from cardiovascular disease. Others have found no effect, depending on the population studied and when calcium supplementation was begun.

The resulting controversy has left countless people, especially postmenopausal women, wondering whether they should be taking calcium. Given the conditional evidence currently available, the answer is not likely to be greeted enthusiastically by anyone other than dairy farmers.

The one indisputable fact is that the safest and probably the most effective source of calcium for strong bones and overall health is diet, not supplements. But few American adults, and a decreasing proportion of children and teenagers, consume enough dairy foods to get the recommended intakes of this essential mineral.

Milk consumption has taken a steady nose-dive in the past four decades, largely supplanted by sugared soft drinks that are now under fire as major contributors to obesity and Type 2 diabetes. Beyond age 20, when bone loss can begin to overtake bone formation, the typical man and woman in this country consumes less than 1 cup of milk a day. Likewise for teenage girls, who should be striving to maximize bone formation so that there is more in reserve when bone loss begins.

Yogurt, which ounce for ounce is an even better source of calcium than fluid milk, has achieved unprecedented popularity in recent years, but few consume it more than once a day. The only other notable calcium-rich foods are tofu (when prepared with calcium); calcium-fortified orange juice, soy milk and rice milk; canned salmon and sardines (but only if you eat the bones); almonds; kale; and broccoli. But few people consume enough of these foods to obtain the calcium they need.

Calcium was long thought to protect the cardiovascular system. It helps to lower blood pressure and the risk of hypertension, a major contributor to heart disease. The Iowa Women’s Health Study linked higher calcium intake in postmenopausal women to a reduced risk of heart disease deaths, though other long-term studies did not find such an association.

Controversy over calcium supplements arose when a combined analysis of 15 studies by Mark J. Bolland of the University of Auckland found that when calcium was taken without vitamin D (which enhances calcium absorption), the supplements increased the risk of heart attack by about 30 percent.

Bolland then reanalyzed data from the Women’s Health Initiative and found a 24 percent increased risk of heart attack among women who took calcium with or without vitamin D. In this case, the increased risk occurred only among those women assigned to take supplemental calcium who had not already been taking it when the study began.

Yet last December, in a report published online in Osteoporosis International, a team at the Fred Hutchinson Cancer Research Center in Seattle reported that among 36,282 postmenopausal women participating in the Women’s Health Initiative, those taking 1,000-milligram supplements of calcium and 400 international units of vitamin D experienced a 35 percent reduced risk of hip fracture and no increase in heart attacks during a seven-year follow-up.

In February, yet another study, published online in JAMA Internal Medicine, found that among 388,229 men and women initially ages 50 to 71 and followed for an average of 12 years, supplemental calcium raised the risk of cardiovascular death by 20 percent among men – but not women. The increased risk was observed only among smokers.

Adding to these confusing results is the fact that none of the studies was specifically designed to assess the effects of calcium supplements on the chances of suffering a heart attack or stroke. This can cause unexpected aberrations in research findings.

One possible explanation for a link, the JAMA researchers said, is that a bolus of calcium that enters the bloodstream through a supplement, but not gradually through dietary sources, can result in calcium deposits in arteries. Indeed, this is a known complication among patients with advanced kidney disease who take calcium supplements.

All the researchers agree that, given the widespread use of supplemental calcium, better studies are needed to clarify possible risks and benefits and to whom they may apply.

Until such information is available, consumers seeking to preserve their bones would be wise to rely primarily on dietary sources of the mineral and to pursue regular weight-bearing or strength-building exercises, or both. Walking, running, weight lifting and working out on resistance machines is unquestionably effective and safe for most adults, if done properly.

Furthermore, the National Osteoporosis Foundation maintains that the findings of current studies and advice about supplements should “not apply to women with osteoporosis or broken bones after age 50 or those with significant risk factors for fracture.” For them, the benefits of calcium supplements are likely to far outweigh any risks.

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