For over 25 years women have been told to take daily calcium supplements to prevent fractures. Now we learn that this may “modestly” increase the risk of having a heart attack. The finding came not just from one study but a meta-analysis of 11 clinical trials with a combined total of 12,000 participants; about half of whom were randomly assigned to take a placebo or more than 500 mg calcium a day. The study participants—all over the age of 60 years and mostly women—either had osteoporosis or were trying to prevent it.

The new finding is contested for several reasons that I’ll get to later. But even if the calcium-heart attack connection is never confirmed, the unsung contribution of this meta-analysis may be the spotlight it shines on the uncertain value of calcium supplements.

The new-found harm may be modest in size but so is the benefit of taking calcium supplements. Here’s how the British Medical Journal editors summarized the meta-analysis: “Given the modest benefits of calcium supplements on bone density and fracture prevention, a reassessment of the role of calcium supplements in the management of osteoporosis is warranted.” The accompanying editorial went a step further suggesting that, however modest, the heart attack increase shouldn’t be dismissed: “Given the uncertain benefits of calcium supplements, any level of risk is unwarranted.”

Let us pause for a moment here to think about those annoying Sally Field commercials for the osteoporosis drug Boniva. Next time you see one notice that she makes no claim that the drug will prevent fractures. Instead, she tells us that she has osteoporosis and the drug has stopped and reversed her bone loss. The same careful choice of words should be directed at calcium supplements. While they may improve bone density, the jury is still out when it comes to fracture prevention.

Some critics of the meta-analysis say it should be ignored entirely because the study participants were not taking vitamin D, just calcium. Today, most women following the standard osteoporosis prevention advice take both. The British Medical Journal editorialists, who clearly saw this one coming, wrote, “No conclusive data are available to show that current doses of vitamin D supplements with or without calcium supplements reduce the rates of fracture…”

The state of calcium and vitamin D effectiveness research was summed up this way in an earlier issue of the BMJ: “Conflicting evidence exists on the role of vitamin D, either alone or in combination with calcium, in reducing fractures. Some studies have shown a reduction in the risk of fractures, others have shown no effect, and one recent study found an increased risk of hip fracture.”

Sally Field aside, fracture prevention is what it’s all about, or rather what it’s supposed to be all about.

For another reaction to the heart-attack problem, I turned to the Web site of Susan Ott, MD, who specializes in osteoporosis and bone physiology. A News Flash on her Web site (see the calcium section) announces the meta-analysis and its heart-attack finding, which Dr. Ott dismisses as due to chance. The reason: Too few participants. She supplies a link to a 2006 study, which she prefers because it has three times the number of participants. Although they were taking calcium and vitamin D, they had no increased risk of heart attack.

Unfortunately, this 2006 study isn’t the best choice for defending the use of calcium and vitamin D, given the fact that the combo did not reduce the participants’ rate of hip fracture but instead increased the risk of kidney stones. (See for yourself, click here.) Elsewhere on her Web site, Dr. Ott speculates that the same 2006 study included some participants taking too much calcium (over 2,000 mg/daily). The high doses didn’t reduce fractures but just stressed the kidneys.

What to do? One possibility to consider: focus on diet and ditch the supplements until fracture-prevention is proven. But even here, the longstanding advice to increase intake of dietary calcium in adulthood appears to have no fracture-prevention advantage. (The operative word there is “increase”.) This was shown in a 12-year study of women, age 34 to 59, who did not take calcium supplements. (See “Calcium in Adulthood” click here). This 1997 study was co-authored by Dr. Diane Feskanich, Harvard Medical School, who published one more recently that clarified things further with an 18-year follow-up study of postmenopausal women.

Neither milk nor a high-calcium diet reduced their chance of having a hip fracture. But the Harvard researchers did make a case for the use of vitamin D supplements and consumption of dark fish for hip fracture prevention because American women commonly consume less than the recommended intake of vitamin D.

Addendum: Several months after this article was posted, the New York Times announced a new report from the Institute of Medicine that questioned the need for high doses of calcium and vitamin D (click here).

Maryann Napoli, Center for Medical Consumers©

Share This Article