Last week’s New England Journal of Medicine article publishing the results of a large National Institutes of Health (NIH) study on the effects of calcium and vitamin D supplements on risk of bone fracture and the risk of colon cancer has generated much media attention. The results were disappointing to some, but I believe that they help make our expectations of calcium and vitamin D more realistic.

You can review the results of the study in this NIH news release.

The result on colon cancer prevention is quite clear: calcium and vitamin D has no effect on the incidence of colon cancer.

The result on fracture prevention is more complex. (The details are in the review linked above.) Overall, there was no statistically significant difference between fracture rates in women taking calcium and vitamin D and women taking placebo. The problem is that many of the women had stopped taking the supplements by the end of the study. Women who were still taking the supplements, as well as women over 60, did have fewer fractures than women taking placebo. There was also a small but significant increase in the incidence of kidney stones in the women taking the supplements. Joan McGowan, PhD, who was a coauthor of the paper, summarizes the results well.

“If we look at all the findings together,” said McGowan,”for every 10,000 women treated for one year, two hip fractures would be prevented and five cases of kidney stones would be caused. The number of hip fractures prevented would climb to four for compliant patients and six for women over 60. Since hip fractures are considered to be more serious than kidney stones, on balance, the public health benefit of the supplements outweighs the risks.”

So I’m still recommending calcium and vitamin D supplements for my post-menopausal patients. My patients and I just have to understand that the benefit we’re expecting is smaller than we thought.