Ask the Doctors: Reports suggest popular supplements not key to bone health
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Dear Doctor: If vitamin D and calcium don’t reduce the risk of bone fractures in older adults, as I recently read, is there any point in taking them?
Dear Reader: For years, the medical community has been touting calcium and vitamin D to prevent fractures; I’ve been guilty of this practice as well. Although some studies suggested that calcium and vitamin D could help prevent osteoporosis, the degree of improvement was never overwhelming. Still, we held fast to our medical dogma. Now, as you mention, a study has shown the need to look at the data without bias in order to provide more nuanced counsel to our patients.
The research, recently published in the Journal of the American Medical Association (JAMA), reviewed 33 studies — with a total of 51,145 participants — assessing the risk of fractures in people taking either calcium alone, vitamin D alone or calcium with vitamin D.
The calcium-only studies included various types of the mineral: calcium citrate, carbonate, malate and gluconate. The seven studies assessing the impact on hip fractures showed no improvement with the use of calcium. In fact, researchers found a 53 percent increase in the risk of hip fractures among people taking calcium. The findings on spinal fractures were more positive. Nine studies assessed that connection, finding a 17 percent decrease in risk with calcium use. Seven studies assessed total fracture rate, finding a 12 percent decrease in risk, but the rate was not considered statistically significant.
The studies that assessed the specific impact of vitamin D similarly failed to produce positive results. In the nine studies of vitamin D use and hip fracture, researchers found a 21 percent increase in the risk of fracture among those taking vitamin D. The studies assessing the impact on spinal fracture and total fractures simply found no benefit.
The studies assessing the impact of calcium combined with vitamin D yielded only marginally better results. Although the seven studies looking at the impact on hip fractures found no reduction in risk, the three studies looking only at spinal fractures did show a 37 percent reduction in risk. The studies that looked at total fracture rate showed a non-significant 10 percent reduction in risk.
The 33 trials varied in length from four months up to seven years. Of note, many studies conducted for longer periods were more likely to show a reduction in the risk of spinal fractures with the use of calcium or vitamin D, which may be because calcium and vitamin D are slow to improve bone density.
The JAMA study did not specifically look at people with osteoporosis. For them, calcium has been shown effective in maintaining bone density. A 1992 study of female nursing home residents (who have a higher likelihood of osteoporosis) found that calcium and vitamin D decreased the rate of hip fracture by 43 percent and the overall fracture rate by 32 percent.
So, if you have osteoporosis, I would recommend calcium and vitamin D. If you’re a healthy person without osteoporosis, calcium and vitamin D may produce a slight decrease in the risk of spinal fracture. Overall, however, there seems to be little benefit to this supplementation.
Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.