TUESDAY, Jan. 10, 2012 (HealthDay News) --Studies have shown that vitamin D is critical for bone health and could have a protective benefit for the heart, but new research suggests that too much of it could actually be harmful.
"Clearly, vitamin D is important for your heart health, especially if you have low blood levels of vitamin D. It reduces cardiovascular inflammation and atherosclerosis, and may reduce mortality, but it appears that at some point it can be too much of a good thing," study leader Dr. Muhammad Amer, an assistant professor in the division of general internal medicine at the Johns Hopkins University School of Medicine, said in a Hopkins news release.
In conducting the study, published in the Jan. 15 issue of the American Journal of Cardiology, researchers examined five years of data from a national survey of more than 15,000 adults. They found that people with a normal levels of vitamin D had lower levels of a c-reactive protein (CRP), a marker for inflammation of the heart and blood vessels.
On the other hand, when vitamin D levels rose beyond the low end of normal, CRP also increased, resulting in a greater risk for heart problems.
"The inflammation that was curtailed by vitamin D does not appear to be curtailed at higher levels of vitamin D," Amer explained.
The researchers concluded that people should be aware of the potential risks associated with taking supplements, particularly vitamin D.
"People taking vitamin D supplements need to be sure the supplements are necessary," Amer said. "Those pills could have unforeseen consequences to health even if they are not technically toxic."
It is unclear why higher levels of vitamin D are not beneficial for the heart, the researchers said.
The U.S. National Institutes of Health provides more information on vitamin D.