Although vitamin D is best known for developing strong bones, low blood levels have been linked to an increased risk of heart attacks and strokes. But recent studies found vitamin D supplements did not bolster heart health.

“Initially, there was a lot of enthusiasm for vitamin D treatment for cardiovascular disease, and this was based on observational data,” said Dr. Erin Michos, associate professor of medicine at Johns Hopkins School of Medicine in Baltimore. “The link was that individuals who have low blood levels of vitamin D have increased risk of a lot of bad things,” she said, “including increased risk of heart attacks, stroke, heart failure, and even increased risk of death.”

But associations don’t always mean causation.

In June, an analysis in JAMA Cardiology that included 21 clinical trials showed vitamin D supplements do not reduce the risk of having or dying from a heart attack or stroke. A highly publicized 2018 study called VITAL was part of that analysis. Researchers studied more than 25,000 people across the U.S. who were taking either a daily vitamin D supplement of 2,000 IUs or a placebo.