Vitamin D supplementation has become commonplace and appears to be the standard of care for all patients who test low for vitamin D3 on routine lab work usually done as part of a patient's annual physical exam. In a publication in JAMA Cardiology, researchers analyzed data from over 80,000 patients, enrolled in 21 separate trials looking at vitamin D supplementation given for at least one year. They found the incidence of major adverse CV events was the same in patients taking vitamin D supplements and those taking placebo. The analysis found no benefit from vitamin D supplementation on the secondary endpoints of MI, stroke, cardiovascular mortality or all-cause mortality. These data were included in the massive VITAL trial which showed that neither daily vitamin D nor omega-3-fatty acids reduce cancer or cardiovascular event risk.
These data are important as vitamin D is plentiful in many foods and being exposed to as little as 10 minutes of sunlight on a daily basis (to activate the vitamin), is usually enough to keep vitamin D levels in the normal ranges. Vitamin D toxicity is rare, so taking supplementation would unlikely cause any harm, but these studies raise the issue if taking daily doses of this vitamin is truly necessary.