The New England Journal of Medicine recently published a study that found high-dose vitamin D supplementation provided no protective benefit with regard to risk of developing either cancer or cardiovascular disease. The long duration and size of this study provided sufficient power to examine the impact of high-dose vitamin D supplementation on these two health outcomes. Nearly 26,000 healthy study participants were randomized to receive daily doses of either 2,000 international units (IU) of vitamin D3, 1,000 milligrams (mg) of omega-3 fatty acids, vitamin D plus omega-3 fatty acids, or a placebo. After a median follow-up of roughly five years, researchers found that vitamin D supplementation did not lower the incidence of (or deaths from) cardiovascular events or invasive cancers compared to placebo. Based on these results, a high-dose vitamin D supplement is not likely to be beneficial for the prevention of cancer or cardiovascular disease.