Vitamin D supplementation helps in the regulation of calcium and phosphorous levels in the blood, which is essential for maintaining healthy bones and muscles. However, whether or not does vitamin D reduces the risk of cancer or cardiovascular disease (CVD) is not clear. The objective of this study is to evaluate the outcomes of vitamin D supplementation on cancer and CVD.

This nationwide, randomized, placebo-controlled trial included a total of 25,871 participants. The participants were randomly assigned in a two-by-two factorial design to vitamin D3 (cholecalciferol) at a dose of 2000 IU per day or placebo. The primary outcomes of the study were invasive cancer of any type and major CVD events, such as myocardial infarction, stroke, or CVD-related death.

The findings suggested that vitamin D supplementation was not associated with a lower risk of cancer or CVD. During the median follow-up of 5.3 years, a total of 1,617 cancer cases were diagnosed, 793 in the vitamin D group, and 824 in the cancer group. A major cardiovascular event occurred in 396 participants in the vitamin D group and 409 in the placebo group.

The research concluded that vitamin D supplementation did not lower the incidence of invasive cancer or cardiovascular events.