The study, published inThe BMJ,examined 52 randomized controlled trials covering a total of 75,454 participants. In their introduction, the researchers noted that previous studies of this kind have been inconclusive: “Interpretation of these review is difficult because they include trials of vitamin D administered with calcium, which has been associated with uncommon but important side effects (e.g., cardiovascular events.) Additionally, these reviews lack sufficient detail, and trial sequential analysis showed that the pooled sample size failed to meet the optimum size.” The researchers were looking mainly for all-cause mortality outcomes, although they also looked at cancer, cardiovascular, and cerebrovascular mortality.
The researchers discovered that all-cause mortality was unaffected by vitamin D—but that all-cause mortality was significantly lower among trials with vitamin D3 supplementation than in trials with vitamin D2 supplementation. Those receiving vitamin D3 also saw a 16% reduction in cancer risk—although those receiving vitamin D2 did not. Neither forms reduced the risk of cardiovascular mortality or cerebrovascular mortality.
Related: Study: Curcumin, Resveratrol Possible Anti-Cancer Compounds Study: Vitamin D Supplementation Improves Babies’ Growth Vitamin D of No Use to Those Over 70? Experts Clarify the ResearchThe researchers concluded by noting that benefits were seen in trials with a follow-up of more than three years, suggesting that supplementation with vitamin D3 for at least three years should be considered. They added that other large randomized controlled trials are necessary.
Andrea Wong, Ph.D., VP of scientific and regulatory affairs at the Council for Responsible Nutrition, wrote in a media statement: “Scientific evidence demonstrating the benefits of vitamin D continues to grow, and this new research is no exception. Cancer is complex and multifactorial. Taking a long-term, comprehensive approach in consultation with a healthcare practitioner is what contributes the most to disease prevention. Optimal nutrition is only one component of many.
“Everyone, at any life stage, has a nutritional need for vitamin D,” Dr. Wong continues. “It is an essential nutrient, critical to overall health, and yet most people do not get enough, which is why the most recent Dietary Guidelines identified vitamin D as a nutrient of public health concern. Taking vitamin D supplements is a safe and appropriate way to achieve healthy levels, especially because vitamin D is not easily obtained through food alone. CRN encourages consumers to have their serum vitamin D levels checked, and to consult with their doctor or other healthcare practitioner about the role supplementation plays in their overall health and wellness regimen.”