For many years, investigators have been trying to pin down the tantalizing connection between vitamin D and cancer. Epidemiological studies have found that people who live near the equator, where exposure to sunlight produces more vitamin D, have lower incidence and death rates from certain cancers. In cancer cells in the lab and in mouse models, vitamin D has also been found to slow cancer progression. But the results of randomized clinical trials in humans haven’t yielded a clear answer. The Vitamin D and Omega-3 Trial (VITAL), which concluded in 2018, found that vitamin D did not reduce overall incidence of cancer, but hinted at a decreased risk of cancer deaths. Now, in a secondary analysis of VITAL, a team led by investigators at Brigham and Women’s Hospital has narrowed in on the connection between taking vitamin D supplements and risk of metastatic or fatal cancer.
In a paper published in JAMA Network Open, the team reports that vitamin D was associated with an overall 17 percent risk reduction for advanced cancer. When the team looked at only participants with a normal body mass index (BMI), they found a 38 percent risk reduction, suggesting that body mass may influence the relationship between vitamin D and decreased risk of advanced cancer.