The VITAL study: vitamin D, cancer & cardiovascular risk
Vitamin D supplementation might reduce your risk for death from cancer by 25%.
Based at Harvard Medical School, JoAnn Manson and her team enrolled 25.871 participants in the VITAL study.
Participants were assigned random & double-blind to either Vitamin D3 (cholecalciferol; 2.000 IU/daily p.o.) or Vitamin D3 (placebo); results were published in The New England Journal of Medicine in 2018. Another part of the VITAL study covered supplementation marine n-3 fatty acids ("omega-3"), and results were reported separately.
After a median follow-up of 5.3 years, there was no difference in all-cause mortality between groups. But, although not specified in the pre-registered trial protocol, an exclusion of the first 24 month period after enrollment showed a significantly 25% lower rate of death from cancer with vitamin D supplementation than with placebo. But there was no difference for the incidence of cancer in this sub-group analysis. In The Harvard Gazette, Manson justifies this analysis by the latency of clinical cancer incidence and a presumable delayed beneficial effect of vitamin D substitution.
There were no significant reductions in cardiovascular events (myocardial infarction and stroke).
The possible reduction in the rate of death from cancer is in line with several other clinical studies - mainly observational in study design - as well as backed by laboratory studies, "whereby vitamin D may inhibit carcinogenesis and slow tumor progression, including promotion of cell differentiation, inhibition of cancer-cell proliferation, and antiinflammatory, immunomodulatory, proapoptotic, and antiangiogenic effects."
An additional finding in the sub-group analyses showed a pronounced reduction in cancer incidence during follow-up for participants with normal body mass index (BMI), while this effect could not be observed for participants with elevated BMI.
Vitamin D3 supplementation (2.000 IU/day) might reduce your risk for death from cancer by 25%; if you maintain normal (or low-normal) BMI, it might even benefit your risk of being diagnosed with cancer.