We often blog on what effect vitamin D has on the treatment of various diseases. For example, recently vitamin D has been found to be a promising treatment for a condition that affects up to 20% of Americans, hives.
If vitamin D has such profound effects on disease outcomes, one would hypothesize that vitamin D would also have profound effects on life expectancy. However, no one has conducted a randomized controlled trial to test this hypothesis. The study that would be needed to test any effect on mortality will never be done. It would take at least 10 years of supplementing a large group of adults with at least 5,000 IU/day. In addition, a control group would need to remain vitamin D deficient for ten years. No ethics panel at any university would approve that.
However, we can get an idea from a recent large meta-analysis of prospective cohort studies which followed about 29,000 people for an average of seven years. This meta-analysis collected subjects from eight large cohorts like NHANES 111.
Schöttker B, Jorde R, Peasey A, Thorand B, Jansen EH, Groot Ld, Streppel M, Gardiner J, Ordóñez-Mena JM, Perna L, Wilsgaard T, Rathmann W, Feskens E, Kampman E, Siganos G, Njølstad I, Mathiesen EB, Kubínová R, Pająk A, Topor-Madry R, Tamosiunas A, Hughes M, Kee F, Bobak M, Trichopoulou A, Boffetta P, Brenner H; Consortium on Health and Ageing: Network of Cohorts in Europe and the United States. Vitamin D and mortality: meta-analysis of individual participant data from a large consortium of cohort studies from Europe and the United States. BMJ. 2014 Jun 17;348:g3656.
The scientists from this study used quintiles of vitamin D levels, comparing the highest quintile to the lowest to determine if 25(OH)D levels affected mortality.
They found it did. Subjects in the highest quintile of 25(OH)D were 57% less likely to die during the mean follow up time of 7 years. Below are the risk ratios.
The researchers concluded:
“In this large consortium of eight cohort studies from Europe and the United States, the bottom 25(OH)D quintile was associated with increased all-cause and cardiovascular mortality and with cancer mortality in subjects with a history of cancer but not in subjects without a history of cancer. These relationships were compellingly consistent across countries, sexes, age groups, and seasons of blood draw…Vitamin D may play an important role in cancer prognosis.”
Remember, this benefit may be due to sun exposure, not solely vitamin D levels. The safest thing to do is get as much safe sensible sunshine as you can and take 5,000 IU/day.