The American Journal of Clinical Nutrition recently published the results of a randomized and placebo-controlled trial evaluating the effect of vitamin D on leukocyte telomere length (LTL), an established biomarker of aging. Known as the VITAL Telomere study, it was a subset of the much larger VITamin D and OmegA-3 TriaL (VITAL) trial, an ongoing trial investigating the effects of vitamin D and omega-3 fatty acid supplementation on a number of outcomes, including cancer and cardiovascular disease.
The VITAL Telomere study included over 1,000 participants with a 2x2 factorial design that allowed for the comparison of vitamin D (2,000 IU/day), omega-3 fatty acids (1 g/day), or their combined use with placebo. Telomeres were measured at baseline and again at 2 years and 4 years into the study.
Vitamin D supplementation was associated with significantly lower LTL attrition (shortening), approximately 140 base pairs by year 4, or 35 base pairs per year, compared to placebo. Omega-3 fatty acids were not found to have an effect on LTL. For context, adults are expected to have an attrition rate of between 30-40 base pairs per year, with large population studies demonstrating that longer lengths are associated with lower all-cause mortality. For example, in two Danish prospective cohort studies, a comparison of the shortest to longest deciles (a mean difference of about 1,000 base pairs) was linked to a 40% greater all-cause mortality risk. Thus, the attrition resulting from vitamin D supplementation seems quite clinically important, perhaps with a meaningful influence on biological aging.