Results from the VITAL randomised controlled trial reveal that vitamin D supplementation helps maintain telomeres, protective caps at the ends of chromosomes that shorten during ageing and are linked to the development of certain diseases. The new report, published in The American Journal of Clinical Nutrition, is based on data from a VITAL sub-study co-led by researchers at Mass General Brigham and the Medical College of Georgia, and supports a promising role in slowing a pathway for biological ageing.

"VITAL is the first large-scale and long-term randomized trial to show that vitamin D supplements protect telomeres and preserve telomere length," said co-author JoAnn Manson, MD, principal investigator of VITAL and chief of the Division of Preventive Medicine at Brigham and Women's Hospital, a founding member of the Mass General Brigham healthcare system. "This is of particular interest because VITAL had also shown benefits of vitamin D in reducing inflammation and lowering risks of selected chronic diseases of ageing, such as advanced cancer and autoimmune disease."

Telomeres are made of repeating sequences of DNA, or base pairs, that prevent chromosome ends from degrading or fusing with other chromosomes. Telomere shortening is a natural part of ageing and is associated with an increased risk of various age-related diseases.

A few short-term, small-scale studies have suggested that vitamin D or omega-3 fatty acid supplementation may help support telomeres, but results have been inconsistent. VITAL is a randomised, double-blind, placebo-controlled trial of vitamin D3 (2,000 IU/day) and omega-3 fatty acid (1 g/day) supplementation that tracked U.S. Females aged 55 years and older and males aged 50 years and older for five years. The VITAL telomere sub-study included 1,054 of these participants, whose telomere length in white blood cells was assessed at baseline and at year 2 and year 4.

Compared with taking a placebo, taking vitamin D3 supplements significantly reduced telomere shortening over four years, preventing the equivalent of nearly three years of ageing compared with placebo. Omega-3 fatty acid supplementation had no significant effect on telomere length throughout follow-up.

"Our findings suggest that targeted vitamin D supplementation may be a promising strategy to counter a biological ageing process, although further research is warranted," said Haidong Zhu, PhD, first author of the report and a molecular geneticist at the Medical College of Georgia, Augusta University.