May 27, 2025 — A common daily supplement may be doing more than supporting bone health. A new study suggests vitamin D could also help slow the body’s biological aging process.
Researchers from Mass General Brigham and the Medical College of Georgia found that vitamin D supplements may reduce the rate at which telomeres—protective caps on DNA—shorten over time. Telomere shortening is associated with aging and increased risk of age-related diseases.
The findings, published in The American Journal of Clinical Nutrition, come from a four-year nationwide clinical trial involving over 1,000 U.S. adults. Participants included men over 50 and women over 55.
Vitamin D Shows Protective Effect on DNA
Study participants were randomly assigned to take either a placebo or a daily dose of vitamin D3 (2,000 IU) and omega-3 fatty acids (1 gram). Researchers measured telomere length in white blood cells at the beginning, two-year, and four-year points of the study.
The results showed that those taking vitamin D3 experienced significantly less telomere shortening than those in the placebo group. The effect was equivalent to nearly three fewer years of biological aging, researchers said.
By contrast, omega-3 supplements showed no measurable impact on telomere length.
“This is the first large-scale, long-term randomized trial to demonstrate that vitamin D may protect telomeres,” said Dr. JoAnn Manson, a co-author of the study and professor of women’s health at Harvard Medical School.
Why Telomeres Matter
Telomeres act like the plastic tips at the ends of shoelaces, preventing chromosomes from fraying or fusing. As people age, telomeres naturally shorten. Shorter telomeres have been linked to a higher risk of chronic diseases such as cancer and cardiovascular conditions.
Because of this, scientists view telomere length as a marker of “biological age,” which may provide more insight into health status than chronological age.
Earlier phases of the trial also found that vitamin D supplementation may reduce inflammation and lower the risk of conditions such as advanced cancer and autoimmune disease.
“Our findings suggest that targeted vitamin D supplementation may be a promising strategy to counter the biological aging process,” said lead author Dr. Haidong Zhu, a molecular geneticist at the Medical College of Georgia. “However, more research is needed.”
Experts Urge Caution
While the findings are promising, researchers stressed that further studies are needed to determine how vitamin D impacts various populations and whether the benefits last over longer periods.
Before starting any new supplement regimen, healthcare providers recommend speaking with a doctor to discuss appropriate dosage and potential health risks.
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