Vitamin D supplements slow telomere shortening, reducing biological aging by about three years in older adults.
One area of research interest is vitamin D. Several studies have found that people with higher vitamin D levels tend to have longer telomeres, however, these were mostly observational. A few small trials of vitamin D or omega-3 supplements showed some effect, but the findings were inconsistent and often too short to reveal anything about long-term aging.
To address this, researchers launched the VITAL trial – a large, long-term randomized study testing the effects of daily vitamin D3 and omega-3 supplements in older adults. The trial had already shown that vitamin D helps reduce inflammation and may lower the risk of advanced cancer and autoimmune disease, however, the team wanted to see if it also helps maintain telomeres over time.
Measuring aging at the cellular level
The sub-study followed 1,054 adults over 4 years. All participants were at least 50 years old (male) or 55 years old (female) and were generally healthy at the start of the research.
Participants were randomly assigned to take either 2,000 IU of vitamin D3 per day, 1 g of marine omega-3s, both or a placebo. Blood samples were collected at the start, and again at year two and year four. Researchers measured telomere length in white blood cells, a marker of biological aging, using a standard method called qPCR.
The Research Paper: (Paywalled)
Vitamin D3 and marine omega-3 fatty acids supplementation and leukocyte telomere length: 4-year findings from the vital randomized controlled trial.
Am J Clin Nutrit. 2025. doi: 10.1016/j.ajcnut.2025.05.003
https://www.sciencedirect.com/science/article/abs/pii/S0002916525002552?via%3Dihub