A large study in The American Journal of Clinical Nutrition has found a possible link between taking vitamin D3 supplements and slower biological ageing. The research, part of the Vitamin D3 and Omega-3 Trial (VITAL), points to daily vitamin D3 helping to keep telomeres—the protective ends of chromosomes—intact.
These findings suggest vitamin D3 may slow cell ageing by up to three years. This adds to growing interest in how vitamin D supports health and has attracted attention from both scientists and health experts.
Telomeres: How Cells Tell Time
Telomeres act like the end caps on shoelaces, but for chromosomes. They protect our DNA during cell division and keep chromosomes from sticking together or getting damaged. Each time a cell divides, telomeres shorten a little.
Once they get too short, the cell stops dividing or dies. This is a key part of the ageing process and links to higher risks of cancer, heart disease, and type 2 diabetes as people get older.
Dr. Haidong Zhu, a molecular geneticist at the Medical College of Georgia and lead author of the study, explains that telomeres measure biological age, which can differ from the number of years someone has lived.
Telomere length shows how much stress the body’s cells have gone through and depends on both genes and lifestyle. While telomeres aren’t a perfect health marker—very long telomeres might even raise cancer risk—they are still useful for tracking ageing and disease risk.
The VITAL trial was a randomized, double-blind, placebo-controlled study. It included 25,871 American adults—women 55 and older and men 50 and older. Over five years, the study looked at the effects of vitamin D3 (2,000 IU daily) and omega-3 fatty acids (1g daily) on health, including cancer and heart health.
A smaller sub-study with 1,054 people focused on telomere length in white blood cells, measured at the start, after two years, and after four years using quantitative PCR testing.
The results showed that those taking vitamin D lost about 140 fewer DNA base pairs in their telomeres over four years than those taking a placebo. According to the scientists, this is equal to holding back nearly three years of biological ageing.
Omega-3 supplements did not have a significant effect on telomere length. Dr. JoAnn Manson, principal investigator of VITAL and head of Preventive Medicine at Brigham and Women’s Hospital, called this the first large-scale, long-term trial to show vitamin D supplements can help protect telomeres.
Vitamin D3: Sourced from Sunshine and Food
Vitamin D3 (cholecalciferol) is made by the skin when exposed to sunlight, especially ultraviolet B rays. People can also get it from foods like oily fish (salmon, mackerel), egg yolks, and fortified products such as milk and cereals.
Supplements are popular with those who do not get enough sun or vitamin D-rich foods. The body needs vitamin D for strong bones, good calcium absorption, and healthy immune function. New research hints that vitamin D may also help reduce inflammation, which is linked to ageing and disease.
The VITAL trial used a 2,000 IU daily dose, which is higher than the US recommended daily amount (600–800 IU for most adults), but still within safe limits for healthy people. Dr. Zhu says this dose is moderate and safe, but not everyone needs supplements. People who get enough sun or eat foods rich in vitamin D may already have good levels.
These findings add to earlier, smaller studies that suggested vitamin D might help keep telomeres longer, though those results were mixed. The strong design of the VITAL trial, with randomization and blinding, reduces bias and makes the results more reliable.
Earlier data from VITAL also showed benefits of vitamin D in lowering inflammation and reducing risks of advanced cancer and autoimmune disease, making telomere protection one possible reason for these effects.
Still, experts urge people not to see vitamin D as a miracle cure. Dr. Mary Armanios, head of the Telomere Center at Johns Hopkins University, points out that the difference in telomere length found in the study is within the range seen in most people and may not lead to major health changes. There are also questions about how telomere length was measured, as some specialists believe other techniques, like Flow FISH, may be more accurate.
The study had some limitations. Most participants were white and over 50, so results might not apply to younger people or those from other backgrounds. There were hints that the effect was stronger in non-white participants and in those not taking cholesterol medicine, but more research is needed to confirm this. Dr. Zhu says larger and more diverse studies will be important to better understand the long-term benefits.
Practical Advice on Supplements
Doctors remind people that vitamin D supplements can’t replace a healthy lifestyle. Dr. Manson stresses that a balanced diet and regular exercise are still key. Supplementation may help those with low vitamin D3 or high inflammation, but most people meet their needs through sunlight and food. The National Institute on Ageing highlights that older adults often have low vitamin D, so some may benefit from supplements.
Natural sources are best. Just 15–30 minutes of midday sunlight on the skin (depending on location and skin tone) or a meal with salmon or fortified dairy can give most people what they need. Too much vitamin D from supplements can cause problems like high calcium, upset stomach, and kidney issues, so it’s wise to talk to a doctor before taking large doses.
The VITAL trial opens the door to more questions about vitamin D3’s role in slowing ageing. Researchers are now looking at other signs of cellular ageing, like DNA methylation, to see if vitamin D has wider effects. Dr. Zhu says this study helps show how nutrients might impact ageing at the cell level, but more research is needed to see if these changes improve health in the long run.
For now, the findings offer hope for those wanting to age well. While vitamin D3 might not be the secret to staying young, it could play a small part in healthy ageing when combined with sunlight, a balanced diet, and an active lifestyle.
