Vitamin D is best known for helping the body build and maintain strong bones. But a large clinical trial suggests this common vitamin may also help protect tiny structures inside our cells that are linked to aging.
Researchers found that people who took vitamin D3 every day had less shortening of their telomeres over four years. Telomeres are protective caps found at the ends of chromosomes, which carry our genetic information.
A simple way to picture telomeres is to think of the plastic tips on shoelaces. Those tips help stop shoelaces from fraying, while telomeres help protect chromosomes from damage when cells divide.
Telomeres naturally become shorter as people grow older. When they become very short, cells may no longer work or divide normally, and shorter telomeres have been linked to inflammation and several diseases that become more common with age.
The new findings come from VITAL, a large randomized clinical trial involving more than 25,000 adults in the United States. A smaller group of 1,054 participants took part in this study of telomere length.
The group included women aged 55 and older and men aged 50 and older. Researchers measured telomeres in white blood cells at the beginning of the study and again after two and four years.
Some participants were assigned to take 2,000 international units, or IU, of vitamin D3 each day, while others received a placebo with no vitamin D. The researchers also studied a daily one-gram omega-3 supplement to see whether it had a similar effect.
After four years, the vitamin D group had lost less telomere length than the placebo group. The researchers estimated that the difference was similar to preventing almost three years of the telomere shortening that would normally occur with aging during that period.
Omega-3 supplements, however, did not produce a significant difference in telomere length. This suggests the result was specific to vitamin D in this part of the VITAL study rather than a general effect of taking supplements.
Dr. JoAnn Manson of Brigham and Women’s Hospital, a principal investigator of VITAL and a co-author of the study, said it was the first large, long-term randomized trial to show that vitamin D supplementation could preserve telomere length.
First author Dr. Haidong Zhu, a molecular geneticist at the Medical College of Georgia at Augusta University, said the findings suggest vitamin D may slow one part of aging at the level of cells. However, preserving telomeres does not mean that vitamin D has been proven to make people live longer or stop aging.
Scientists still need to understand why vitamin D appears to have this effect and whether the change in telomeres leads to meaningful improvements in health.
Earlier VITAL research has also linked vitamin D supplementation with lower inflammation and reduced risks of some outcomes, including autoimmune disease and advanced cancer, but its benefits can vary depending on the condition being studied.
Vitamin D can be obtained from sunlight, some foods and supplements, and the body needs it for bones, muscles and normal immune function. People should not assume that more is always better, because very high doses can be harmful and individual needs differ.
The research was published in The American Journal of Clinical Nutrition. The study adds an intriguing new clue to the question of how vitamin D may influence healthy aging, while leaving an important question for future research: whether protecting telomeres ultimately helps people stay healthier as they grow older.
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