A large clinical trial has found that taking a daily vitamin D supplement may help slow one of the natural processes linked to aging.
The research suggests that vitamin D may protect telomeres, which are tiny structures at the ends of chromosomes that help keep our genetic material safe every time cells divide.
Telomeres work like the plastic tips on the ends of shoelaces. They stop chromosomes from becoming damaged, but they become shorter as people get older.
When telomeres become too short, cells no longer work as well, and this has been linked to diseases such as cancer, heart disease, diabetes, and some autoimmune conditions.
Vitamin D is already well known for supporting healthy bones and helping the immune system. Earlier research also suggested it might reduce inflammation, but scientists were not sure whether it could slow the loss of telomere length. Smaller studies gave mixed results, so stronger evidence was needed.
The new findings come from the VITAL study, one of the largest long-term randomized clinical trials of vitamin D and omega-3 supplements. The new research was published in The American Journal of Clinical Nutrition.
More than 25,000 adults in the United States took part in the VITAL study. For this analysis, researchers closely followed 1,054 women aged 55 years and older and men aged 50 years and older by measuring the length of telomeres in their white blood cells at the beginning of the study, after two years, and again after four years.
The participants who took 2,000 international units (IU) of vitamin D3 every day lost much less telomere length than those who received a placebo. The researchers estimated that this difference was similar to preventing almost three years of biological aging over the four-year study period.
The team also examined whether omega-3 fatty acid supplements could provide the same benefit. People who took one gram of omega-3 each day did not show a meaningful difference in telomere length compared with those taking a placebo.
Study co-author Dr. JoAnn Manson, principal investigator of the VITAL trial at Brigham and Women’s Hospital, said this is the first large, long-term randomized trial to show that vitamin D supplements can help protect telomeres. First author Dr. Haidong Zhu of the Medical College of Georgia at Augusta University said the results suggest vitamin D may slow part of the aging process inside cells.
The researchers said more studies are still needed to understand exactly how vitamin D protects telomeres and whether this leads to fewer age-related diseases over time. They also noted that people should speak with their healthcare provider before starting supplements because the right amount can differ from person to person.
The findings add to earlier VITAL results showing that vitamin D may reduce inflammation and lower the risk of some chronic illnesses, including advanced cancers and autoimmune diseases.
Together, these studies suggest that vitamin D may have wider health benefits than previously understood, although it is not a substitute for a healthy lifestyle or medical care.
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