Vitamin D Supplement: Harvard study claims this common supplement reverses aging: What is it and how to use it safely? |

A team of Harvard-affiliated researchers believes so. In a groundbreaking study, they found that a daily dose of vitamin D may help preserve DNA and keep people biologically younger by years. The trial, called VITAL, tracked more than 1,000 adults over four years and has just been published in the American Journal of Clinical Nutrition.

What the Harvard study found

The study tested 2,000 international units (IU) of vitamin D3 daily—about three times the recommended amount, but still within the safe upper limit of 4,000 IU. Participants taking the supplement showed significantly less DNA damage compared to those who received a placebo. Researchers measured telomeres—protective caps on chromosomes that shorten with age and are strongly linked to longevity.“VITAL is the first large-scale and long-term randomized trial to show that vitamin D supplements protect telomeres and preserve telomere length,” said Dr. JoAnn Manson, Chief of the Division of Preventive Medicine at Brigham and Women’s Hospital. She added, “This is of particular interest because VITAL had also shown benefits of vitamin D in reducing inflammation and lowering risks of selected chronic diseases of aging, such as advanced cancer and autoimmune disease.”

According to the findings, participants on vitamin D lost far less telomere length than the placebo group, preventing the equivalent of nearly three years of aging. First study author Dr. Haidong Zhu, a molecular geneticist at the Medical College of Georgia, said: “Our findings suggest that targeted vitamin D supplementation may be a promising strategy to counter a biological aging process, although further research is warranted.”

How to use vitamin D safely

Despite the promising results, experts caution against overuse. Most adults are advised to take 600–800 IU daily, while supplements commonly come in doses of 1,000–2,000 IU. Taking more than 4,000 IU per day can be harmful, leading to a dangerous buildup of calcium in the blood. This condition, called hypercalcemia, can cause nausea, vomiting, constipation, kidney stones, and even organ damage.

The Harvard researchers stress that while vitamin D shows great potential, the trial was relatively short and lacked diversity, as most participants were white. Longer-term and more inclusive studies are needed before the supplement can be recommended as an anti-aging strategy.The study was partly funded by the National Heart, Lung and Blood Institute, a division of the National Institutes of Health (NIH).