Could vitamin D help add years to your life? Researchers are still working to answer that question, with a new study providing evidence that vitamin D supplements may protect against a key driver of cellular aging and age-related diseases.
Published this month in The American Journal of Clinical Nutrition, results from a randomized trial involving more than 1,000 adults ages 50 and older showed that daily doses of vitamin D helped preserve telomeres — protective caps at the ends of chromosomes that shorten during aging and are linked to the development of certain diseases.
“In terms of telomere shortening, the effect was similar to saving about three years of aging,” says principal trial investigator JoAnn Manson, MD, MPH, DrPH, professor of medicine at Harvard Medical School and chief of the division of preventive medicine at Brigham and Women’s Hospital in Boston.
Dr. Manson notes that this latest analysis is part of a larger VITamin D and OmegA-3 TriaL (VITAL) trial, which has already shown the benefits of vitamin D in reducing inflammation and lowering risks of certain chronic diseases of aging, such as advanced cancer and autoimmune disease.
Why Preventing Certain DNA Changes Helps Slow Aging
Telomeres are like the tiny plastic caps at the end of shoelaces that prevent fraying, according to Manson. In the body, telomeres keep chromosomes from deteriorating when cells divide to make new cells with precisely the same genetic material.
Every time cells divide, telomeres get a little shorter and don’t protect chromosomes as well. When telomeres get too short, the resulting DNA damage can lead to cell death.
The scientists conducting this research were interested in looking at vitamin D and omega-3 fatty acids, as previous studies had suggested that supplementation with these nutrients may help telomeres stay intact.
What Did the Study Find?
For the study, researchers divided the subjects into four groups, with one group receiving 2,000 international units (IU) of vitamin D3 (a common form of D supplement) and 1 gram of omega-3 fatty acid per day. The other groups received either vitamin D and a placebo, omega-3 and a placebo, or two placebos.
The researchers measured telomere length in white blood cell samples taken from participants at study start, then two years and four years later.
The investigators found that vitamin D3 supplements significantly reduced telomere shortening over four years, preventing the equivalent of nearly three years of aging compared with placebo.
Omega-3 fatty acid supplements had no significant effect on telomere length throughout follow-up. This doesn’t mean that omega-3s have no benefit, according to Manson, who notes that prior research has associated these nutrients with cardiovascular disease prevention and reduction in heart attacks and stroke.
Getting More Vitamin D Into Your Life
The National Academy of Medicine recommends a daily intake of 600 IU of vitamin D (mostly from foods) for people ages 1 to 70 and 800 IU for adults ages 71 and older.
While the dosage of 2,000 IU is much higher than the recommendation, the researchers chose this amount for this trial because previous research demonstrated that taking this quantity was linked to a lower risk of chronic disease, and no side effects or safety issues were associated with this level.
Manson warns, however, that excessive amounts of vitamin D can lead to a higher calcium level in blood and urine, and some calcification may occur in the blood vessels and in the soft tissue. Mega doses can also cause certain toxicities.
She also stresses that vitamin D is not a cure-all.
“Taking a pill or a dietary supplement will never be a substitute for a healthy diet and healthy lifestyle,” she says. “It is possible to get up to the recommended dietary allowance by eating foods that are high in vitamin D.”
These foods include:
Fish (such as salmon, sardines, light tuna)
Dairy products
Milk alternatives (such as soy and almond beverages)
Mushrooms
Orange juice
Sun exposure also raises vitamin D in the body. The National Institutes of Health recommends 5 to 30 minutes of sun exposure, either daily or at least twice a week to the face, arms, hands, and legs without sunscreen usually leads to sufficient vitamin D synthesis.
Vitamin D Supplements May Help Some People More Than Others
Sue-Ellen Anderson-Haynes, RD, a spokesperson for the Academy of Nutrition and Dietetics and the founder of the women’s health resource 360 Girls & Women, calls the statistical results of the study “powerful,” but says she would also like to see future research examine how diets rich in vitamin D and sun exposure may influence telomeres.
Anderson-Haynes, who was not involved in the study, notes that certain populations may benefit more from supplementation than others. These may include older adults, those taking medicines for osteoporosis, and those with conditions that make it difficult for their bodies to absorb vitamin D, such as Crohn’s disease.
“The study really shines a light on how vitamin D can help the body,” she says. “In addition to cellular preservation, it helps in so many facets of health including the gut microbiome, mood, and sleep.”
EDITORIAL SOURCES
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Resources
Zhu H et al. Vitamin D3 and Marine ω-3 Fatty Acids Supplementation and Leukocyte Telomere Length: 4-Year Findings from the VITamin D and OmegA-3 TriaL (VITAL) Randomized Controlled Trial. The American Journal of Clinical Nutrition. May 21, 2025.
Tom Gavin joined Everyday Health as copy chief in 2022 after a lengthy stint as a freelance copy editor. He has a bachelor's degree in psychology from College of the Holy Cross.
Prior to working for Everyday Health, he wrote, edited, copyedited, and fact-checked for books, magazines, and digital content covering a range of topics, including women's health, lifestyle, recipes, restaurant reviews, travel, and more. His clients have included Frommer's, Time-Life, and Google, among others.
He lives in Brooklyn, New York, where he likes to spend his time making music, fixing too-old electronics, and having fun with his family and the dog who has taken up residence in their home.
Don Rauf has been a freelance health writer for over 12 years and his writing has been featured in HealthDay, CBS News, WebMD, U.S. News & World Report, Mental Floss, United Press International (UPI), Health, and MedicineNet. He was previously a reporter for DailyRx.com where he covered stories related to cardiology, diabetes, lung cancer, prostate cancer, erectile dysfunction, menopause, and allergies. He has interviewed doctors and pharmaceutical representatives in the U.S. and abroad.
He is a prolific writer and has written more than 50 books, including Lost America: Vanished Civilizations, Abandoned Towns, and Roadside Attractions. Rauf lives in Seattle, Washington.
