A new study published in The American Journal of Clinical Nutrition suggests that vitamin D supplementation could play a role in slowing biological aging.
The research, part of the larger VITAL trial, found that individuals who took daily vitamin D supplements over a four-year period experienced less shortening of their telomeres — the protective caps on chromosomes that naturally wear down over time.
Telomeres function much like the plastic tips on shoelaces, preventing chromosomes from fraying. As they shorten with age, the risk for various age-related diseases, including cancer and cardiovascular conditions, tends to increase. According to Dr. JoAnn Manson, lead investigator of the study and chief of the Division of Preventive Medicine at Brigham and Women’s Hospital, vitamin D supplementation appeared to preserve telomere length, potentially reducing biological aging by up to three years.
Participants in the trial were 50 years or older and randomly assigned to receive either 2,000 IU of vitamin D daily or a placebo. Their white blood cells were analyzed at baseline, year two, and year four. Researchers found that telomere shortening in the vitamin D group was significantly less than in the placebo group — comparable to just one year of biological aging, instead of four.
This study builds on previous findings from the same VITAL trial, which involved nearly 26,000 people and linked vitamin D to reduced inflammation, lower risk of autoimmune diseases, and certain cancers — all of which are connected to aging.
However, Dr. Manson cautions that while the results are promising, they do not warrant universal vitamin D supplementation for the specific purpose of slowing aging.
“Further research is needed to confirm these findings,” she said.
Factors such as appropriate dosing and who benefits most remain areas of active study.
Vitamin D can be obtained through moderate sun exposure, foods like salmon, tuna, and fortified dairy products, as well as supplements. While 1,000 to 2,000 IU per day was found to be safe in the study, the general recommended dietary allowance for adults is 600 IU, increasing to 800 IU for those over 70.
Certain groups — including individuals over 75, those with limited sun exposure, or with conditions affecting vitamin absorption — may benefit more from supplementation. However, excessive vitamin D intake can lead to toxicity, with risks such as elevated calcium levels.
Manson emphasized that supplements should complement, not replace, healthy lifestyle habits.
“It’s much easier to pop a pill than to be physically active and eat healthfully,” she said, “but those lifestyle factors are far more powerful when it comes to long-term health.”
Fortune and New York Post contributed to this report.
