This Vitamin May Slow Biological Aging

You’ve probably heard that things like gray hair, wrinkles or brain fog are signs of aging—but deep inside your cells, a different kind of aging is happening as your telomeres slowly shrink with every passing year. Telomeres are protective caps at the ends of your DNA, and they help keep your cells stable every time they divide. Shorter telomeres have been linked to a higher risk of age-related diseases.

Now, new research offers a compelling insight into how we might help slow that biological clock.

A randomized controlled trial, published in the American Journal of Clinical Nutrition, suggests that supplementing with vitamin D3 may help preserve telomere length, potentially protecting your DNA from premature aging. The findings come from the landmark VITAL study, one of the largest and longest-running trials of its kind, and they add to the growing body of research linking vitamin D to healthy aging.

In this new study, researchers found that participants who took 2,000 IU of vitamin D3 daily had significantly less telomere shortening over four years compared to those who took a placebo. While vitamin D is already known for supporting bone health and immune function, this study suggests it could also play a role in keeping your cells—and perhaps even your entire body—healthier for longer.

How Was This Study Conducted?

This research was part of the VITAL trial, a large, long-term randomized, double-blind, placebo-controlled study based in the United States. VITAL originally followed over 25,000 adults—women aged 55 and older and men aged 50 and older—over five years to investigate the health effects of vitamin D3 and omega-3 supplements.

A subset of 1,054 participants joined a telomere sub-study. Researchers measured the length of participants’ telomeres (in white blood cells) at the start of the study, then again at years two and four. Participants were randomly assigned to receive either a daily supplement of 2,000 IU of vitamin D3, 1 gram of omega-3 fatty acids, both or a placebo.

What Did the Study Find?

Compared to those taking a placebo, participants who took 2,000 IU of vitamin D3 each day experienced significantly less telomere shortening over four years. In fact, the difference was equivalent to preventing nearly three years’ worth of biological aging.

On the other hand, omega-3 supplements did not have a measurable impact on telomere length.

“VITAL is the first large-scale and long-term randomized trial to show that vitamin D supplements protect telomeres,” said study co-author JoAnn Manson in a press release. These results align with other VITAL findings that suggest vitamin D may help reduce inflammation and lower risk for chronic conditions like advanced cancer and autoimmune disease.

While telomere shortening is a normal part of aging, accelerated shortening is linked to increased risk of age-related diseases. That’s why interventions that preserve telomere length are being studied as ways to promote healthier aging.

Like all studies, this one has its limitations. In particular, the majority of the participants were hispanic and white, which makes it difficult to generalize these findings across other racial or ethnic groups. Additionally, since this study analyzes data from another study, the researchers note that their conclusions should be considered as hypotheses more than firm conclusions.

How Does This Apply to Real Life?

Vitamin D is known to play a vital role in supporting immune health, bone strength and, according to this new research, potentially cellular aging. Yet many people aren’t getting enough of it. In fact, the Dietary Guidelines for Americans lists vitamin D as a “nutrient of concern” because so many adults fall short of the recommended intake.

Our bodies can make vitamin D when skin is exposed to sunlight—specifically, UVB rays. But if you live in a northern climate, spend most of your time indoors, use sunscreen diligently or have darker skin (which reduces vitamin D synthesis), you may not be making enough. 

And since few foods naturally contain vitamin D—though fish-liver oils, fatty fish like salmon or mackerel, mushrooms exposed to sunlight, egg yolks and liver are exceptions—it can be tough to meet your needs through food alone. That’s where supplements can come in. 

The standard recommended dietary allowance (RDA) for adults is 600 IU per day up to age 70 and 800 IU per day for those over 70. However, this study used a significantly higher dose—2,000 IU of vitamin D3 daily. If you’re considering adding a supplement to your routine, especially at doses above the RDA, it’s important to talk to a healthcare provider first. They may recommend checking your blood levels of vitamin D to guide next steps.

While more research is needed to confirm exactly who benefits most from vitamin D supplementation, this study adds to the growing evidence that getting enough of this nutrient may be a meaningful way to support healthy aging. It’s another reason to get outdoors and eat more salmon.

The Bottom Line

A new study from the VITAL trial found that taking 2,000 IU of vitamin D3 daily helped preserve telomere length over four years, potentially slowing biological aging. 

“Our findings suggest that targeted vitamin D supplementation may be a promising strategy to counter a biological aging process, although further research is warranted,” said Haidong Zhu, Ph.D., one of the study authors, in a press release.

If you’re thinking about increasing your vitamin D intake, talk with a trusted healthcare provider to find the right approach for you.