Vitamin D May Slow Aging by Protecting Telomeres

Low levels of vitamin D have been linked to most chronic diseases, from cancer to heart disease, as well as increased risk of early death.^1-4

A major new study reveals one possible reason why.

Clinical trial results published in 2025 found that four years of daily vitamin D intake significantly reduced the shortening of telomeres, the protective caps on the ends of our chromosomes.⁵

Telomere shortening is considered one of the hallmarks of cellular aging.⁶

Compared to a placebo, adults who took vitamin D3 daily for four years reduced telomere shortening to such an extent that it may have prevented the equivalent of about three years of biological aging as measured in leukocyte immune cells.⁵

By protecting telomeres, vitamin D intake may slow certain aging processes and reduce risk for diseases that plague older adults.

Telomeres and Biological Age

Chromosomes are long strands of DNA wrapped around proteins. Found in most cells, chromosomes contain genes that provide life-preserving instructions for our cells.⁷

Telomeres cap the ends of chromosomes, protecting and preserving the structure and stability of this genetic material.⁶

In youth, telomeres are long and healthy. With age, they become progressively shorter. This loss of telomeres has been linked to age-related disease and reduced longevity.^6,8

The rate of telomere shortening has been used as a marker of biological aging in research studies for years.^6,8-10 In human studies, shorter telomeres have been shown to predict a higher risk of early death.⁸

Protecting telomeres has become an important anti-aging target.

The Importance of Vitamin D

Studies have found that individuals with low vitamin D levels are more prone to age-related diseases,^11,12 while those with higher levels are at a reduced risk for many common conditions of aging, including:

• Cardiovascular diseases,¹³
• Metabolic disease,¹⁴
• Cancer,^15,16
• Dementia,¹⁷
• Osteoporosis,¹⁸ and
• Infectious disease.¹⁹

Low vitamin D status is common, especially in older adults.²⁰

While vitamin D works in many ways, cell studies have suggested that defending telomere health is one of its key roles.^5,12,21-23 A breakthrough study published in 2025 indicates that this effect applies to humans as well.

Vitamin D Prevents Telomere Shortening

An earlier observational study found that those with high vitamin D levels had a telomere age approximately five years younger than those with low D levels.²¹

And in a small clinical trial of overweight adults, the activity of an enzyme called telomerase, which may extend telomeres, increased by 19% in those who took vitamin D daily for 16 weeks. There was no change in placebo recipients.²³

A 2025 study published in The American Journal of Clinical Nutrition used data from the randomized placebo-controlled VITAL trial. This study randomized adults over age 50 to receive either 2,000 IU of vitamin D3 per day or a placebo.⁵

Over four years, 1,054 subjects had repeated blood sampling to determine the length of their telomeres in white blood cells. As expected, telomeres tended to shorten with age. But the loss of telomeres was much slower in those taking vitamin D.⁵

Telomeres consist of repeating patterns of DNA base pairs. Studies estimate that 24 to 45 base pairs of telomere length are lost per year in adults.^6,24

In this study, compared to the placebo, those receiving vitamin D lost 140 fewer base pairs, on average, over four years. The authors of this paper stated that this is roughly equivalent to three years of less aging in the vitamin D group.⁵

This is the first time this result was observed in a large, placebo-controlled clinical trial.⁵ But previous observational studies have also found that higher vitamin D levels are associated with longer telomere length.²²

Reducing Biological Aging

In the context of aging, vitamin D’s role is not limited to telomere protection.¹²

Epigenetic changes—which determine how DNA is expressed or turned “on” or “off”—represent another marker of biological age.²⁵ Among individuals of the same chronological age, lower vitamin D levels are associated with higher (older) epigenetic age.^12,26-28

Other studies show that vitamin D supplementation in deficient individuals slows this process, as measured by DNA methylation clocks.^12,26,29,30

Vitamin D intake clearly provides protection against telomere loss and other measures of biological aging.

What You Need To Know

Vitamin D’s Effect on Telomeres

• Low vitamin D levels are associated with an increased risk of early death and most age-related chronic diseases, including cancer, cardiovascular disease, and dementia.
• A study published in 2025 reveals that vitamin D3 intake prevented the contraction of telomeres, the protective end caps on our chromosomes. Telomere shortening occurs with age and predicts risk of disease and death.
• By protecting telomeres, a marker of biological age, vitamin D may slow the aging process and help reduce risk of disease.

Summary

Optimal vitamin D levels are critical for overall healthy aging.

A recent clinical study in older adults found that vitamin D3 intake significantly reduced the rate of telomere shortening, helping to slow down biological aging as measured by telomere length, and protecting genetic material.

This data and other studies provide convincing evidence that vitamin D may help slow the aging process and reduce risk for age-related chronic disease. n

If you have any questions on the scientific content of this article, please call a Life Extension Wellness Specialist at 1-866-864-3027.

Vitamin D Benefits Breast Cancer Patients

In a recent study, women receiving chemotherapy treatment for breast cancer were randomized to receive either 2,000 IU of vitamin D3 or a placebo daily.³¹

At baseline, both groups tended to have low vitamin D levels, as is often the case in cancer patients.

After six months, 24% of subjects receiving placebo had a “complete pathological response” (meaning there were no longer signs of cancer). But in those receiving vitamin D, a robust 43% of patients had a complete response.

That’s a remarkable difference. Overall, women whose vitamin D levels were over 20 ng/mL were over three times more likely to successfully respond to treatment than those with low levels.

References

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