A very impressive study was published in the May 2025 issue of the American Journal of Clinical Nutrition showing that older adults who took 2000 IU of vitamin D33 each day for four years showed significant slowing of their telomeres upon re-evaluation at the two- and four-year follow-up mark. This study, known as the VITAL Telomere Study, was a large, randomized, placebo-controlled, trial following 25,871 females age 55 and older and males fifty and older. The researchers examined, in-person, 1054 participants and were able to show that the group who were ingested 2000 IU of vitamin D per day from supplementation, exhibited significant slowing in the shortening of their white blood cell telomeres, compared to the placebo group and compared to those who ingested a fish oil -omega-3 supplement each day.

This is very impressive because telomere length is directly tied to the aging process and risk of many age-related diseases, including cancer. In other words, the faster your telomeres shorten over your lifetime the faster you tend to age and the greater is your risk of developing certain age-related diseases. Thus, slowing down the rate of telomere shortening bodes well for a slowing of the aging process and reduction in disease risk.

So, What Are Telomeres?

Telomeres can be viewed as the end-pieces of the DNA in each of our cells.  If the DNA strand in our cells were likened to a shoelace, the telomeres would be the tips of the shoelace at each end. Every time cells divide the newly formed cell usually has a telomere length that is a little shorter than its predecessor. Once you get to a critical level of telomere shortening cells become prone to changes that contribute to cardiovascular disease, cancer, dementia and osteoporosis.  So, anything that can slow the shortening of telomeres slows aging and reduces disease risk. A great review of telomeres and age-related diseases can be found in the September 27 issue of the journal Biomedicines.

On many occasions I have highlighted research showing that getting your vitamin D level into the range of 75-125 nmol/L (30-50 ng/ml) is linked to a decreased risk of many common health conditions and that for most people supplementing with 2000 IU per day of vitamin D3 enables you to achieve this desired blood level. The May 2025 study I am citing today shows us that this same level of intake (2000 IU vitamin D3 per day) appears to slow telomere shortening and thus slows aging and helps combat age-related disease risk in another unique way, by preserving more optimal telomere length in our cells.

I have included the references for this information in the text below.

References:

Zhu H et al. Vitamin D3 and marine omega-3 fatty acids supplementation and leukocyte telomere length: 4-year findings from the VITamin D and OmegA-3 Trial (VITAL) randomized controlled trial. Am J Clini Nutr. May 21, 2025. 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

Gruber H-J et al. Telomeres and Age-Related Diseases. Biomedicines. 2021;9(10(: 1335. https://pmc.ncbi.nlm.nih.gov/articles/PMC8533433/

Pludowski P et al. Vitamin D supplementation: A review of the evidence arguing for a daily dose of 2,000 IU (50 ug) of vitamin D for adults in the general population. J Nutrients, 2014;16(3): 391 https://pubmed.ncbi.nlm.nih.gov/38337676/

 

Eat Smart, Live Well, Look Great,
Dr. Meschino