Supplements and Vitamin D: Science-Backed Ways to Slow Ageing and Reduce Dementia Risk

Vitamin D supplements may help slow biological aging by preserving telomere length, according to a major new study published in The American Journal of Clinical Nutrition.

Researchers analyzed data from the VITamin D and OmegA-3 TriaL (VITAL), a large-scale randomized controlled trial involving nearly 26,000 participants over five years. In a sub-study of more than 900 individuals, those who took 2,000 IU of vitamin D3 daily showed significantly slower telomere shortening compared to the placebo group. Over four years, the vitamin D group lost an average of 140 fewer base pairs of DNA from their telomeres.

Based on prior research linking telomere length to biological aging, this difference could equate to up to three years of slowed aging, the study authors noted. Telomeres, which are protective DNA caps at the ends of chromosomes, naturally shorten with each cell division and are associated with increased risk of age-related diseases such as vascular dementia, type 2 diabetes, and cancer.

The findings support a promising role for vitamin D in countering biological aging pathways. “VITAL is the first large-scale and long-term randomized trial to show that vitamin D supplements protect telomeres and preserve telomere length,” said JoAnn Manson, principal investigator of VITAL and chief of the Division of Preventive Medicine at Harvard-affiliated Brigham and Women’s Hospital. She added that the trial had previously shown benefits of vitamin D in reducing inflammation and lowering risks of selected chronic diseases of aging, including advanced cancer and autoimmune disease.

Separate research also suggests vitamin D may help reduce dementia risk. A study of over 12,000 older adults found that those taking vitamin D supplements were 40 percent less likely to develop dementia over a 10-year period compared to non-users. The protective effect was particularly pronounced in older women, though men also experienced reduced risk. The benefit was observed regardless of whether participants took vitamin D2, vitamin D3, or combinations with calcium.

However, the dementia-related benefits appeared weaker in individuals with mild cognitive impairment or those carrying the APOE-e4 gene, a known genetic risk factor for Alzheimer’s disease. Researchers from the University of Calgary and the University of Exeter, who conducted the dementia study, noted that maintaining adequate vitamin D levels may play a role in helping to ward off Alzheimer’s disease, the most common form of dementia.

While these findings are promising, experts caution that more research is needed to confirm causality and determine optimal dosing for aging-related outcomes. The VITAL trial was designed to assess cancer and cardiovascular disease prevention, and the telomere and dementia analyses represent secondary investigations. Researchers emphasize that results should be replicated in other populations before clinical recommendations can be made.

For now, health authorities continue to recommend maintaining sufficient vitamin D levels through diet, sunlight exposure, and supplementation when necessary, particularly for older adults at risk of deficiency. Individuals considering vitamin D supplements for longevity or cognitive health should consult with a healthcare provider to assess their personal needs and avoid excessive intake.