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Vitamin D is one of the essential vitamins for the human body. There are at least 10 known types of vitamin D, the most important being vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Among them, vitamin D3 can only be synthesized by the human body under ultraviolet radiation.
Vitamin D has many benefits to the body, such as promoting calcium absorption and bone growth as we know it, as well as anti-inflammation, anti-cancer, protecting the heart and brain, preventing immune diseases, and improving mood… More importantly, vitamin D participates in the brain’s clearance of amyloid, the accumulation of which is one of the hallmarks of Alzheimer’s disease. It also helps prevent the deposition of tau protein in the brain that is associated with dementia.
Preventing or slowing down the occurrence and development of dementia is the direction of continuous efforts of medical researchers. The relationship between vitamin D and Alzheimer’s disease has been reported, but the role of vitamin D supplements as a potential intervention is not yet clear.
Recently, researchers from the University of Calgary in Canada and the University of Exeter in the United Kingdom published the latest research on Alzheimer’s & Dementia: Diagnosis, Assessment & Disease Monitoring. The results showed that taking vitamin D reduced the risk of dementia by 40%, resulting in longer dementia-free survival, suggesting vitamin D may become a potential drug for preventing dementia.
The data used in this study came from the National Alzheimer’s Coordinating Center (NACC) database (https://naccdata.org), and the final sample consisted of 12,388 participants without dementia, of whom those taking vitamin D (D+ ) group had 4,637 participants. The (D-) group had 7,751 participants who did not take vitamin D.
Results of the study over a 10-year follow-up period showed that participants taking vitamin D had a significantly higher rate of dementia-free survival than those taking vitamin D, with a 5-year survival rate of 68.4% for the D- group and 68.4% for the D+ group. The 5-year survival rate reached 83.6%. After adjusting for age, sex, education, race, cognitive diagnosis, depression, and APOE ε4 status, vitamin D consumption was associated with a 40% lower incidence of dementia compared with controls .
While vitamin D supplementation significantly reduced dementia incidence in both men and women, the sex difference was statistically significant. The data show that vitamin D affects women significantly more than men. Women who received vitamin D supplemented had a 49 percent lower risk of dementia, compared with just 26 percent for men.
APOE ε4 is the greatest risk gene for Alzheimer’s disease, and the researchers also analyzed the effect of vitamin D in people who carried the gene. The study found that although the incidence of dementia was significantly reduced in both APOE ε4 carriers and non-carriers supplemented with vitamin D, non-carriers were more affected, and APOE ε4 carriers may benefit less from vitamin D supplementation. The authors suggest that vitamin D supplementation may not fundamentally overcome the risk posed by the APOE ε4 gene.
In conclusion, vitamin D consumption was associated with a higher rate of dementia-free survival and a lower incidence of dementia over a 10-year period. In addition, research suggests that vitamin D supplementation may be more beneficial early on before cognitive decline starts.
 Maryam Ghahremani, Eric E. Smith, Hung-Yu Chen, et al. Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status, Alzheimer’s & Dementia: Diagnosis， Assessment & Disease Monitoring (2023). https://doi.org/10.1002/dad2.12404.
 Joshua P. Sutherland, BHSc Nut Med (Hons), Ang Zhou, PhD, et al. Vitamin D Deficiency Increases Mortality Risk in the UK Biobank, Annals of Internal Medicine (2022). DOI: 10.7326/M21-3324