Can vitamin D lower the risk of dementia and Alzheimer’s disease?

According to a British population study, this seems to be the case. At the same time, it’s alarming that vitamin D deficiency is such a widespread problem and that Alzheimer’s disease and other typers of dementia are on the rise, because there is most likely a connection. How does vitamin D affect brain health, and how much vitamin D do we need to help nerve cells and cells in general function optimally?

Earlier studies of vitamin D and dementia have produced conflicting results, which may easily be because the doses used have been too limited to optimize blood levels of vitamin D, or because the trials have been too short. The new population study that is published in The American Journal of Clinical Nutrition compared vitamin D supplements with blood levels of vitamin D and the rate of dementia, including Alzheimer’s and vascular dementia.
Blood levels of vitamin D measured as 25(OH)D are categorized as deficiency (lower than 30 nmol/L), insufficiency (30-50 nmol/L), and sufficiency (50 nmol/L or higher).
The researchers collected data from the UK Biobank that is a registry with comprehensive information about the health and diets of around half a million people in Great Britain. The researchers looked at 14 years of data from almost 270,000 people aged 55-69 years, where they noted their multivitamin intake, their intake of vitamin D as mono supplements, blood levels of vitamin D, and the rate of different types of dementia. The study found the following:

• 5% of the participants took vitamin D regularly
• 20% of participants took multivitamins regularly
• 34% had insufficient vitamin D levels (30-50 nmol/L)
• Vitamin D deficiency was most pronounced among those who did not take supplements
• There was less vitamin D deficiency among those who took vitamin D (7% of users) or multivitamins (10% of users)
• Participants with vitamin D deficiency (below 30 nmol/L) had a 19-25% increased risk of developing any type of dementia
• Participants with insufficient vitamin D levels (30-50 nmol/L) had a 10-15% increased risk of any type of dementia
• Regular users of vitamin D or multivitamins had a 17% and 14%, respectively, lower risk of developing any type of dementia.

Based on these results, the researchers conclude that vitamin D has the potential to prevent dementia. Their study supports a previous study that is published in Alzheimer´s & Dementia: Diagnosis, Assessment & Disease Monitoring, where it was shown that vitamin D supplementation helps prevent or delay the progression of dementia.

Vitamin D’s role in brain health and cognitive skills

Most cells in the body have vitamin D receptors (VDR) that control a host of different genes and metabolic processes. We also have vitamin D receptors in our brain, including the hippocampus, which is the part of the brain that is responsible for memory and sense of direction. Vitamin D also counteracts oxidative stress and inflammation that can cause atherosclerosis and damage nerve cells and other tissues. Vitamin D even prevents the accumulation of potentially harmful proteins in the brain, for instance beta-amyloid and tau that are involved in Alzheimer’s disease.

How much vitamin D do we need?

Our actual need for vitamin D, including vitamin D supplements, may vary a lot depending on factors like sun exposure, genetic variations that affect our vitamin D synthesis and utilization, ageing, BMI, skin color, and chronic illnesses.
The official recommendations for vitamin D are comparatively low. According to a new meta-analysis that is published in Nutrients, daily supplementation with 50 micrograms may prevent vitamin D deficiency in the majority of adults.

References:

Li-Ju Chen et al. The associations of serum vitamin D status and vitamin D supplements use with all-cause dementia, Alzheimer´s disease, and vascular dementia: a UK Biobank Based prospective cohort study. The American Journal of Clinical Nutrition. 2024

Maryam Ghahremani et al. Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status. Alzheimer´s & Dementia: Diagnosis, Assessment & Disease Monitoring, 2023

Shreeya S Navale et al. Vitamin D and brain health: an observational and Mendelian randomization study. The American Journal of Clinical Nutrition, 2022

Pawel Pludowsky et al. Vitamin D Supplementation: A review of the Evidence Arguing for a Daily Dose of 2000 International Units (50 µg) of vitamin D for adults in the General Population. Nutrients 2024