Vitamin D , often referred to as the "sunshine vitamin," plays a crucial role in numerous bodily functions, including calcium homeostasis and bone health. In recent years, studies have increasingly explored its potential role in the prevention and treatment of dementia. Dementia is a progressive neurodegenerative disease characterized by a loss of memory, language skills, and other cognitive functions. Millions of people worldwide are affected, and the search for effective prevention and treatment options is a central concern of medical research. 

Vitamin D and brain health  

Vitamin D receptors are distributed throughout the brain, particularly in areas important for cognitive function and memory. Preclinical studies have shown that vitamin D has a neuroprotective effect by modulating anti-inflammatory and antioxidant pathways and promoting neuroplasticity. Epidemiological studies have also shown an association between low vitamin D levels and an increased risk of cognitive impairment and dementia.  

Studies have shown that individuals with vitamin D deficiency had a higher risk of developing dementia compared to individuals with adequate vitamin D levels. The hypothesis is that vitamin D exerts neuroprotective effects by regulating enzymes in the brain involved in the pathogenesis of Alzheimer's disease, the most common form of dementia.  

Mechanisms of action  

These findings support the hypothesis that vitamin D not only plays a key role in bone health but is also crucial for maintaining cognitive functions. 

Nutrition and supplementation  

Given the potential link between vitamin D and dementia, adequate vitamin D intake is crucial. The main sources of vitamin D are sunlight exposure, food, and supplements. In regions with low sunlight exposure or in individuals who spend little time outdoors, dietary vitamin D intake can often be inadequate.  

Foods naturally rich in vitamin D include fatty fish such as salmon and mackerel, fish liver oils, and, to a lesser extent, egg yolks and certain mushrooms. Many countries have also implemented vitamin D fortification programs for foods such as milk, juice, and cereals.  

For people who do not get enough vitamin D through their diet or sunlight, dietary supplements can play an important role. Recommended daily doses vary depending on age, gender and health conditions.  

New findings from the UK Biobank study  

A recently published study from the United Kingdom, conducted on 269,229 participants aged 55 to 69 years, including 52% women and 48% men, provides new insights into the association between vitamin D levels and dementia risk. Over a median follow-up of 13.6 years, based on data from the UK Biobank, the study examined how serum vitamin D status and the use of vitamin D supplements (alone or as part of a multivitamin) are associated with the risk of dementia in general, Alzheimer's disease, and vascular dementia. 

At baseline, participants' serum vitamin D levels were measured, and information on vitamin D supplement use was collected. Participants were classified into three categories according to their vitamin D status: vitamin D deficiency (<30 nmol /L or <12 ng / mL ), vitamin D insufficiency (30–49 nmol /L or 12–19 ng / mL ), and vitamin D sufficiency (≥50 nmol /L or ≥20 ng / mL ). Data were adjusted for a variety of confounding factors, including APOE ε4 status, age, gender, socioeconomic status, smoking habits, alcohol consumption, physical activity, diet quality, time spent outdoors, BMI, disease status, and cardiometabolic biomarkers.  

The study results showed that, compared to participants with adequate vitamin D levels, the risk of developing dementia was 11% higher in participants with vitamin D insufficiency and 25% higher in those with vitamin D deficiency. Similar patterns were observed for specific types of dementia: The risk of Alzheimer's disease was increased by 10% in those with vitamin D insufficiency and 19% in those with vitamin D deficiency; the risk of vascular dementia increased by 15% in those with vitamin D insufficiency and 24% in those with deficiency.