Vitamin D deficiency is associated with the development of dementia.

Vitamin D is a fat-soluble vitamin that plays critical roles in many physiological processes, such as blood pressure regulation, immune function, and cell growth. Poor vitamin D status is implicated in the pathogenesis of many acute and chronic diseases, including rickets, osteoporosis, multiple sclerosis, cancer, and COVID-19. Evidence from a recent study suggests that vitamin D deficiency is associated with the development of dementia.

Health experts disagree on the terminology and cutoffs used to determine vitamin D status. The Institute of Medicine (IOM) has determined that serum vitamin D concentrations less than 30 nmol/L (less than 12 ng/mL) place people “at risk for vitamin D deficiency”; those ranging from 30 to 50 nmol/L (12 to 20 ng/mL) place some populations “at risk for inadequacy”; and those of 50 nmol/L (20 ng/mL) or greater are considered “sufficient.” However, the Endocrine Society has suggested that vitamin D concentrations ranging from 52.5 to 72.5 nmol/L (21 to 29 ng/mL) define “insufficiency,” and those less than 20 ng/mL (50 nmol/L) define “deficiency.”

The study involved more than 425,000 healthy adults (ages 60 to 73 years) enrolled in the UK Biobank study who had undergone magnetic resonance imaging (MRI) studies to assess brain volumes and whose vitamin D status was known. The investigators categorized the participants according to their vitamin D status based on literature and Institute of Medicine and Endocrine Society Clinical Practice guidelines. They collected information about the participants' demographics, lifestyles, and various health factors and tracked the participants for approximately 10 years. Then they used Mendelian randomization, a research method that provides evidence of links between modifiable risk factors and disease based on genetic variants within a population, to identify causal links between vitamin D status and brain health, dementia, and stroke.

They found that lower total brain volume tended to reflect a higher rate of dementia and stroke. The participants with low vitamin D concentrations were more likely to have lower brain volumes, an increased risk for dementia and stroke, and more white matter hyperintensities (brain lesions that indicate small vessel disease) than those with high concentrations. Vitamin D conferred the greatest protection against dementia at concentrations of 50 to 74.9 nmol/L. The Mendelian randomization revealed that participants whose concentrations were less than 25 nmol/L were 54 percent more likely to develop dementia.

These findings suggest that low vitamin D increases a person’s risk for dementia. The authors suggested that as many as 17 percent of dementia cases might be prevented by achieving vitamin D sufficiency (50 nmol/L). Learn more about the beneficial health effects of vitamin D in our overview article.

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