Vitamin D helps regulate the amount of calcium and phosphate in the body, providing the nutrients needed to maintain the health of bones, teeth, and muscles. A deficiency in vitamin D can lead to reduced bone density and can contribute to osteoporosis and fractures. While the role of vitamin D in skeletal health is well-established, new research has linked vitamin D deficiency to a range of non-skeletal conditions, including cardiovascular disease, diabetes, stroke, and recently, cognitive impairment and dementia.
In this article, we will take a look at the potential effects of vitamin D deficiency on brain health, discussing its effects on the two primary components of brain health: cognitive health and mental and behavioral health.
Over the last several decades, animal studies and human studies have demonstrated a potential link between vitamin D deficiency and cognitive decline. While many cross-sectional studies have shown a strong association between low vitamin D and cognitive impairment, longitudinal studies have shown rather mixed results.
For example, a 2018 population-based longitudinal study of 1,058 adults (with a median age of 75) found that even moderately low vitamin D was associated with poorer performance in multiple domains of cognitive function. However, low vitamin D was not able to predict a 12-year cognitive decline.
On the other hand, a 2015 population-based longitudinal study of 405 elderly adults found that severe vitamin D deficiency was independently associated with future risk of mild cognitive impairment (MCI) as well as dementia. Similarly, a 2017 population-based longitudinal study of 916 adults aged 65+ found that compared to individuals with vitamin D sufficiency, those with vitamin D deficiency exhibited a faster rate of cognitive decline. Vitamin D deficiency was associated with a nearly three-fold increased risk of developing Alzheimer’s disease.
While the underlying mechanisms linking vitamin D deficiency with cognitive decline and dementia are not fully understood, several mechanisms have been proposed:
Vitamin D deficiency has been increasingly associated with several depressive disorders, though the directionality remains unclear. While vitamin D deficiency is known to be more prevalent in those with depressive disorders, some researchers believe that low vitamin D levels may increase the risk of developing depression.
Several cross-sectional studies and cohort studies have linked depression and low levels of vitamin D. In a 2020 systematic review of available literature, it was found that all included studies demonstrated that depressed subjects had lower levels of vitamin D compared to controls. They also found that those with the lowest vitamin D levels had the greatest risk of depression (odds ratio 1.31).
Proposed biological links between vitamin D and depression include:
Emerging research also suggests that vitamin D supplementation may provide therapeutic benefits for individuals with depression; however, findings have been somewhat inconsistent.
According to the Office of Dietary Supplements at the National Institutes of Health recommended that daily allowances for vitamin D are as follows:
|Age||Male(mcg, IU)||Female(mcg, IU)|
|0-12 months*||10, 400||10, 400|
|1-70 years||15, 600||15, 600|
|>70 years||20, 800||20, 800|
* Adequate intake
An estimated 41.6% of Americans have a vitamin D deficiency. Given the high prevalence, research surrounding the effects of vitamin D deficiency on brain health may have important public health implications, though further investigation is needed.
If you are looking to increase your vitamin D levels to meet the recommended daily intake, you may consider the following sources of vitamin D:
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