D is for Dementia – Vitamin D and Brain Health

Think of the health benefits of vitamin D, and you’ll probably think of bone strength. For decades, diseases like osteoporosis, osteopenia, and osteomalacia have been prevented and treated with adequate vitamin D intake, among other interventions. In recent years, the evidence that vitamin D affects more than just bones has mounted; cardiovascular disease, cancers, stroke, depression, and metabolic disorders have all been linked to low vitamin D levels. A new review adds cognitive decline and dementia to that list.

The authors of a new review assessed 37 studies that evaluated vitamin D concentrations and cognitive function. The studies included various populations and age groups, but most included both men and women over 65 years of age. As part of the review, the authors conducted two meta-analyses: one to compare the mean vitamin D concentration between participants with Alzheimer’s disease (AD) and controls and one to compare mean mental status scores between participants with low vitamin D levels and those with higher levels.

The authors report that participants with AD had significantly lower vitamin D concentrations and that mental status scores were higher among participants with higher vitamin D levels. The results are limited, however, because the methods of testing among the various studies were inconsistent and not standardized. And, several studies included in the analysis showed no differences at all between groups that were compared. And, since these were not interventional studies, no cause-and-effect relationships can be established.

Many factors affect vitamin D concentrations: skin pigmentation, age, genetics, sun exposure, geographic location of the participants, and time of year. Also, cognitive decline and aging may affect vitamin D levels through dietary and behavioral changes. Still, we know that vitamin D influences and regulates many body functions. In the brain, vitamin D has protective functions by regulating genes, directing nerve growth factor, controlling neurotransmitters, and clearing amyloid plaques (a hallmark of AD).

Currently, in the United States, 15 mcg of vitamin D daily is recommended for most children and adults. Vitamin D is available in few foods and supplements are available. A fat soluble vitamin, vitamin D is relatively safe, even at high doses, but muscle pain and gastrointestinal upset can result from supplementation. There is no conclusive amount of vitamin D that protects brain health.

The review, published in the journal Neurology, does not provide new information regarding brain health and vitamin D, but it does provide a comprehensive collection of evidence that vitamin D is, at the very least, associated with a healthy brain. Interventional studies are needed to determine just how much vitamin D guarantees a better brain. For now, most Americans would do well to take a multivitamin containing a variety of essential nutrients and maintain a healthy, balanced diet, while still remembering that no vitamin or supplement is a magic bullet for a healthy body and brain.

References

Balion C, Griffith LE, Strifler L, Henderson M, Patterson C, Heckman G, Llewellyn DJ, & Raina P (2012). Vitamin D, cognition, and dementia: A systematic review and meta-analysis. Neurology, 79 (13), 1397-405 PMID: 23008220

Hansen AL, Dahl L, Bakke L, & Thayer JF (2011). Vitamin D and executive function: a preliminary report. Perceptual and motor skills, 113 (2), 677-85 PMID: 22185082

Lu’o'ng KV, & Nguyên LT (2011). The beneficial role of vitamin D in Alzheimer’s disease. American journal of Alzheimer’s disease and other dementias, 26 (7), 511-20 PMID: 22202127

Soni M, Kos K, Lang IA, Jones K, Melzer D, & Llewellyn DJ (2012). Vitamin D and cognitive function. Scandinavian journal of clinical and laboratory investigation. Supplementum, 243, 79-82 PMID: 22536767

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