While the importance of vitamin D for bone health is well-known, new evidence suggests that it also plays an important role in the brain. Vitamin D deficiencies are particularly widespread among older adults; estimates of the percentages of older adults in North America and Europe who are vitamin D-deficient range from 40 to 100 percent. Vitamin D can be obtained either from exposure to sunlight or through diet. The reasons for low levels of vitamin D among older adults appear to include poor diets, limited exposure to sunlight, and older adults’ skin having a reduced ability to convert sunlight into vitamin D.
In light of this common vitamin deficiency among older adults, a recent study investigated the direct impact of vitamin D on the damaging molecules associated with cognitive decline in middle to older age rats. The rats in this study were fed levels of vitamin D that were equivalent to low, typical, or high amounts of the vitamin in a human diet. This diet began when the rats were at middle age and continued for four to five months. Once this diet was completed, researchers examined whether there was any antioxidant effect on the rats’ brains. When they looked for the elevated presence of cell-damaging molecules associated with an insufficient amount of antioxidants in the brain, they found that the rats with the low vitamin D diet showed an increase in these damaging molecules, while the rats in the typical and high vitamin D groups did not show any difference in the level of these molecules. The low vitamin D group had approximately 25 percent more of these damaging molecules present than rats with either typical or high vitamin D diets. Additionally, in this study vitamin D was shown to have anti-inflammatory properties in the brain as well. Preliminary evidence from this research also shows that the rats in the low vitamin D group show impairments in learning and memory tasks, and that this performance improved with higher vitamin D.
This direct investigation into the molecular causes for damage to brain regions from low levels of vitamin D in rats helps scientists better understand why correlations between vitamin D and a higher incidence of cognitive impairment have been observed in humans. Patients with Alzheimer’s Disease have also been observed to have lower vitamin D levels, and this study also suggests that these low levels of vitamin D has likely had damaging effects on these individuals’ brains.
Keeney JTR, Förster S, Sultana R, et al. Dietary vitamin D deficiency in rats from middle to old age leads to elevated tyrosine nitration and proteomics changes in levels of key proteins in brain: implications for low vitamin D-dependent age-related cognitive decline. Free Radical Biology and Medicine (2013); 65: 324–334.