There is increasing evidence for the presence of vitamin D, its receptor (VDR), and enzymes that activate vitamin D (change its chemical structure so it becomes biologically active in cells) in brain cells (neurons), brain supporting cells (glial cells, which outnumber neurons 10:1), spinal neurons and peripheral nerves in the arms and legs. These findings support roles for vitamin D in nervous system development and function. Such observations initiated a significant paradigm shift from vitamin D as the hormone that increased the absorption of calcium from the intestines to a hormone with systemic (throughout the entire body) actions.
On the microscopic scale, vitamin D is able to modulate and change the structure of neurons, their release and uptake of a diverse array of neurotransmitters (chemicals that enable neurons to communicate with each other), and how they carry out many daily functions. VDRs have been identified in the cerebral cortex, the cerebellum (balance center), and most interestingly of all, the limbic system (center of emotional processing). It has been recognized for many years that vitamin D deficiency is accompanied by irritability, anxiety and depression. Because it plays a central role in the regulation of seasonal rhythms, vitamin D deficiency has been linked to the incidence of SAD (Seasonal Affective Disorder). This is in keeping with its well known mood-elevating effects.
Mounting clinical evidence reveals a potentially important role for vitamin D in the aging brain. As we age, dietary consumption of vitamin D and sun exposure are restricted and may lead to profound insufficiencies in serum vitamin D levels in the elderly. These have been associated with well-documented behavioral and cognitive declines. In line with such observations are animal data that reveal serotonin-elevating effects of a vitamin D rich diet. Serotonin is the feel good chemical that the group of anti-depressants including Zoloft, Prozac and Paxil elevate.
The region of the brain called the hippocampus is the center of memory function. As it ages, so do our memories. Recent reports support the role for vitamin D as a potent anti-inflammatory agent in rat hippocampi. Another study demonstrated that vitamin D supplementation in animals slowed the development of biomarkers of aging in the hippocampus. Given the important role of the hippocampus in cognitive information processing, it is not surprising that vitamin D status influences the development of age-related mental functioning.
Global vitamin D deficiency is on the rise, not only in the elderly, but in the young and middle-aged as well. Experts in vitamin D metabolism and preventative medicine have published studies demonstrating the safety of daily amounts of vitamin D in the 4000 to 5000 IU range. The current recommended daily amount is in the 400 IU range. It is clear that this level is woefully inadequate. Because vitamin D is inexpensive and easily produced, there is no reason to permit such deficiencies, and their associated diseases, to exist!