This blog entry will be the first in a several part series on the brain and vitamin D. Vitamin D has come to be known as the sunshine vitamin because it is almost exclusively synthesized in the skin upon sun exposure, or exposure to a limited band of UV light. Unlike most other vitamins and minerals, vitamin D is not found in many foods. Based on current estimates, prior to the migration of earlier bands of pre-humans away from the equator to higher latitudes, levels of vitamin D in their bloodstream are estimated to be about 50 ng/ml. This was largely due to prolonged sun exposure. That was the norm for our ancestors who lived near the equator and were not in the habit of covering their skin with clothing. In cities like NY or Boston, because of the tangential nature of the sun during Winter months, negligible vitamin D can be generated. For this reason and others such as dark skin color and religious beliefs requiring almost total skin coverage, more than half of all Americans are vitamin D deficient. This is the case even with the current meager basal standards. There are many published reports suggesting that the present daily recommendations for 400 - 600 International Units (IU) are woefully inadequate. Experts in the field are recommending daily amounts of 1,000 IU, 2,000 IU, or more. Under these proposed guidelines, the percentage of Vitamin D deficiency would likely be in the 75% range or higher. This observation is clearly contributing to the epidemic of osteoporosis. But there may be other implications as well.

To manifest its effect, vitamin D acts by binding to a 'receptor' that is a protein triggering molecule. When this receptor comes in contact with vitamin D, it is 'turned on' and activates certain signaling pathways responsible for carrying out the intracellular biological functions of vitamin D. The receptors for vitamin D are aptly called vitamin D receptors (VDR). Without them, vitamin D would float around in the body without being recognized. Hence, when VDRs are detected in an organ such as the intestines or bone, vitamin D clearly has a place to 'dock' and subsequently manifest its action in that tissue. Because of its major impact on calcium metabolism (by increasing the absorption of calcium from the intestinal tract, for example) it is not surprising that there are VDRs in bone and gut. What is more interesting is the identification of VDRs in the brain, an organ not generally believed to play much of a role in bone health. This finding has spurred much research investigating the possible role of Vitamin D in the brain. It has also generated many hypotheses regarding a possible role for vitamin D as being a 'neuoprotectant' nutrient.

I would like to present a discussion based upon an article by a psychiatrist, Dr. John Cannell. It is about the potential role that vitamin D, and vitamin D deficiency, may play in the etiology, or causation, of what has become a very common neurodevelopmental disorder. The prevalence of autism has increased dramatically in the past twenty years suggesting an environmental contribution. It also has a well-documented genetic basis. There is a male preponderance (4/1, M/F) and it tends to occur more frequently in African Americans. These unique observations suggest an environmental modulator of an underlying genetic contribution.

VDRs are identified throughout the brain very early in the developmental process. They have potent regulatory effects on factors responsible for formation and connectivity of nerve cells, or neurons. In 2006, it was suggested they played key roles in many other brain processes including inflammation, neurotransmission, seizure generation, and behavioral regulation.

In addition to being a hormone, vitamin D is a steroid hormone. As such it has the ability to modulate the activity of many genes. 200 human genes are currently believed to be primary targets of vitamin D. Until recent times, vitamin D was the only neurosteroid hormone generated almost exclusively in the skin. Now large numbers of pregnant women are ingesting small amounts of vitamin D orally, instead of producing large amounts in their skin. This dramatic change is novel to the human race in general, and human brain development in particular. Until modern times, especially during the past twenty years when sun-avoidance campaigns were instituted, this variance in human vitamin D physiology was unheard of.

The next article in the series will discuss the potential impact of this profound alteration.