I am not a fan of self-dosing with vitamins. From what I've seen, except for people with demonstrated deficiencies, most studies find little positive effect from vitamin supplementation. In fact, the trend seems to be to finding that they are harmful.
But I make an exception for vitamin D. There is evidence that vitamin D deficiency is not uncommon, particularly in darker-skinned people and particularly in Northern latitudes (can you say Canada?). In recent years, hiding from the sun for fear of getting skin cancer seems to have contributed to this state of affairs. There is also evidence, albeit mostly correlational, that vitamin D supplementation helps prevent disease. One of the most intriguing bits of evidence is a relation that has been demonstrated for some diseases, most recently type 1 diabetes, to latitude (e.g see http://www.physorg.com/news131866757.html ). That is, the incidence of diabetes is highest in high northern (e.g. Canada) and southern (e.g. New Zealand) latitudes, and lowest around the equator. In high latitudes, sun exposure is least, and therefore so is vitamin D synthesis in the skin. Of course, other explanations are possible, including, as one news summary reports, "Low levels of vitamin D in patients with autoimmune disease may be result, not cause, of the disease" (Science Daily, April 16/09, http://www.sciencedaily.com/releases/2009/04/090408164415.htm ). So the inverse link between vitamin D and disease is not a slam-dunk. This brings me to autism. A Scientific American review yesterday (April 24) discusses the hypothesis that vitamin D deficiency may be a cause of autism ( http://www.sciam.com/article.cfm?id=vitamin-d-and-autism). The starting point is a curious phenomenon in which Somali (a low latitude location) immigrants to Sweden and Minnesota (both high latitude locations) appear to have an incidence of autism three to four times higher than others. The speculative hypothesis is that this is because the Somalis, especially Somali women, get far less sun exposure in their new Northern homes. This could be significant during pregnancy, leading to vitamin D deficiency and predisposition to autism. If so, then vitamin D supplementation during pregnancy may reduce the incidence of autism. The Sci Amer article notes that a pilot study is underway to look at this. I would also like to know whether, as demonstrated for diabetes, autism (in general, not just for Somalis) increases with increasing latitude. As far as I know, no one has reported such a relationship. Stephen ----------------------------------------------------------------- Stephen L. Black, Ph.D. Professor of Psychology, Emeritus Bishop's University e-mail: [email protected] 2600 College St. Sherbrooke QC J1M 1Z7 Canada Subscribe to discussion list (TIPS) for the teaching of psychology at http://flightline.highline.edu/sfrantz/tips/ ----------------------------------------------------------------------- --- To make changes to your subscription contact: Bill Southerly ([email protected])
