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 James McNabb, M.D., C.N.S. |
More on Vitamin D
It was discovered in the twenties that rickets, a disease of weak bones in children, was caused by lack of vitamin D. Vitamin D appeared to cause bones to strengthen. In the next few decades, enough was learned about vitamin D that the chemical industry was able to produce large quantities of it, and a synthetic vitamin D (known as D-2) was eventually added to milk in the fifties for the prevention of childhood rickets. While the major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus, we are beginning to learn that this interesting vitamin has important functions in cancer prevention and in modulating autoimmune diseases.
We get vitamin D in two different ways. We can manufacture vitamin D ourselves through sun exposure to our skin, in response to ultraviolet light. Vitamin D is then sent to the liver, where it is converted to an intermediate form, and then finally to the kidney where it is converted to its active form, D-3. Vitamin D is also obtainable through the diet, usually in the form of fish or fish oil.
Vitamin or Hormone?
The definition of a vitamin is a compound that is needed by the body but has to be imported, usually in the diet. I say usually because our intestinal bacteria manufacture several of our vitamins for us. Pantothenic acid, biotin, and vitamin K are examples. Vitamin D, by this definition, is a vitamin required in the diet in the wintertime, when low angles of sun and winter clothing prevent any sun exposure, but is not in the summer when we can expose our skin to sunshine. Many researchers believe that vitamin D should more accurately be called a hormone. We are learning vitamin D has many properties that are only recently being discovered.
It has been known that the incidence of multiple sclerosis is four times higher in Canada than in the southern United States. A significant variable between Canada and the South is the amount of sunshine available to make vitamin D in human skin. MS is virtually unknown at the equator. The presumption is that this increased skin production of vitamin D is much higher at lower latitudes.
A 2004 Harvard study of approximately 95,000 nurses showed that the nurses that took greater than 400 IU of vitamin D daily had a 41% less risk of MS over those nurses that did not supplement vitamin D. On an experimental basis, it has been known since 1997 (Hayes, et.al., 1997) that vitamin D will completely prevent experimental autoimmune encephalomyelitis in mice, a widely accepted animal model of MS.
Vitamin D and Disease
It seems that vitamin D can help with other autoimmune diseases. A study on Type I diabetes, an autoimmune disease that attacks and kills the insulin-producing cells of the pancreas, compared 30 year olds who were supplemented with vitamin D as children with those who did not and found a ten times reduction in those who had taken vitamin D. Just how vitamin D affects the immune system in this way is not known at present.
Vitamin D also has important implications in cancer. We have known since the 1990’s that incidence rates of cancer are dramatically different depending upon latitude. The mortality for breast cancer is 33 per 100,000 in the northern states while only 17-19 in the southern portion of the US. We also know that black men who migrate to Scandinavia have greatly increased rates of prostate cancer. Experimentally, vitamin D-3 has been shown to reduce the growth, as well as increase the differentiation of cultured human prostate epithelial cells in the laboratory (Tokar, 2005).
I have written in earlier newsletters that we are living in a society that preaches extensively against any sun exposure. While I do not advocate sun exposure that results in burning or damage, I do think that we should rethink the current advice that all sun exposure is bad. Autoimmune diseases and cancer are epidemic, and vitamin D through production in the skin can be a valuable assistance. In summer, I recommend full body exposure to sun, in a short enough period not to cause burning. In the winter, I recommend supplementation with Vitamin D, at least 400 IU. In a future newsletter, I will discuss the proper dosage of vitamin D.
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