Jul 09
24
Is Vitamin D supplementation necessary?
We all know that the presence of vitamin D in our bodies is important for a variety of reasons notably for the absorption and utilization of calcium & phosphorus by the intestinal tract, to enable normal mineralization of the bone, reduce cancer risk and may play a role in the prevention or treatment of type 1 and type 2 diabetes, hypertension and multiple sclerosis.
The question here is what is the best source of vitamin D?
Science seems to be divided on the answer to this question especially in the area of supplementation. There are some scientists who believe that our diets are deficient in vitamin D and that supplementation is necessary. Others say that the recommended dosages for adequate vitamin D supplementation are inadequate (Michael Holick, M.D., and a group of other nutrition experts writing in the American Journal of Clinical Nutrition (March, 2007, 85(3);649-650.) Still others claim that vitamin D supplementation suppresses the immune system (Trevor Marshall, Ph.D., professor at Australia’s Murdoch University School of Biological Medicine and Biotechnology).
In the absence of a clear scientific conclusion where should we turn for the answer to the question at hand? Personally, when I am conflicted, having no clear choice I always chose to err on the side of safety and turn to the body’s built in mechanisms. The body produces vitamin D naturally when the skin is exposed to ultraviolet rays. In my opinion this is the most natural method of assuring that vitamin D is present in the body. Many studies show that most people meet their vitamin D needs through exposure to sunlight. The factors that affect UV radiation exposure and research to date on the amount of sun exposure needed to maintain adequate vitamin D levels make it difficult to provide general guidelines. It has been suggested by some vitamin D researchers, for example, that approximately 5-30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis and that the moderate use of commercial tanning beds that emit 2-6% UVB radiation is also effective. Individuals with limited sun exposure need to include good sources of vitamin D in their diet (milk or fish) or take a supplement.
It is important to note that vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D [25(OH)D], also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as clairol. For people who suffer from some kind of dysfunction of the liver or kidney further supplementation may be necessary for the body to hydroxylate the vitimin. If you do suffer from inadequate liver or kidney function and desire to optimize the way your body uses vitamin D you should consult your physician.
Conclusion: Until there is a clear consensus on weather vitamin D supplementation is beneficial or harmful I suggest letting your body produce it’s own vitamin D from sunlight as it was designed to do.
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