Epidemiological studies indicate a relation between vitamin D status and autoimmune diseases, and in vitro studies demonstrate an effect of 1,25-dihydroxyvitamin D on immune activation. However, the relation between serum levels of 25-hydroxyvitamin D (25(OH)D) and the effect of vitamin D supplementation on serum levels of cytokines are not settled. In the present study interleukin (IL)-2, IL-4, IL-5, IL-10, IL-12, IL-13, IL-17, intercellular adhesion molecule-1, interferon-gamma, monocyte chemotactic protein-1, and high sensitivity C-reactive protein, were measured in 437 overweight subjects and 324 completed a one year intervention with 40,000 IU vitamin D per week (group DD), 20,000 IU vitamin D per week (group DP), or placebo (group PP). No consistent relations between serum levels of the cytokines and 25(OH)D were found at baseline. In the intervention study, there was no difference in delta values (value at end of study minus value at inclusion) between the three groups regarding the individual cytokines measured, nor was there any indication of a polarization of the T cells towards a Th2 dominant type. In conclusion, we were not able to demonstrate with certainty any significant relation between serum levels of 25(OH)D levels and a number of cytokines and markers of inflammation.
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