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Susceptibility to disease after infection by Mycobacterium
tuberculosis (M. tuberculosis) is influenced by environmental and host
genetic factors. Vitamin D metabolism leads to activation of macrophages
and restricts the intracellular growth of M tuberculosis. This effect
may be influenced by polymorphisms at three sites in the vitamin D receptor
(VDR) gene.
There is a high prevalence of vitamin D deficiency
in Gujarati Asians living in London, a population in whom the incidence
of tuberculosis is also high. The lowest serum 25-hydroxycholecalciferol
concentrations were found in patients with active disease, and the greatest
risk of tuberculosis (nearly ten-fold higher) was associated with an undetectable
25-hydroxycholecalciferol concentration.
Analysis of vitamin D concentrations during therapy
suggests that tuberculosis itself does not lower 25-hydroxycholecalciferol
concentrations. In addition, the association between vitamin D concentrations
and active tuberculosis showed dose dependency. Although
dietary deficiency contributes to the high proportion of vitamin D deficiency
in the population, the analysis of indicates that other factors (probably
sunlight exposure) are important. The greatest
risk of tuberculosis was associated with an undetectable vitamin D concentration,
so even moderate supplementation may be useful.
Lancet Volume 355, Number 9204
19 February 2000
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