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