MRC National Institute for Medical Research, London
Science for Health
Vitamin D deficiency associates strongly with tuberculosis in Cape Town
31 October 2011
Researchers at NIMR and in Cape Town have found that Vitamin D deficiency is extremely common in black Africans living in Cape Town, South Africa and is associated with susceptibility to tuberculosis infection. The research is published in PNAS.
South Africa has the third highest burden of tuberculosis (TB) in the world: 490,000 cases were estimated to have arisen in 2009. Active TB can arise as a consequence of reactivation of latent Mycobacterium tuberculosis (MTB) infection following compromise of the antimycobacterial immune response. HIV infection is a major cause of such immunocompromise, and the high prevalence of HIV infection in South Africa drives its TB epidemic.
Vitamin D deficiency is associated with susceptibility to tuberculosis (TB) in HIV-uninfected people in Europe, but the prevalence of vitamin D deficiency in patients with TB with and without HIV infection in subtropical Africa has not previously been reported. There is particularly good reason to investigate this question in Cape Town, South Africa, because TB incidence in Cape Town is higher than elsewhere in South Africa and the ability of sunlight to synthesize vitamin D is compromised during the winter in Cape Town.
Robert Wilkinson (pictured), from NIMR’s Division of Mycobacterial Research and the University of Cape Town, South Africa, worked with colleagues in Cape Town and London to conduct a cross-sectional study to determine whether vitamin D deficiency was associated with susceptibility to active TB in HIV-uninfected and HIV-infected black Africans in Cape Town. He also investigated whether there was evidence of seasonal variation in vitamin D status and TB notifications in this setting over an 8-year period. The team measured vitamin D levels in the serum of HIV infected and uninfected patients with tuberculosis and appropriate control subjects who did not have tuberculosis.
They found that vitamin D deficiency is highly prevalent among black African adults living in Cape Town. Vitamin D deficiency is associated with susceptibility to active TB in both HIV uninfected and infected persons, but the association is stronger in HIV-infected people. A seasonal pattern of notifications of tuberculosis occurs in Cape Town with the lowest rates in the second quarter of the year, coincident with peak vitamin D serum concentrations.
A growing body of evidence suggests that vitamin D deficiency may also impair the immune response to MTB. We have previously reported that vitamin D deficiency is associated with susceptibility to TB in London and that this association is modified by polymorphisms in the vitamin D receptor and vitamin D binding protein. Adrian Martineau has also shown that in vivo vitamin D supplementation enhances immunity to mycobacteria both in healthy people and in a genetically defined subgroup of patients with active TB. Vitamin D supplementation might be a highly cost effective, safe and simple means to reduce tuberculosis incidence. This research is of relevance to the UK because TB is more common amongst immigrants from Africa who are more likely to be HIV infected and be vitamin D deficient.
Robert Wilkinson
Original article
Reciprocal seasonal variation in vitamin D status and tuberculosis notifications in Cape Town, South Africa
Adrian R. Martineau, Shepherd Nhamoyebonde, Tolu Oni, Molebogeng X. Rangaka, Suzaan Marais, Nonzwakazi Bangani, Relebohile Tsekela, Lizl Bashe, Virginia de Azevedo, Judy Caldwell, Timothy R. Venton, Peter M. Timms, Katalin A. Wilkinson, and Robert J. Wilkinson. (2011)
Proceedings of the National Academy of Sciences, USA. Epub ahead of print. Publisher abstract.
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