A new study that gives fresh insight into how vitamin D may affect the immune response was published in The Lancet, a leading medical journal. Tuberculosis patients who have a particular type of vitamin D receptor are very responsive to vitamin D therapy. Vitamin D hastened sputum culture conversion in people with tt genotype of the TaqI vitamin D receptor polymorphism.
Statistics revealed by the World Health Organization says that 'with 2 million new tuberculosis cases in 2009, India carries the highest tuberculosis burden in the world'. Standard treatment regimens are aimed at bringing faster sputum conversions. A diagnosis of TB is usually made if two out of three sputum sample cultures yield mycobacterium, the pathogen that causes TB. Once treatment is initiated the response is assessed based on repeated sputum cultures. There are two phases in the treatment of TB: an initial (intensive) phase and a continuation phase. An effective therapy is one that brings a sputum conversion, i.e. when the culture doesn't yield microbes anymore.
AdvertisementVitamin D was used to treat tuberculosis in the pre-antibiotic era. The metabolic end products of vitamin D have been shown to induce anti-mycobacterial immunity in vitro, i.e. in an artificial environment outside the living body. There are no clinical trials that investigate the effect of adjunctive vitamin D on sputum culture conversion.
A multicentre randomised controlled trial of adjunctive vitamin D in adults with sputum smear-positive pulmonary tuberculosis was performed in London, UK. Vitamin D occurs in two major forms: D2 and D3. D3 (cholecalciferol) is the form made in the body in response to sun exposure. Doses of 2.5 mg vitamin D3 were given to patients receiving intensive-phase treatment for pulmonary TB. Vitamin D did not significantly affect time to sputum culture conversion in the whole study population. But it was found that sputum culture conversion hastened in people with a particular genotype.
Vitamin D receptors occur in two genetic variants or polymorphisms: TaqI and FokI polymorphisms. People with theTaqI vitamin D receptor polymorphism may further exhibit a particular genetic makeup (genotype) called tt genotype. It was in the participants with tt genotype that the positive effect of vitamin D became evident.
The findings show great promise in speeding up the antibiotic treatment of TB. The DOTS strategy implemented under the Revised National Tuberculosis Control Programme (RNTCP) in India is the international standard for TB control programmes. Treatment typically lasts for 6 to 8 months. Any headway made in the medical research field for Tuberculosis will help to improve outcomes for patients. The current study is not devoid of limitation but it does raise hopes. Being in a nation with 1.96 million new cases of TB annually, every tiny speck of hope is worth.
Primary Source: The Lancet, January 6, 2010
Reference: Martineau AR, et al "High-dose vitamin D3 during intensive-phase antimicrobial treatment of pulmonary tuberculosis: a double-blind randomised controlled trial" Lancet 2010; DOI: 10.1016/S0140-6736(10)61889-2.
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