Role of vitamin A supplementation in the treatment of tuberculosis.

Vitamin A deficiency has been commonly observed in patients with tuberculosis. Low serum retinol levels return to normal after antituberculosis treatment even when no supplements are provided. The deficiency of vitamin A observed in patients with tuberculosis might have contributed to the development of tuberculous disease in them. Alternatively, deficiency could be the result of loss of appetite, poor intestinal absorption, increased urinary loss of vitamin A or acute phase reaction in TB. Vitamin A deficiency lowers immunity while vitamin A supplementation reduces morbidity and mortality, particularly from measles and diarrhoea. Vitamin A supplementation also decreases the mortality rate in HIV-infected children and delays the progression of HIV disease in infected subjects. A higher incidence of lung cancer and increased mortality have been observed in smokers after beta-carotene supplementation. Zinc deficiency is also common in tuberculosis, which may impose a secondary vitamin A deficiency. Clinical trials have shown conflicting results regarding the effect of supplementation of vitamin A, alone or with other micronutrients, on time taken to sputum conversion in patients with pulmonary tuberculosis. Supplementation with multiple micronutrients (including zinc) rather than vitamin A alone may be more beneficial in patients with tuberculosis, but clinical trials on such a combination are lacking.