The Impact of Vitamin A and Carotenoids on the Risk of Tuberculosis Progression

Background Low and deficient levels of vitamin A are common in low and middle income countries where tuberculosis burden is high. We assessed the impact of baseline levels of vitamins A and carotenoids on TB disease risk. Methods and Findings We conducted a case-control study nested within a longitudinal cohort of household contacts of pulmonary TB cases in Lima, Peru. We screened all contacts for TB disease at 2, 6, and 12 months after enrollment. We defined cases as HIV-negative household contacts with blood samples who developed TB disease at least 15 days after enrollment of the index patient. For each case, we randomly selected 4 controls from among contacts who did not develop TB disease, matching on gender and year of age. We used conditional logistic regression to estimate odds ratios (ORs) for incident TB disease by vitamin A and carotenoids levels, controlling for other nutritional and socioeconomic factors. Among 6751 HIV-negative household contacts with baseline blood samples, 192 developed secondary TB disease during follow-up. We analyzed 180 cases with viable samples and 709 matched controls. After controlling for possible confounders, we found that baseline vitamin A deficiency was associated with a 10-fold increase in risk of TB disease among household contacts (aOR 10.42; 95% CI 4.01–27.05; p < 0.001). This association was dose-dependent with stepwise increases in TB disease risk with each decreasing quartile of vitamin A level. Carotenoid levels were also inversely associated with TB risk among adolescents. Our study is limited by the one year duration of follow up and by the relatively few blood samples available from household contacts under ten years of age. Conclusions Vitamin A deficiency strongly predicted risk of incident TB disease among household contacts of TB patients. Vitamin A supplementation among individuals at high risk of TB may provide an effective means of preventing TB disease.