THERAPEUTIC SUBSTANCES

Antioxidants may protect against oxidative stress, which is associated with tuberculosis disease. However, direct evidence for the protective association between dietary antioxidants and tuberculosis incidence in humans has been lacking. The relation between intake of antioxidant vitamins (A, C, D, E) and individual carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein) and tuberculosis incidence was examined in the Singapore Chinese Health Study, a prospective cohort of 63,257 adults 45-74 years old enrolled during 1993-1998. Baseline intake of these antioxidants was estimated using a validated semi-quantitative food-frequency questionnaire including use of dietary supplements. After an average of 16.9 years follow-up, 1,186 incident active tuberculosis cases were identified among cohort participants. Compared to the lowest quartile, reduced active tuberculosis risk was observed for the highest quartile of vitamin A (hazard ratio = 0.71, 95% confidence interval: 0.59-0.85; P-trend < 0.01) and β-carotene (hazard ratio = 0.76, 95% confidence interval: 0.63-0.91; P-trend < 0.01), regardless of smoking status. Lower tuberculosis risk was seen for vitamin C among current smokers only. Other vitamins and carotenoids were not associated with tuberculosis risk. These results suggest vitamin C may reduce tuberculosis risk among current smokers by ameliorating oxidative stress, while vitamin A and β-carotene may have additional anti-mycobacterial properties.