VEGETARIAN DIET AS A RISK FACTOR FOR TUBERCULOSIS IN IMMIGRANT SOUTH LONDON ASIANS

Background - In a previous retrospective study of tuberculosis in sout h London among Asian immigrants from the Indian subcontinent Hindu Asi ans were found to have a significantly increased risk for tuberculosis compared with Muslims. This finding has been further investigated by examining the role of socioeconomic and lifestyle variables, including diet, as risk factors for tuberculosis in Asian immigrants from the I ndian subcontinent resident in south London. Methods - Using a case-co ntrol study technique Asian immigrants from the Indian subcontinent di agnosed with tuberculosis during the past 10 years and two Asian contr ol groups (community and outpatient clinic controls) from the Indian s ubcontinent were investigated. Cases and community controls were appro ached by letter. A structured questionnaire concerning a range of demo graphic, migration, socioeconomic, dietary, and health topics was admi nistered by a single trained interviewer to subjects (56 cases and 100 controls) who agreed to participate. Results - The results confirmed earlier findings that Hindu Asians had an increased risk of tuberculos is compared with Muslims. However, further analysis revealed that reli gion had no independent influence after adjustment for vegetarianism ( common among Hindu Asians). Unadjusted odds ratios for tuberculosis am ong vegetarians were 2.7 (95% CI 1.1 to 6.4) using community controls, and 4.3 (95% CI 1.8 to 10.4) using clinic controls. There was a trend of increasing risk of tuberculosis with decreasing frequency of meat or fish consumption. Lactovegetarians had an 8.5 fold risk (95% CI 1.6 to 45.4) compared with daily meat/ fish eaters. Adjustment for a rang e of other socioeconomic, migration, and lifestyle variables made litt le difference to the relative risks derived using either community or clinic controls. Conclusions - These results indicate that a vegetaria n diet is an independent risk factor for tuberculosis in immigrant Asi ans. The mechanism is unexplained. However, vitamin D deficiency, comm on among vegetarian Asians in south London, is known to affect immunol ogical competence. Decreased immunocompetence associated with a vegeta rian diet might result in increased mycobacterial reactivation among A sians from the Indian subcontinent.