BRONCHIAL REACTIVITY AND DIETARY ANTIOXIDANTS

Background - It has been postulated that dietary antioxidants may infl uence the expression of allergic diseases and asthma. To test this hyp othesis a case-control study was performed, nested in a cross sectiona l study of a random sample of adults, to investigate the relationship between allergic disease and dietary antioxidants. Methods - The study was performed in rural general practices in Grampian, Scotland. A val idated dietary questionnaire was used to measure food intake of cases, defined, firstly, as people with seasonal allergic-type symptoms and, secondly, those with bronchial hyperreactivity confirmed by methachol ine challenge, and of controls without allergic symptoms or bronchial reactivity. Results - Cases with seasonal symptoms did not differ from controls except with respect to the presence of atopy and an increase d risk of symptoms associated with the lowest intake of zinc. The lowe st intakes of vitamin C and manganese were associated with more than f ivefold increased risks of bronchial reactivity. Decreasing intakes of magnesium were also significantly associated with an increased risk o f hyperreactivity. Conclusions - This study provides evidence that die t may have a modulatory effect on bronchial reactivity, and is consist ent with the hypothesis that the observed reduction in antioxidant int ake in the British diet over the last 25 years has been a factor in th e increase in the prevalence of asthma over this period.