BACKGROUND: Antioxidant intake may reduce the risk of allergic disease by protecting against oxidative tissue damage. Major sources of antioxidants in the Western world are fruits, vegetables (vitamin C,β-carotene, α-tocopherol), meat and milk (selenium, magnesium, zinc). Children may exclude or eat less of some fruits and vegetables due to cross-reactivity between pollen and these foods, complicating assessment of causal relationships.

OBJECTIVE: To investigate the association between dietary antioxidant intake and allergic disease, taking potential reverse causation into account.

METHODS: Data on 2442 8-year-old children from the Swedish birth cohort study BAMSE were analysed. Children with completed parental questionnaires on exposures and health, including a food-frequency questionnaire and who provided a blood sample were included. Associations between antioxidant intake during the past year and current allergic disease were analysed using logistic regression.

RESULTS: An inverse association was observed between intake ofβ-carotene and rhinitis (OR(adj) , highest vs. lowest quartile, 0.67, 95% CI 0.49-0.93). Magnesium intake was inversely related to asthma (OR(adj) , 0.65, 95% CI 0.42-1.00) and atopic sensitisation (OR(adj) , 0.78, 95% CI 0.61-1.00). Following exclusion of children who avoided certain fruits, vegetables or milk due to allergic symptoms (n = 285), the inverse association remained between magnesium intake and asthma (OR(adj) , 0.58, 95% CI 0.35-0.98), whereas all other associations became non-significant.

CONCLUSION AND CLINICAL RELEVANCE: Diet modifications due to allergy may affect the antioxidant intake and needs to be considered when investigating the relationship between diet and allergic disease. Magnesium intake seems to have a protective effect on childhood asthma.