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, ß-carotene, a-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.
To investigate the association between dietary antioxidant intake and allergic disease, taking potential reverse causation into account.
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.
An inverse association was observed between intake of ß-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.
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.
BACKGROUND: Earlier studies have given conflicting results regarding the effect of exposure to tobacco smoke on atopic sensibilization. METHODS: A cross-sectional study of present and former smoking habits in relation to atopic disorders from data on 6909 young and middle-aged adults (16-49 years) and their 4472 children (3-15 years) from the Swedish Survey of Living Conditions in 1996-97. RESULTS: The prevalence of allergic asthma and allergic rhino-conjunctivitis decreased, in a dose-response manner (P = 0.03 and P = 0.004, respectively), with increasing exposure to tobacco smoke in the adult study population. This pattern was little changed when potential confounders (sex, age, education, domicile, country of birth) were entered into a multivariate analysis: the adjusted odds ratio (OR) for allergic rhino-conjunctivitis was 0.5 (0.4-0.7) for those who smoked at least 20 cigarettes a day and OR 0.7 (0.6-0.9) for those smoking 10-19 cigarettes, compared with those who reported that they never had smoked Former smokers had a tendency for a slightly lower risk: OR 0.9 (0.8-1.0). In a multivariate analysis, children of mothers who smoked at least 15 cigarettes a day tended to have lower odds for suffering from allergic rhino-conjunctivitis, allergic asthma, atopic eczema and food allergy, compared to children of mothers who had never smoked (ORs 0.6-0.7). Children of fathers who had smoked at least 15 cigarettes a day had a similar tendency (ORs 0.7-0.9). CONCLUSIONS: This study demonstrates an association between current exposure to tobacco smoke and a low risk for atopic disorders in smokers themselves and a similar tendency in their children. There is a need for further studies with a prospective design to certify the causal direction of this association. Smoking habits and atopic disorder in parents should not be considered independent variables in epidemiological studies of the connection between exposure to tobacco smoke and atopy in children.