Dietary total antioxidant capacity and current asthma in Spanish schoolchildren: a case control–control study

The aim of this work was to study the relationship between dietary total antioxidant capacity (TAC) and current asthma in a group of Spanish schoolchildren. A total of 78 Spanish schoolchildren (26 asthmatic and 52 healthy controls) were randomly selected from a cohort of 564 children (9–12 years of age). The weight and height of all subjects were recorded. A questionnaire, completed by the subjects' parents, was used to obtain personal and health information. Current asthma was established when children had ever had asthma, they had been diagnosed with asthma by a physician, and they had been treated with medications at some time in the previous 12 months. Food intake was monitored using a 3-day food record. All consumed foods were converted into energy and nutrients. Dietary TAC was evaluated using the ferric reducing antioxidant power (FRAP), radical-trapping antioxidant parameter (TRAP), and Trolox equivalent antioxidant capacity (TEAC) assays. The TAC measured using all the assays was significantly lower in children with asthma than in children without this condition (2.95 (2.10–3.75) mmol Fe(II)/day vs. 3.70 (3.08–4.49) mmol Fe(II)/day, p < 0.01; 1.50 (1.06–2.05) mmol Trolox equivalents/day vs. 2.10 (1.40–2.65) mmol Trolox equivalents/day, p < 0.05; and 1.60 (1.08–2.00) mmol Trolox equivalents/day vs. 1.85 (1.50–2.68) mmol Trolox equivalents/day, p < 0.05 for FRAP, TEAC, and TRAP, respectively). After adjusting for energy intake, children with FRAP values higher than 3.5 mmol Fe(II)/day (p50) and TEAC values higher than 1.9 mmol Trolox equivalents/day (p50) had 22.6 and 35.0 %, respectively, lower likelihood of suffering asthma episodes than children with lower values. When logistic regression analysis was performed separately for children with nonsmoker and smoker (at least one) parents, the association between dietary TAC and asthma was only observed in the nonsmoker group (OR = 0.257, 95 % CI = 0.107–0.618, p = 0.002 for FRAP; OR = 0.212, 95 % CI = 0.069–0.639, p = 0.006 for TEAC; and OR = 0.264, 95 % CI = 0.091–0.769, p = 0.015 for TRAP assay). Conclusion: Dietary TAC may have a favorable role in asthma in children and, specially, in those with nonsmoker parents.