Observational studies on the effect of dietary antioxidants on asthma: A meta-analysis

Jinming Gao, Xiang Gao, Weijuan Li, Yuanjue Zhu, Philip J. Thompson

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


Background and objective: It has been suggested that the rapid increase in asthma prevalence may in part be due to a decrease in the intake of dietary antioxidants, including vitamin C, vitamin E and β-carotene. Epidemiological studies investigating the association between dietary antioxidant intake and asthma have generated inconsistent results. A meta-analysis was undertaken to examine the association between dietary antioxidant intake and the risk of asthma. Methods: The MEDLINE database was searched for observational studies in English-language journals from 1966 to March 2007. Data were extracted using standardized forms. Pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated using a random effects model. Ten studies were eligible for inclusion. Seven studies, comprising 13 653 subjects, used asthma or wheeze as their outcome; three studies explored the effect of antioxidant intake on lung function. Results: A higher dietary intake of antioxidants was not associated with a lower risk of having asthma. The pooled OR for having asthma were 1.06 (95% CI: 0.79-1.43) for subjects with a higher dietary vitamin C intake compared with those with a lower intake; 0.88 (95% CI: 0.61-1.25) for vitamin E; and 1.12 (95% CI: 0.77-1.62) for β-carotene. There was no significant association between dietary antioxidant intake and lung function except for a positive association between vitamin C intake and an increase in FEV1 (29.1 mL, 95% CI: -0.4-58.6, P = 0.05). Conclusions: This meta-analysis does not support the hypothesis that dietary intake of the antioxidants vitamins C and E and β-carotene influences the risk of asthma.

Original languageEnglish (US)
Pages (from-to)528-536
Number of pages9
Issue number4
StatePublished - Jun 2008

All Science Journal Classification (ASJC) codes

  • Pulmonary and Respiratory Medicine


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