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

Authors

  • Jinming GAO,

    Corresponding author
    1. Department of Respiratory Diseases, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China,
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  • Xiang GAO,

    1. Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, USA, and
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  • Weijuan LI,

    1. Department of Respiratory Diseases, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China,
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  • Yuanjue ZHU,

    1. Department of Respiratory Diseases, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China,
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  • Philip J. THOMPSON

    1. Lung Institute of Western Australia and Centre for Asthma, Allergy and Respiratory Research, The University of Western Australia, Perth, Western Australia, Australia
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Jinming Gao, Department of Respiratory Diseases, Peking Union Medical College Hospital, 1 Shuaifuyuan, Dongcheng District, Beijing 100730, China. Email: gaojm@pumch.cn

Abstract

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.

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