PT - JOURNAL ARTICLE AU - B D Patel AU - A A Welch AU - S A Bingham AU - R N Luben AU - N E Day AU - K-T Khaw AU - D A Lomas AU - N J Wareham TI - Dietary antioxidants and asthma in adults AID - 10.1136/thx.2004.024935 DP - 2006 May 01 TA - Thorax PG - 388--393 VI - 61 IP - 5 4099 - http://thorax.bmj.com/content/61/5/388.short 4100 - http://thorax.bmj.com/content/61/5/388.full SO - Thorax2006 May 01; 61 AB - Background: Several antioxidant nutrients have been reported to be inversely associated with asthma. A study was undertaken to assess the independent associations of these nutrients with asthma in adults. Methods: A nested case-control study was performed in 515 adults with physician diagnosed asthma and 515 matched controls using dietary data obtained from 7 day food diaries. The main outcome measures were physician diagnosed asthma and current symptomatic asthma (diagnosed asthma and self-reported wheeze within the previous 12 months). Results: Cases were similar to controls in age, sex, social class, and daily energy intake but had a lower median intake of fruit (132.1 v 149.1 g/day, p⩽0.05). 51.5% of the population reported zero consumption of citrus fruit; relative to these individuals, people who consumed >46.3 g/day had a reduced risk of diagnosed and symptomatic asthma (OR adjusted for potential confounders 0.59 (95% CI 0.43 to 0.82) and 0.51 (95% CI 0.33 to 0.79), respectively). In nutrient analysis, dietary vitamin C and manganese were inversely and independently associated with symptomatic asthma (adjusted OR per quintile increase 0.88 (95% CI 0.77 to 1.00) for vitamin C and 0.85 (95% CI 0.74 to 0.98) for manganese), but only manganese was independently associated with diagnosed asthma (OR 0.86 (95% CI 0.77 to 0.95)). Adjusted plasma levels of vitamin C were significantly lower in symptomatic cases than in controls (54.3 v 58.2 μmol/l, p = 0.003). Conclusions: Symptomatic asthma in adults is associated with a low dietary intake of fruit, the antioxidant nutrients vitamin C and manganese, and low plasma vitamin C levels. These findings suggest that diet may be a potentially modifiable risk factor for the development of asthma.