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Oxidative stress may be involved in the aetiology of inflammatory bowel disease and whether dietary polyphenols, which possess antioxidants properties, prevent its development is unknown.A total of 401,326 men and women aged 20 to 80 years from 8 countries were recruited between 1991 and 1998 and at baseline completed validated food frequency questionnaires. Dietary polyphenol intake was measured using Phenol-Explorer, a database with information on the content of 502 polyphenols. Incident cases of Crohn's diseases (CD) and ulcerative colitis (UC) were identified during the follow-up period of up to December 2010. A nested case–control study using conditional logistic regression estimated the odds ratios (ORs), and 95% confidence intervals, for polyphenol intake (categories based on quartiles) and developing CD or UC.In total, 110 CD (73% women) and 244 UC (57% women) cases were identified and matched to 440 and 976 controls, respectively. Total polyphenol intake was not associated with CD (P trend = 0.17) or UC (P trend = 0.16). For flavones and CD, there were reduced odds for all quartiles, which were statistically significant for the third (OR3rd versus 1st quartile = 0.33; 95% confidence interval, 0.15–0.69) and there was an inverse trend across quartiles (P = 0.03). Similarly, for resveratrol, there was an inverse association with CD (OR4th versus 1st quartile = 0.40; 95% confidence interval, 0.20–0.82) with an inverse trend across quartiles (P = 0.02). No significant associations between subtypes of polyphenols and UC were found. Effect modification by smoking in CD was documented with borderline statistical significance.The data supports a potential role of flavones and resveratrol in the risk of developing CD; future aetiological studies should investigate these dietary components and further examine the potential for residual confounding.