Introduction: Dietary fatty acids may be involved in the etiology of ulcerative colitis (UC). Arachidonic acid (AA), an n-6 polyunsaturated fatty acid, is a precursor of the proinflammatory cytokines prostaglandin E2 and leukotriene B4, and its metabolism is competitively inhibited by oleic acid (OA). This study aimed to prospectively investigate whether AA is positively and OA is negatively associated with incident UC development, using data from 7-day food diaries.
Methods: A total of 25 639 men and women, aged between 40 and 79 years, from Norfolk, UK, were recruited into the prospective European Prospective Investigation into Cancer (EPIC)-Norfolk cohort between 1993 and 1997. At baseline, participants completed 7-day food diaries, checked by nutritionists using a database containing 11 000 foods and 55 000 portion sizes. The cohort was monitored until June 2004 to identify participants who developed UC. Each patient was matched for age and sex with four controls, and conditional logistic regression was used to calculate adjusted odds ratios for AA and OA intakes, and UC association.
Results: Of the participants, 26 (58% men) developed incident UC (53% left sided) after a median follow-up time of 3.8 years (0.5-8.3 years). The highest AA tertile was positively associated with an odds ratio of 6.09 [95% confidence interval (CI) 1.05-35.23], with a trend across tertiles [odds ratio (OR) 2.43, 95% CI 1.06-5.61, P=0.04]. The highest tertile of OA intake was inversely associated with a 0.03 OR for UC (95% CI 0.002-0.56) and an inverse trend (OR 0.30, 95% CI 0.10-0.90, P=0.03).
Conclusion: Dietary AA was positively and OA was inversely associated with UC development, with large effect sizes in a dose-dependent manner. This supports roles for measuring these nutrients in future etiological studies and modifying intake in future interventional studies in patients with established disease.