Abstract
There are plausible mechanisms for how dietary docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid, could prevent Crohn's disease (CD). To conduct a prospective study to investigate the association between increased intake of DHA and risk of CD. Overall, 229702 participants were recruited from nine European centres between 1991 and 1998. At recruitment, dietary intakes of DHA and fatty acids were measured using validated food frequency questionnaires. The cohort was monitored through to June 2004 to identify participants who developed incident CD. In a nested case-control analysis, each case was matched with four controls; odds ratios (ORs) were calculated for quintiles of DHA intake, adjusted for total energy intake, smoking, other dietary fatty acids, dietary vitamin D and body mass index. Seventy-three participants developed incident CD. All higher quintiles of DHA intake were inversely associated with development of CD; the highest quintile had the greatest effect size (OR=0.07; 95% CI=0.02-0.81). The OR trend across quintiles of DHA was 0.54 (95% CI=0.30-0.99, Ptrend =0.04). Including BMI in the multivariate analysis, due to its correlation with dietary fat showed similar associations. There were no associations with the other dietary fatty acids studied. There were inverse associations, with a biological gradient between increasing dietary docosahexaenoic acid intakes and incident Crohn's disease. Further studies in other populations should measure docosahexaenoic acid to determine if the association is consistent and the hypothesis tested in randomised controlled trials of purely docosahexaenoic acid supplementation.
Highlights
Crohn’s disease (CD) is a chronic inflammatory bowel disease (IBD) of unknown aetiology that can affect any part of the gastrointestinal tract
All higher quintiles of docosahexaenoic acid (DHA) intake were inversely associated with development of CD; the highest quintile had the greatest effect size (OR = 0.07; 95% confidence intervals (CI) = 0.02–0.81)
Cigarette smoking was positively associated with CD (OR = 2.40, 95% CI = 1.16–4.94; P = 0.02)
Summary
Crohn’s disease (CD) is a chronic inflammatory bowel disease (IBD) of unknown aetiology that can affect any part of the gastrointestinal tract. While genomic wide association studies have identified over 140 genetic risk loci for CD,[1] the risk contribution from these is estimated to be less than 25%.2. This implies that other exposures such as environmental/lifestyle variables, including diet maybe involved in CD aetiology.[3]. Emerging evidence reports that DHA and EPA can be metabolised to lipid mediators with anti-inflammatory and inflammation resolving properties.[8]
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