Purpose: Fish consumption and dietary intake of n-3 polyunsaturated acids (PUFAs) may be associated with inflammatory bowel disease (IBD). We aimed to conduct a systematic review and summarize published articles on the association between fish consumption and dietary intake of n-3 PUFAs with the risk of IBD.

Methods: PubMed, Scopus, and Web of Science databases were used to conduct a comprehensive search and identify eligible literature published prior to January 2019. Fixed-effects model or random-effects models (DerSimonian-Laird method) were applied to pool the effect sizes. Cochrane Q test was used to trace the potential source of heterogeneity across studies.

Results: 12 studies (5 prospective and 7 case-control) were included in the systematic review, which ten of them were eligible for inclusion in the meta-analysis. Studies were included a total sample size of 282610 participants which 2002 of them were cases of IBD [1061 Crohn's disease (CD) and 937 ulcerative colitis (UC)]. A negative association was found between fish consumption and the incidence of CD (pooled effect size: 0.54, 95%CI: 0.31-0.96, P = 0.03). There was no relationship between total dietary n-3 PUFAs intake and IBD (pooled effect size: 1.17, 95%CI: 0.80-1.72, P = 0.41). A significant inverse association was observed between dietary long-chain n-3 PUFAs and the risk of UC (pooled effect size: 0.75, 95%CI: 0.57-0.98, P = 0.03). Moreover, no association was found between α-Linolenic acid (ALA) and IBD (pooled effect size: 1.17, 95%CI: 0.63-2.17, P = 0.62).

Conclusions: Findings showed a negative association between fish consumption and the risk of CD. Moreover, there was a significant inverse association between dietary long-chain n-3 PUFAs and the risk of UC.