Evidence-Based Medicine
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jul 21, 2016; 22(27): 6296-6317
Published online Jul 21, 2016. doi: 10.3748/wjg.v22.i27.6296
Environmental risk factors for inflammatory bowel diseases: Evidence based literature review
Ayokunle T Abegunde, Bashir H Muhammad, Owais Bhatti, Tauseef Ali
Ayokunle T Abegunde, Tauseef Ali, Section of Digestive Diseases and Nutrition, Department of Medicine, Oklahoma University Health Sciences Center, Oklahoma City, OK 73104, United States
Bashir H Muhammad, Owais Bhatti, Department of Medicine, Oklahoma University Health Sciences Center, Oklahoma City, OK 73104, United States
Author contributions: Abegunde AT, Muhammad BH, Bhatti O and Ali T contributed equally to the work; Abegunde AT, Bhatti O and Ali T conceptualized and designed the review; Abegunde AT, Muhammad BH, Bhatti O and Ali T contributed to search of literature and data extraction; Abegunde AT, Muhammad BH, Bhatti O and Ali T drafted the manuscript; all authors reviewed and approved the final manuscript as submitted.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Tauseef Ali, MD, Section of Digestive Diseases and Nutrition, Department of Medicine, Oklahoma University Health Sciences Center, 920 Stanton L Young Boulevard, Oklahoma City, OK 73104, United States. drtauseef@yahoo.com
Telephone: +1-405-2715428
Received: March 11, 2016
Peer-review started: March 11, 2016
First decision: April 14, 2016
Revised: May 19, 2016
Accepted: June 28, 2016
Article in press: June 29, 2016
Published online: July 21, 2016
Processing time: 126 Days and 4.9 Hours
Abstract

AIM: Advances in genetics and immunology have contributed to the current understanding of the pathogenesis of inflammatory bowel diseases (IBD).

METHODS: The current opinion on the pathogenesis of IBD suggests that genetically susceptible individuals develop intolerance to dysregulated gut microflora (dysbiosis) and chronic inflammation develops as a result of environmental insults. Environmental exposures are innumerable with varying effects during the life course of individuals with IBD. Studying the relationship between environmental factors and IBD may provide the missing link to increasing our understanding of the etiology and increased incidence of IBD in recent years with implications for prevention, diagnosis, and treatment. Environmental factors are heterogeneous and genetic predisposition, immune dysregulation, or dysbiosis do not lead to the development of IBD in isolation.

RESULTS: Current challenges in the study of environmental factors and IBD are how to effectively translate promising results from experimental studies to humans in order to develop models that incorporate the complex interactions between the environment, genetics, immunology, and gut microbiota, and limited high quality interventional studies assessing the effect of modifying environmental factors on the natural history and patient outcomes in IBD.

CONCLUSION: This article critically reviews the current evidence on environmental risk factors for IBD and proposes directions for future research.

Keywords: Environmental factors; Inflammatory bowel disease; Exposomes

Core tip: Environmental factors are heterogeneous with varying effects during the life course of individuals with inflammatory bowel diseases (IBD). Studying the relationship between environmental factors and IBD may provide the missing link to increasing our understanding of the etiology and increased incidence of IBD in recent years with implications for prevention, diagnosis, and treatment. However, the impact of modifying specific environmental factors on causation and established disease remain poorly studied with limited high quality data from interventional studies to guide clinical practice.