Role of environmental factors in the development of inflammatory bowel disease

Inflammatory Bowel Disease (IBD) is a chronic inflammatory disorder of the colon. The disease is more prevalent in developed countries and an increase in IBD cases is observed in developing countries. In susceptible individuals, IBD occur due to an imbalance between genetic and environmental factors. Alteration in the gut microbiota can influence the development of immune repertoire of an individual, thereby playing a vital role in the development of IBD. The two main disease entities of IBD are Crohn’s disease (CD) and Ulcerative colitis (UC). This review focuses on various environmental factors involved in development of IBD. Such environmental factors comprise of hygiene, air pollution, smoking, oral contraceptives (OCPs), Non-steroidal Anti-inflammatory Drugs (NSAIDs), stress and diet. Higher hygiene standards will lead to greater risk of development of IBD, due to lack of exposure to enteric pathogens. Air pollutants increase the risk of development of IBD. Smoking has a protective effect in UC and an opposite effect in CD. Prolong use of OCPs and NSAIDs has been associated with the risk of IBD. Intake of high protein diet increases the risk of IBD. On the other hand, fruits and vegetables have a protective effect in IBD. Stress and depression worsen the symptoms of IBD and increases the chance of relapse of IBD in patients. However, these environmental factors do not show a consistent result and further research is required for deciphering the role of these factors in the development of IBD.