Inflammation anywhere along the digestive tract disrupts this normal process. Inflammatory bowel disease (IBD) can be very painful and disruptive, and in some cases, it may even be life-threatening.
The exact cause of IBD is unknown. However, genetics and problems with the immune system have been associated with IBD. Countries in Africa, Asia, the Middle East and South America have seen a rise in incidence of IBD as they have become increasingly industrialised and westernised, a new study has found.
The research, a collaboration between the University of Birmingham, the University of Calgary, Canada, and the Chinese University of Hong Kong, is the most definitive and comprehensive study of the global epidemiology of inflammatory bowel disease.
The study, published in The Lancet, was a systematic review of 147 world-wide observational studies reporting on the incidence or prevalence of two of the main conditions of inflammatory bowel disease - Crohn's disease and ulcerative colitis - between 1990 and 2016.
Professor Subrata Ghosh, Director of the Institute of Translational Medicine, said: "Our study shows that, at the turn of the 21st century, inflammatory bowel disease has become a global disease with accelerating incidence in newly industrialised countries whose societies have become more westernised.
"We have shown an accelerating incidence in countries in Africa, Asia, the Middle East and South America that mirrors inflammatory bowel disease incidence in the Western world during the latter half of the 20th century."
Dr Gilaad Kaplan, of the University of Calgary in Canada, said: "While our study demonstrates a paradigm shift whereby the incidence of inflammatory bowel disease in most Western countries has begun to stabilize and in some regions decrease, it is important to note that the prevalence of the disease is now 0.3% of the population in North America, Australia and most countries in Europe.
"The high prevalence of this disease in the Western world will challenge clinicians and health policy makers to provide quality and cost-efficient care to patients with this condition."
Professor Siew Ng, of The Chinese University of Hong Kong, adds: "The rapid increase in incidence in many countries, especially in children, within one to two decades suggests strong environmental influence within a genetically susceptible population.
"The peak in the incidence of this disease has likely not transpired in newly industrialized countries. Consequently, these countries will need to prepare their clinical infrastructure and personnel to manage what is a complex and costly disease to treat."