Smoking and diet can affect the evolution of inflammatory bowel disease

The factors that determine the development of inflammatory bowel disease are not entirely known. However, previous infections, genetics and environmental factors, such as smoking or diet, can influence its development and progression.

Inflammatory bowel disease is characterised by the presence of chronic inflammatory lesions in the digestive tract. It consists of ulcerative colitis and Crohn's disease. These diseases affect around 300,000 people in Spain, and every year 10,000 new cases are diagnosed The factors that influence the development of this disease are not fully known, but certain aspects, such as previous infections, genetics and environmental issues may have an influence. Despite the fact that infections and genetics are difficult to control, some habits can improve the evolution of this disease; for example, not smoking when having Crohn's disease. There are no specific recommendations regarding diet, except that it should be balanced and healthy.

Certain gastrointestinal infections have been linked to both ulcerative colitis and Crohn's disease. Although inflammatory bowel disease is not infectious, numerous studies show that having an earlier intestinal infection can increase the risk of developing inflammatory bowel disease. Thus, infections by certain bacterial species (Salmonella, Campylobacter or Clostridioles difficile) or norovirus (a highly contagious type of virus) are associated with increased risk. Meanwhile, infection with Helicobacter pylori or helminths (a type of parasite) may be a protective factor for the development of these diseases.

In addition, 5-20% of people with ulcerative colitis or Crohn's disease have a first-degree relative who also has the disease. This indicates that hereditary factors (linked to DNA or genetics) may contribute to the development of the disease. In fact, around 160 genetic mutations have been identified in patients with inflammatory bowel disease that affect the risk of developing the disease. However, there are studies in identical twins where only one of them has the disease, which shows that genetics is not the only triggering factor, although it can increase the risk.

Thus, environmental and gene-independent aspects are also considered to play a role. For example, being a smoker increases the risk of developing Crohn's disease. Patients with the disease who continue to smoke are associated with a worse prognosis in terms of the risk of needing immunosuppressive treatment and/or surgery.

Other environmental factors such as stress, exposure to pollutants and even diet are difficult to study. Measuring their effects requires monitoring patients for long periods of time. Nevertheless, recent studies modifying the diet of patients are beginning to shed light on the role that food can play in the development and maintenance of the disease.

Information documented by:

Dr Azucena Salas, head of the IDIBAPS Inflammatory Bowel Disease research group and CIBER-EHD and Dr Ingrid Ordás, gastroenterologist at the Inflammatory Bowel Disease Unit of the Clínic-IDIBAPS and member of CIBER-EHD.