The Digestive System & Cystic Fibrosis
Cystic fibrosis causes problems with the digestive system
The cystic fibrosis transmembrane conductance regulator (CFTR) protein is found on the surface of cells in many organs and tissues throughout the body. This means that people with CF can experience a wide range of symptoms. These symptoms, and how severe they are, can vary a lot between people with cystic fibrosis (CF). This variation is the result of each individual person’s CFTR mutations (their genotype), genes, and their surroundings.
The digestive system
The process of digestion involves breaking down the food you eat to absorb the nutrients it contains. This process begins in your mouth, and continues as the food passes down into your stomach and small intestine. Here, the pancreas plays an important role in breaking down and absorbing nutrients.
One of the main jobs of the pancreas is to make enzymes. Enzymes are chemicals that help the body break down the nutritional parts of the food we eat, including protein, fat, and carbohydrates. Once made, enzymes travel through channels (pancreatic ducts) to the small intestine where they break down food.
In a person with CF, pancreatic ducts can become blocked with mucus. This makes it harder for enzymes to enter the small intestine where they are needed to do their job.
Pancreatic ducts can become blocked with mucus
Without these enzymes in the small intestine, the body may have trouble breaking down food and absorbing vital nutrients. This can lead to:
- Poor growth, delayed puberty and slow weight gain, even if a lot of food is eaten
- Frequent, greasy and bulky stools or difficult bowel movements
Over time, mucus blockages can start to damage the cells of the pancreas and reduce enzyme production. This is extremely common in people with CF.
Alongside medication such as enzyme tablets, many people with CF are advised to follow a CF-specific diet to help them get the nutrients they need and to manage any digestive symptoms.
Cystic fibrosis–related diabetes (CFRD)
Around 1/3 of adults with CF are reported to have cystic fibrosis–related diabetes (CFRD).
As people with CF get older, damage to their pancreas can mean it stops producing enough insulin, a hormone that helps the body manage glucose levels in the blood. When a person doesn’t have enough insulin, they may develop diabetes.
Some people with CFRD may find they need to drink and urinate more, feel very tired, lose weight, or have trouble gaining weight. They may also experience a decrease in their lung function. Other people with CFRD, however, may not experience any symptoms.
Other digestion-related symptoms
People with CF may experience a variety of digestive problems, which may result in:
- Weight fluctuation
Some people with CF may experience weight loss, or struggle to gain weight for various reasons. These might include reduced flow of pancreatic enzymes to the small intestine making it hard to release the nutrients from food, needing extra energy to fight off infections and, for those with CFRD, not being able to use the sugar from the foods they eat.
- Distal intestinal obstruction syndrome (DIOS)
Some people with CF may produce stool that is thicker than usual because they have difficulties digesting food. This can block the small intestines, causing pain and nausea. DIOS treatment varies based upon the severity of the symptoms and obstruction.
- Gastro-oesophageal reflux disease (GORD)
GORD is very common in people with CF. GORD occurs when stomach acid travels upwards into the oesophagus (the tube that connects the mouth to the stomach). This may cause a heartburn sensation, pain and/or swelling.
Cystic Fibrosis Australia. Cystic Fibrosis in Australia 2014: 17th Annual Report from the Australian Cystic Fibrosis Data Registry. August 2016.
O'Sullivan B, Freedman S. Cystic fibrosis. Lancet. 2009; 373(9678): 1891–1904.
Cystic Fibrosis Foundation. The digestive tract. Available at: www.cff.org/Living-with-CF/Treatments-and-Therapies/Nutrition/The-Digestive-Tract/.
Rowe SM, Miller S, Sorscher EJ. Mechanisms of Disease: Cystic Fibrosis. N Engl J Med. 2005; 352: 1992–2001.
John Hopkins CF Centre. Diabetes. Available at: www.hopkinscf.org/living-with-cf/managing-treatments/diabetes/.
Robinson N, DiMango E. Prevalence of gastroesophageal reflux in cystic fibrosis and implications for lung disease. Ann Am Thorac Soc. 2014; 11(6): 964–968.