Cystic fibrosis is the most common fatal genetic disorder in North America. The disorder produces thick, sticky mucus secretions that may seriously impair the function of multiple organs in the body. Most notably, these organs are the pancreas and lungs. Just a few decades ago, an infant born with CF seldom survived to adulthood. Today, the outlook is much brighter, with adults reaching their 30’s, 40’s, and some even into their 50’s.
Cystic fibrosis has three major consequences: chronic lung disease, pancreatic insufficiency, and abnormally high electrolyte concentrations in the sweat. Chronic lung disease develops because the airways in the lungs become congested with mucus, causing breathings to be strenuous. As the thick mucus stagnates in the bronchial tubes, bacteria multiply there. Lung infections are the usual cause of death in people with cystic fibrosis.
Cystic fibrosis causes some degree of pancreatic insufficiency in all cases, with about 90% of cases serious enough to require enzyme replacement therapy. With aging, damage to the pancreas deteriorates. The thick mucus obstructs the pancreatic ducts and interferes with the secretion of digestive enzymes, pancreatic juices, and pancreatic hormones. Eventually, the pancreatic cells are surrounded by mucus and are gradually replaced by fibrous tissues. Malabsorption of many nutrients including fat, protein, vitamins, and minerals often leads to malnutrition. Additionally, the secretion of insulin may be affected resulting in glucose intolerance and diabetes.
The therapy of cystic fibrosis aims to promote appropriate growth and development and prevent respiratory failure and complications. Treatment includes respiratory, diet, and drug therapy.
Nutrient losses through malabsorption, frequent infections, rapid turnover rate of protein and essential fatty acids, high protein catabolism, and high basal energy expenditures raise energy needs for people with cystic fibrosis to between 120%-150% of the RDA for gender and age. Extra energy is needed simply to breathe. RDs estimate individual energy requirements based on basal metabolic rate, activity level, pulmonary function, and degree of malabsorption.
Obtaining enough energy can be complicated, but because people with CF frequently experience a loss of appetite that is aggravated by repeated infections, emotional stress, and drug therapy. Coughing to clear the lungs may trigger vomiting or reflux of foods from the stomach. Thus the person with cystic fibrosis finds it difficult to take in enough food energy, protein, and other nutrients to meet needs.