Nutritional Advices for Patients with Cystic Fibrosis

Nutritional Advices for Patients with Cystic Fibrosis


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Nutritional Advices for Patients with Cystic Fibrosis

Cystic fibrosis (CF) is a debilitating, life threatening, autosomal recessive and hereditary disease. In addition, the chronic disease has no cure yet. The disease afflicts approximately 70,000 people worldwide 30,000 of whom are in the United States. Its prevalence is highest among Caucasians, although it also affects people from other ethnic groups. According to Sharma (2020), and the University of Wisconsin Hospital and Clinics Authority (2020), the disease prevalence is 1:3,200-3,500 births among children of Caucasian descent, 1:9,200-9,5000 births among Hispanics, 1:15,000-17,000 among those of Black descent, and 1:31,000 births among children of Asian origin. Altogether, in the United States, the prevalence is about one in every 4,000 people of diverse ethnicities, and is particularly high in small isolated communities such as the Amish in Ohio due to their low genetic variety and high chances of passing the mutated gene to children by their parents (Scotet, L’Hostis, & Férec, 2020). The diagnosis rate is high in the United States because screening of infants is mandatory in the United States.  About 1000 new cases are diagnosed every year in the country, 75% of which are in children aged below 2 years (Luo, 2018). About 25% of children born of two parents that are carriers of the defective gene will have cystic fibrosis while another 50 % are likely to be carriers but will not develop the disease; therefore, about 10 million people in the United States are unaware that they carry the defective gene (Luo, 2018). Nonetheless, the disease is usually screened using the sweat test

Cystic fibrosis manifests in patients as the formation and accumulation of viscous mucous, which lines the respiratory and gastrointestinal system, with the lungs and the pancreases exhibiting most dysfunction. Its occurrence has been attributed to a defective gene (Cystic fibrosistransmembrane conductance regulator gene), which causes the formation of unusually thick and sticky mucous and has over 1,700 mutations that are known currently (Luo, 2018). Its symptoms include persistent coughs, wheezing and shortness of breath, salty-tasking skin, bulky and greasy stool, nasal polyps, and poor weight gain, especially in children and adolescents (Luo, 2018). Its debilitating effects can lead to accompanying illnesses, such as pneumonia, bronchitis, osteoporosis, and infertility in men. 

Considering that the disease is still incurable, the lives of those with cystic fibrosis have been elongated through nutritional management, clinical interventions, and psychosocial support. The estimated median survival age in the United States is currently at 47.4 years and can extend to the age of 60 those that are already past their 40th birthday, which has more than doubled in the last 35 years (Scotet, L’Hostis, & Férec, 2020).  Advancements in nutritional management of cystic fibrosis have helped improve the quality of life of patients. This study focuses on the nutritional advices for patients with cystic fibrosis. This will required the understanding of the cystic fibrosis pathophysiology, metabolism of patients with cystic fibrosis, and nutritional therapy, before exploring diet recommendations.

Definition of Concepts

The concepts associated with cystic fibrosis pathophysiology, metabolism of patients with cystic fibrosis, and nutritional therapy, and diet recommendations are explored and explained.

Cystic Fibrosis Pathophysiology

Pathophysiology is the functional changes of dysfunctions that are associated with a disease, thus manifesting an abnormal state. In this regard, cystic fibrosis alters the normal state or bodily functions of the body of the patient. More specifically, cystic fibrosis is associated with the defective or mutated cystic fibrosistransmembrane conductance regulator (CFTR) gene responsible for encoding the CFTR protein (Anderson, Miles, & Tierney, 2017). This protein acts as a chloride channel, which is regulated by the concentration gradient through the action of adenosine triphosphate (ATP) and cyclic adenosine monophosphate (cAMP). The CFTR protein is found in the submucosal glands and epithelial cells found in several bodily systems, such as the respiratory tract, the gastrointestinal tract, the reproductive tract and the pancreas. The cystic fibrosistransmembrane conductance regulator gene mutations present six classes of defects, namely i) accelerated ion channel turnover from the surface of epithelial cells, ii) defective chloride channel gating and conductance, iii) defective CFTR protein maturation, iv) diminished transcription due to splicing and promoter abnormalities, v) suppressed ATP binding and hydrolysis, and complete absence of CFTR protein synthesis (Brown, White, & Tobin, 2017; Sharma, 2020).

In the respiratory tract, the defective gene causes a reduction of airway surface liquid (ASL), which is critical as a mucociliary escalator and instrumental in several immunological functions. Consequently, the chloride ion (Cl) movement and epithelial sodium channels (ENaC) which allow the movement of sodium (Na+) ions are disrupted, reducing the water levels in epithelial secretions. Altogether, the mutant CFTR produces defective CFTR protein which increases the reabsorption of water and sodium ions and decreases the secretion of chloride ions across epithelial cells in different body systems. The lung lumens become clogged with thick mucus and become fertile for bacterial growth, which compromises the bodily immune system and makes the respiratory tract prone to infections and inflammations. Moreover, mucous clearance is impeded, causing respiratory difficulties. 

In the gastrointestinal tract, the defective gene causes the secretion of viscous mucous s well, resulting in bowel obstruction that is evidenced as constipation. Such intestinal obstruction causes jaundice in infants, meconium ileus in children, and cystic fibrosis –related liver disease and distal intestinal obstruction syndrome (DIOS) in adults. Similarly, like in the respiratory tract, the presence of the thick mucus layer promotes the proliferation of pathogens and the reduction of probiotics (Anderson, Miles, & Tierney, 2017). This leads to the development of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) considering the immunological responses at this site are compromised (Anderson, Miles, & Tierney, 2017).

In the reproductive tract, men develop the congenital absence of the vas deferens (CAVD), in which the two vas deferens are not developed properly at the fetal stage. Consequently, 98% of males with cystic fibrosis are infertile because their sperms cannot be transported to the penis. 

In the pancreas, pancreatic insufficiency develops due to the occlusion of the pancreatic duct.  Consequently, a patient develops cystic fibrosis-related diabetes mellitus because the endocrine processes in the pancreas, such as the secretion of insulin, are disrupted due to the damaged organ.   

Metabolism of Patients with Cystic Fibrosis

Metabolism is a set of the chemical reactions that maintain the living and functional state of cells and the entire organism. Cystic fibrosis patients metabolize proteins, carbohydrates, and mineral abnormally, usually because they do not produce sufficient or no pancreatic enzymes to aid the metabolic processes. In turn, the protein, carbohydrate and mineral metabolisms are depressed and the body responds through protein catabolism, which breaks down the muscular proteins into amino acids and produces energy to meet the deficiencies in the body. This process is mediated by circulating cytokines, whose levels are high in cystic fibrosis patients. Carbohydrate metabolism is abnormal because the body is unable to produce energy from glucose, thus causing energy deficiency in CF patients. Beta cell function is lost and abnormal sugar levels result leading to hyperglycemia (Jones & Sainsbury, 2016). Minerals play a critical role in the immunological processes, respiratory, and bone density accumulation process, and their malabsorption may cause an increased risk of infections and inflammations, poor oxygen and nutrient transport in the blood, and weakened bones (Lee, et al., 2015). For instance, vitamin D is metabolized to 25-hydroxyvitamin D or calcifediol and later to calcitriol which are pre-hormonal compounds that circulates in the blood stream and is responsible for regulating calcium an phosphate in the blood. Low levels of calcifediol and calcitriol due to CF contribute to the elevated risk of osteoporosis due to insufficient bone calcification.

Nutritional Therapy

Nutrition therapy is a treatment intervention that focuses on changes in diet usually through the adjustment of the methods, quality, and quantity of nutrient ingestion. It is critical for the maintenance of good nutritional status of individuals with cystic fibrosis and has been associated with elongated survivability and improved quality of life of these patients (López-Mejía et al., 2018). Nutritional management used to implement the nutritional therapy is a multidisciplinary undertaking that involves a physician, and respiratory therapist, a nurse, a dietitian and a social worker, who design a personalized nutrition regimen for each individual patient (Collins, 2018). Nutritional therapy focuses on the delivery of high calories to the body to counter the low nutrient absorption. However, therapy should be preceded by a comprehensive nutritional assessment to determine the needs of the patient.  The nutritional status assessment includes the determination of body composition, micronutrient levels, glucose tolerance, and bone density. 

Patients with cystic fibrosis often suffer from malnutrition and poor growth because of insufficient caloric intake, increased energy metabolism and energy loses caused by the malabsorption of vital nutrients (López-Mejía et al., 2018). In turn, the patients need higher levels of lipids, proteins and energy-rich diets than healthy individuals, and nutrition therapy focuses on increasing the absorption of these nutrients.  In this regard, the nutritional therapy recommended for these patients comprises the intake of fat-soluble vitamin supplements (vitamin A, D, E and K), intake of micronutrient supplements rich in sodium, iron and calcium, and individualized pancreatic enzyme replacement therapy (PERT) to counter the exocrine pancreatic insufficiency on a majority (80%-90%) of patients (Calvo-Lerma et al., 2017; López-Mejía et al., 2018). However, innovative nutritional therapies involving probiotics supplementation, omega-3 fatty acids and antioxidants are still under developing and promise to expand the therapeutic regime available to patients (López-Mejía et al., 2018).

Alternative nutritional therapies employ CFTR modulators to improve the nutritional status of patients. These modulators are categorized as potentiators and correctors. Potentiators such as Ivacaftor improve the respiratory function and reduce the worsening of pulmonary condition alongside improving pancreatic function and enhancing the control of diabetes, resulting in increased body weight (Hollander, de Roos, & Heijerman, 2017). However, nutritional guidelines result from the consensus of experts rather that evidence-based data due to the absence of coefficient and conclusive randomized control trials (Collins, 2018).

Diet Recommendations

Although it is recommended for patients with cystic fibrosis to eat a balanced diet, diets with excess or additional protein, salt, iron, calcium and zinc are endorsed. In this regard, patients are advised to eat more beans, nuts, eggs, meat, and fish as sources of protein. People with cystic fibrosis, and especially adolescents, tend to lose much salt during physical exercise and in hot weather. Therefore, they are advised to add salt to their meals of consume salty snack often to maintain their bodily sodium and chloride ion balances. Patients are likely to experience respiratory difficulties and immunological challenges. However, iron plays a critical role in oxygen transportation and fighting infections. Therefore, patients are advised to eat foods rich in iron, such as green leafy vegetables, dried fruits, meats, and fortified cereals.  In addition, patients are at risk of developing osteoporosis due to calcium deficiency. Therefore, they are advised to consume more full-fat dairy products and fruit juices, which are calcium-rich. Zinc is critical in immunological processes, healing and growth in CF patients. Therefore, these individuals are advices to consume high amounts of seafood, eggs, liver, and meats.

Conclusions and Recommendations

Nutritional advices to patients with cystic fibrosis are based on the comprehensive understanding of the pathophysiology of the condition, metabolism in patients, nutritional therapy and dietary requirements. Patient screening is critical in understanding the nutritional need and designing the nutritional therapy, which is performed by a multidisciplinary team. Therefore, it is recommended that patient undergo nutritional assessment early to benefit from the nutrition therapy and improve the length and quality of life. It is also recommended that the nutritional therapy be individualized, based on the particular needs of each patient. Moreover, it is recommended that patients adhere to the nutritional therapy strictly to reap its full benefits.  


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