Energy balance in children with cystic fibrosis

Nutrition Research Newsletter, Oct, 2006

Cystic fibrosis (CF) is a recessive disease in which defective functioning of the cystic fibrosis transmembrane conductance regulator chloride channel results in dehydrated secretions that block the ducts of organs such as the pancreas and lungs, which leads to a deterioration of the functions. The predicted survival age for persons with CF in 2003 was 33 years. Survival is affected by interrelated factors, such as lung disease severity and growth, which in turn are affected by nutritional status. Despite interventions such as the use of enzyme therapy, enteral supplements, and nutritional counseling to maximize nutritional status, undernutrition and suboptimal growth continue to be common findings in children with CF. To plan effective malnutrition prevention and treatment interventions for children with CF, an understanding of energy balance is required. Energy balance includes energy intake (EI), energy expenditure (EE), energy loss in stool due to maldigestion and malabsorption, and energy storage or tissue accretion in children.

No studies have measured all aspects of the energy balance equation (EE, EI, fecal energy loss, and energy storage), both simultaneously and longitudinally, in children with CE Furthermore, few studies to date have explored the effect of a chronic disease on the reporting accuracy of dietary intake in children, especially one in which nutritional status and growth are negatively affected. Therefore, Trabulsi et al. set out to describe energy balance and reporting accuracy in children with CF and pancreatic insufficiency (PI) by evaluating the relations between EI, EE, fecal energy loss, nutritional stares, and growth, with the belief that improved knowledge of energy balance and reporting accuracy will lead to more effective strategies to prevent and treat malnutrition.

The subjects were 69 participants of a 24-month prospective study of children 6 years to 10 years of age with CF and PI. EE, EI, fecal energy loss, and anthropometric measures were obtained at baseline and at 24 months. A seven day food record was completed at baseline and at the end of the study. At the baseline and 24-month visits, TEE was measured with the doubly labeled water (DLW) technique. The ratio of reported EI from the diet record minus fecal fat energy loss (FL), to measured EE by DLW was used to categorize subjects as accurate reporters, underreporters, or overreporters of EI.

The children had suboptimal growth at baseline in their weight-for-age z score, adjusted height-for-age z score, and BMI z score, and these variables remained suboptimal at 24 months. The median ratios of EI to EE at baseline and 24 months were 1.15 and 1.18, respectively, which decreased to 1.09 and 1.10, respectively, when adjusted for fecal energy loss. At baseline, 7% of the subjects were underreporters of EI, 64% were accurate reporters, and 23% were overreporters; 24 mo later, 3% of the subjects were underreporters of EI, 59% were accurate reporters, and 28% were overreporters.

This study of energy balance and reporting accuracy in preadolescents with CF and PI found that suboptimal growth and nutritional status were present at the onset and conclusion of the 24-month study. The results suggest a weakness of the diet record at the individual level in young children with a nutrition-related disease and serve as a cautionary note to clinicians and researchers. Evaluation of energy balance with an objective measure, such as weight-gain velocity, is likely more reliable and useful in clinical care than is the use of a diet record. Future studies are needed to determine whether children with CF overreport intake when using retrospective diet assessment methods such as the 24 h dietary recall. Finally, studies are needed to confirm the observation of misreporting of EI in children with CF and in persons with other disease conditions in which nutritional status and growth are affected and emphasized as a component of routine care.

Jillian Trabulsi, Joan I. Schall, Richard F. Ittenbach, et al. Energy Balance and the Accuracy of Reported Energy Intake in Preadolescent Children with Cystic Fibrosis, Am J Clin Nutr; 84:523-530 (September 2006) [Address reprint requests to J Trabulsi, Divisions of Gastroenterology and Nutrition, The Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104. E-mail: trabulsi@email.chop.edu]