Oregon Health & Science University
Background: A recent study showed significantly higher body fat percentage among subjects with phenylketonuria (PKU) compared to controls. Several studies have suggested a relationship between body composition and blood phenylalanine (phe) concentrations, but this has not been consistently reported in the literature. The body composition of patients with PKU followed at Doernbecher Children’s Hospital is unknown. Objective: We aimed to determine if there is a difference in body composition of patients with PKU and patients in the general pediatric population. Furthermore, within the population with PKU we aimed to determine if there is a relationship between body composition and blood phe control. Methods: The study was conducted at the OHSU Metabolic Clinic and the PKU Family Camp. Dietary intake, height, weight, Lean Body Mass (LBM), and Fat Mass (FM) were measured in 30 subjects without PKU aged 5 to 18 years (Males n=18, Females n=12) and in 30 age and gender matched control subjects. Historical dried blood spot phe and tyrosine concentrations, were collected from the medical record of subjects with PKU. Body Mass Index (BMI) was calculated and all parameters were charted on sex-specific CDC growth charts and expressed as a percentile. Results: Subjects with PKU had significantly lower height z-scores (-0.515 ± 1.027 vs. 0.420 ± 1.044; p=0.0034) than controls, specifically in males (- 0.741 ± 1.002 vs. 0.546 ± 1.108; p= 0.0023) and not in females (p=0.4073). There was a trend for subjects with PKU to have significantly higher fat mass percentage (FM%) (17.62 ± 7.671% vs. 14.79 ± 7.84%; p=0.0593) compared to control subjects due to higher FM% in male subjects with PKU (14.61 ± 4.903% vs. 10.19 ± 5.943; p= 0.0262) but not in females (22.13 ± 49.003% vs. 20.61 ± 6.77%; p=0.340). Sixty percent of the subjects with PKU and 80% of the controls were normal weight (BMI< 85th percentile n=18 vs. n=24), 30% of the subjects with PKU and 6.67% of the controls were overweight (BMI 85th-95th percentile n=9 vs. n=2), and 10% of the subjects with PKU and 13.33% of the controls were obese (BMI > 95th percentile n=3 vs. n=4). Percent of total energy from protein and lipids was significantly lower, while percent energy from carbohydrate was significantly higher in subjects with PKU when compared to controls. A multiple linear regression analysis was used to determine if FM% was significantly associated with dried blood spot phe independent of age. Age was a significant factor contributing to dried blood spot phe (p=0.0033); FM% was also significantly associated with dried blood spot phe (p=0.0300). Conclusions: Subjects with PKU may have altered body composition with increased FM% and decreased LBM% associated with a high carbohydrate, low protein and lipid containing diet. FM% appears to be positively related to dried blood spot phe so that as FM% increases, phe increases. Future studies may explore if improved metabolic control with lower blood phe concentrations would be associated with a lower FM and higher LBM.
Graduate Programs in Human Nutrition
School of Medicine
Hammons, Melissa M., "Nutrient intake and body composition in children with phenylketonuria" (2015). Scholar Archive. 3644.