Nutritional Consequences of Adhering to a Low Phenylalanine Diet for Late-Treated Adults with PKU

Abstract

Background: The main treatment for phenylketonuria (PKU) is a low phenylalanine (Phe) diet, phenylalaninefree protein substitute and low-protein special foods. This study describes dietary composition and nutritional status in late-diagnosed adult patients adhering to a PKU diet.Methods: Nineteen patients, followed at Oslo University Hospital in Norway, participated; median age was 48 years (range 26-66). Subjects were mild to severely mentally retarded. Food intake, clinical data and blood analyses relevant for nutritional status were assessed.Results: Median energy intake was 2,091 kcal/day (range 1,537-3,277 kcal/day). Carbohydrates constituted 59% (range 53-70%) of the total energy, including 15% from added sugar; 26% was from fat. The total protein intake was 1.02 g/kg/day (range 0.32-1.36 g/kg/day), including 0.74 g/kg/day (range 0.13-1.07 g/kg/day) from protein substitutes. Median dietary Phe intake was 746 mg/day (range 370-1,370 mg/day). Median serum Phe was 542 mmol/L (range 146-1,310 mg/day). Fortified protein substitutes supplied the main source of micronutrients. Iron intake was 39.5 mg/day (range 24.6-57 mg/day), exceeding the upper safe intake level. Intake of folate and folic acid, calculated as dietary folate equivalents, was 1,370 mg/day (range 347-1744 mg/day), and resulted in high blood folate concentrations. Median intake of vitamin B 12 was 7.0 mg/day (range 0.9-15.1 mg/day).Conclusions: The diet supplied adequate protein and energy. Fortification of the protein substitutes resulted in excess intake of micronutrients. The protein substitutes may require adjustment to meet nutritional recommendations for adults with PKU.

High Dietary Folic Acid and High Plasma Folate in Children and Adults with Phenylketonuria

“…Our findings are in accordance with other studies reporting about twice as high folate levels in PKU children and young adults than in controls (Colome et al 2003;Huemer et al 2008). A recent report of 19 Norwegian latetreated adults found high intakes of folic acid and corresponding high blood folate concentrations (Wiig et al 2013). Only one PKU center in Greece reported of lower folate levels in PKU children with good compliance compared to PKU children with less adherence to diet and to controls (Schulpis et al 2002).…”

“…Another study of 19 Norwegian late-treated adults found that about 85 % of dietary folate equivalents (DFEs) originated from folic acid in the protein substitute. The remaining 15 % were from specially manufactured low protein foods, vegetables, fruits, and small amounts of dairy products (Wiig et al 2013).…”

“…There are several commercial protein substitutes available containing different amounts of folic acid. For patients adhering with the low protein diet, the intake of folate from natural sources is minor compared to the amount obtained from protein substitutes (Wiig et al 2013). The same is true for vitamin B12, as the diet allows very limited amounts of animal products (Wiig et al 2013).…”

Micronutrients, Essential Fatty Acids and Bone Health in Phenylketonuria

“…Five patients reported an intake above SAR (Table 2). Because all patients off diet showed serum concentrations within normal range, elevated serum concentrations appear to be due to fortified AAM [37]. Our findings are confirmed by the study by Stolen et al [38] reporting similar results.…”

Effect of ultrafiltered milk permeate and non-dairy creamer powder concentration on low phenylalanine yoghurt’s physicochemical properties during storage

“…In phenylketonuria patients (PKU; OMIM261600), the conversion of phenylalanine (Phe) to tyrosine is blocked, due to disruption of the activity phenylalanine hydroxylase enzyme (PAH; EC 1.14.16.1) in the liver (Wiig et al 2012). Notwithstanding, Phe is an essential amino acid and is important to ensure normal anabolism.…”