Preliminary Data on Free Use of Fruits and Vegetables Containing Phenylalanine 76–100 mg/100 g of Food in 16 Children with Phenylketonuria: 6 Months Follow-Up

Abstract

In phenylketonuria (PKU), a previous intervention study assessing the patients ability to tolerate fruits and vegetables containing phenylalanine 76–100 mg/100 g without limit or measurement, found that an extra 50 mg/day phenylalanine, but not 100 mg/day, was tolerated from these fruits and vegetables. In a further 6-month extension study, we examined the effect of the ‘free’ use of this group of fruits and vegetables on blood phenylalanine control. For 6 months, the patients ate fruits and vegetables containing phenylalanine 76–100 mg/100 g without limit or measurement. Three-day diet diaries and the patients’ weights were collected monthly. Blood phenylalanine spots were collected weekly aiming for blood phenylalanine levels <360 μmol/L. Retrospective blood phenylalanine was collected 6 months pre-trial. All 16 patients (69% females) from the intervention study took part in the extension study. Most of the patients (n = 14/16) had classical PKU with a median age of 10.5 years (range: 6–13). There was no statistically significant difference in the median blood phenylalanine pre-study (270, range: 50–760 μmol/L) compared to the 6-month extension study (250, range: 20–750 μmol/L) (p= 0.4867). The patients had a median of 21 and 22 bloodspots, pre- and post-trial, respectively. In the extension study, the patients had an actual mean intake of 11 g/day (4–37) natural protein and 65 g/day (60–80) protein equivalent from a protein substitute. The mean phenylalanine intake was 563 mg/day (200–1850) with only 19 mg/day (0–146) phenylalanine from fruits and vegetables containing phenylalanine 76–100 mg/100 g. The weight z-scores remained unchanged (1.52 vs. 1.60, p = 0.4715). There was no adverse impact on blood phenylalanine control when fruits and vegetables containing phenylalanine 76–100 mg/100 g were eaten without limit or measurement. However, the fruits and vegetable portion sizes eaten were small (60 g/week). Further longitudinal work is necessary to examine the ‘free’ use of fruits and vegetables containing phenylalanine 76–100 mg/100 g on metabolic control in patients with PKU.