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Changes in serum phenylalanine after overnight fasts in youngsters with phenylketonuria

Lookup NU author(s): Dr Andrew Morris


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Background and aims:In patients with phenylketonuria (PKU), overnight fasting is associated with rises in serum phenylalanine [PHE) concentration. This is thought to result from catabolism of endogenous protein, which can be reduced by a bedtime snack accompanied by a dose of PHE-free protein substitute (P/S). This study assessed the effectiveness of this strategy and whether any additional benefit was conferred by omitting PHE from the bedtime snack. Methods: Data are presented for 18 PKU children (aged 9-16 years), studied over a 48-h period whilst following diets of known composition. All the subjects had a bedtime snack accompanied by 25% of their P/S daily requirement. Half the subjects (Group X) had 25% of their daily PHE allowance in the bedtime snack, whilst the others [Group Z) ate only 'PHE-free' foods at this time. Results: Overnight changes in serum PHE levels were generally small for both groups; the mean serum PHE level changed very little overnight (Group X: 405 mu mol L-1 post snack, 389 mu mol L-1 prebreakfast; Group Z: 430 mu mol L-1 post snack, 426 mu mol L-1 pre breakfast). Conclusion: Overnight changes in serum PHE levels can be minimized by a bedtime snack accompanied by a proportion of the daily protein substitute. Omission of PHE from the snack confers no extra advantage.

Publication metadata

Author(s): Ferguson C, Morris AM

Publication type: Article

Publication status: Published

Journal: Journal of Human Nutrition and Dietetics

Year: 1999

Volume: 12

Issue: 3

Pages: 213-218

Print publication date: 01/06/1999

ISSN (print): 0952-3871

ISSN (electronic): 1365-277X

Publisher: Wiley-Blackwell Publishing Ltd.


DOI: 10.1046/j.1365-277x.1999.00158.x


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