Nutrients (Dec 2022)

UK Dietary Practices for Tyrosinaemias: Time for Change

  • Anne Daly,
  • Sarah Adam,
  • Heather Allen,
  • Jane Ash,
  • Clare Dale,
  • Marjorie Dixon,
  • Carolyn Dunlop,
  • Charlotte Ellerton,
  • Sharon Evans,
  • Sarah Firman,
  • Suzanne Ford,
  • Francine Freedman,
  • Joanna Gribben,
  • Sara Howe,
  • Farzana Khan,
  • Joy McDonald,
  • Nicola McStravick,
  • Patty Nguyen,
  • Natalia Oxley,
  • Rachel Skeath,
  • Emma Simpson,
  • Allyson Terry,
  • Alison Woodall,
  • Lucy White,
  • Anita MacDonald

DOI
https://doi.org/10.3390/nu14245202
Journal volume & issue
Vol. 14, no. 24
p. 5202

Abstract

Read online

In the UK, different dietary systems are used to calculate protein or tyrosine/phenylalanine intake in the dietary management of hereditary tyrosinaemia, HTI, II and III (HT), with no systematic evidence comparing the merits and inadequacies of each. This study aimed to examine the current UK dietary practices in all HTs and, using Delphi methodology, to reach consensus agreement about the best dietary management system. Over 12 months, five meetings were held with UK paediatric and adult dietitians working in inherited metabolic disorders (IMDs) managing HTs. Eleven statements on the dietary system for calculating protein or tyrosine/phenylalanine intake were discussed. Dietitians from 12 of 14 IMD centres caring for HT patients participated, and 7/11 statements were agreed with one Delphi round. Nine centres (three abstentions) supported a 1 g protein exchange system for all foods except fruit and vegetables. The same definitions used in the UK for phenylketonuria (PKU) were adopted to define when to calculate foods as part of a protein exchange system or permit them without measurement. Fruit and vegetables contain a lower amount of tyrosine/phenylalanine per 1 g of protein than animal and cereal foods. The correlation of tyrosine vs. phenylalanine (mg/100 g) for vegetables and fruits was high (r = 0.9). In Delphi round 2, agreement was reached to use the tyrosine/phenylalanine analyses of fruits/vegetables, for their allocation within the HT diet. This allowed larger portion sizes of measured fruits and vegetables and increased the variety of fruit and vegetables that could be eaten without measurement. In HTs, a combined dietary management system will be used: 1 g protein exchanges for cereal and milk protein sources and tyrosine/phenylalanine exchanges for fruit and vegetables. Intensive, systematic communication with IMD dietitians and reappraisal of the evidence has redefined and harmonised HT dietary practice across the UK.

Keywords