Diet principles - UCD

Dietary managing is based on minimizing the nitrogen load on the urea cycle, but adapting the level of natural protein to individual tolerance against ammonia.

Most patients require a restricted natural protein intake, which can be different in each patient and can be as low as the minimum required level to maintain optimal growth. This restriction can be adequate but must be monitored frequently to prevent growth impairment and metabolic instability¹ and inadequate micronutrient intake.
If the intake is below safe levels of protein intake² an essential amino acid supplementation is indicated.
Next, an adequate supply of energy has to be provided to prevent catabolism and consequently metabolic instability by hyperammonemia. To ensure sufficient energy and protein intake, tube feeding might be necessary.

Chronic management includes a strict dietary regime based on a natural protein restriction, providing adequate energy intake and supplementation of essential amino acids and other (micro) nutrients.

Diet principles^3,4

Restriction of natural protein intake, supplementation of an essential L-amino acid supplement, if protein intake is below the minimum safe level of protein intake
Ensure adequate energy provision to ensure
Providing scavenger medication to utilize alternative pathways to the urea cycle for excretion of waste nitrogen
Proving arginine supplements to increase the flux through the urea cycle and as substrate for production of arginine metabolites
Ensure adequate micronutrient intake
Ensure a emergency protocol during intercurrent illness, fasting and infections, surgery or increased activity

The diet for UCD patients must be individualized depending on each patient’s nutrient and growth requirements. The amount of natural protein allowed in the diet depends on the patient’s metabolic status, anabolism and growth velocity. Close monitoring is essential.

References

Häberle et al. Suggested guidelines for the diagnosis and management of urea cycle disorders. Orphanet Journal of Rare Diseases 2012;7:32
WHO Technical Report series: Protein and amino acid requirement in human nutrition. In report of a joint WHO/FAO/UNU expert consultation series 935;2007.
Dixon M, MacDonald A, White F, Stafford J. Disorders of Amino Acid Metabolism, Organic Acidaemias and Urea Cycle Disorders. In: Clinical Paediatric Dietetics. 4^th ed: Shaw V. West Sussex: John Wiley & Sons Limited, 2014:381-525
E-IMD. Urea cycle disorders: quick reference guide. http://www.e-imd.org.