Diet principles - PA/MMA

Dietary management is based, as in most disorders of amino acid metabolism, on decreasing the load of the affected pathway.

Diet principles^1,2

The aim of dietary management of MMA/PA is maintain metabolic stability and normal growth (EIMD) by providing:

adequate energy supply combined with avoidance of prolonged fasting by providing adequate energy to meet metabolic demands.
This might require tube feeding to avoid catabolism/prologned fasting, achieve nutritional adequacy
reduced intake of precursor amino acids, Valine, Isoleucine and Threonine through a restricted natural protein diet
commonly supplemented with precursor-free L-amino acid supplements (isoleucine, valine threonine and methionine), which can vary from 15 to 50% of total protein intake².
Supplementation with precursor –free amino acid supplements is not common practise in the management in MMA/PA all over the world.
A protein substitute should contain all the remaining amino acids, with additional vitamins, minerals and trace elements to ensure adequate nutrient intake and optimal growth
Provision of an emergency regimen during illness, fasting and infections, surgery or increased activity

The amount of natural protein tolerated is determined by monitoring parameters such as growth, control of acidosis, excretion of abnormal metabolites, blood amino acid levels, and testing for body protein stores.
The least restrictive dietary approach should be taken in order to avoid over-treatment and nutritional deficiencies.

Emergency treatment includes promotion of anabolism using a special high-calorie diet, transient stop of natural protein intake or of the precursor amino acids, carefully adjusted IV treatment³.

The diet for MMA/PA 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

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: 19914636
Baumgartner et al. Proposed guidelines for the diagnosis and management of methylmalonic and propionic academia. Orphanet Journal of Rare Diseased, 2014;9:130.
Kerr I, Vockley, Gibson KM. Disorders of leucine, Isoleucine and Valine Metabolism. In: Blau N (ed) Physician’s guide to the diagnosis, treatment and follow-up of inherited metabolic diseases, 2nd edition Springer Heidelberg. 2014:103-142.