Diet principles - LC-FAOD

Dietary management of LC-FAOD:

The management of LC-FAOD consists primarily on dietary management and focusses on avoidance of prolonged fasting to prevent acute metabolic decompensation and exercise management.
Although the disorders differ, the principles of dietary management are similar, which consists of a diet low in fat, with supplementation of medium-chain triglycerides (MCT) that bypass the metabolic block, while allowing optimal nutritional status and growth by the supply of an adequate amount of protein, energy and essential (micro)nutrients.

Additionally frequent, regular feeds are recommended, especially during the first year of life. In general, most recommendations mention for infants up to 4 months of age, no fast for more than 4 hours until the first year of age, an additional hour of fasting can be added for each month. After that age for more than 12 hours should be avoided.¹

The dietary regime depends on the severity, age at onset² and the underlying disorder.

The main goals of dietary management are:^1,2,3

The dietary management will vary depending on the severity, age at onset and underlying disorder and consists of:

Prevention of catabolic stress is the most important part of the management to prevent an energy deficit, thus fasting (especially during illness) and exercise management (when energy needs are increased) to prevent accumulation of toxic intermediates
The maximum fasting period depends on age and weight.
in severe defects restricting the intake of dietary fat (that consists predominantly from long-chain fatty acids)
- LCT should be restricted in the more severe LC-FAOD, and substituted by MCT.
- Monogen is specifically targeted to symptomatic infants.
- The safe upper limit for long chain fat intake is unknown and varies with the severity of the disorder.

MTFP, LCHAD and severe phenotypes in VLCHAD

Carbohydrate-enriched diet: 60-65% of total calories
10 – 15% energy from protein
Total fat restriction 25-30 % of total calories;
- 20 – 25 En % MCT;
- 5 – 10 En % LCT
Regular meals ensuring frequent feeding with an increased carbohydrate intake and supplements of MCT.

Mild VLCAD phenotypes:

Total fat restriction max 30 % of total calories;
- 15 En % MCT;
- 15 En % LCT
Regular meals, normal overnight fasting tolerance
- Dietary fat restriction is not indicated in mild LCHAD, recently identified by New Born Screening.

Dietary management during acute exacerbations includes hydration, high-dose glucose, bed rest, urine alkalization, and carnitine supplementation. Long-term management includes a high-carbohydrate diet, medium-chain triglyceride supplementation, and avoidance of fasting and strenuous exercise.

References

Spiekerkoetter U, Duran M. Mitochondrial Fatty Acid Oxidation Disorders. In: Physician’s guide to the diagnosis, treatment and follow up of Inherited Metabolic Diseases 2^nd ed: Blau N. Springer Heidelberg New York 2014:247-266
Dixon M, MacDonald A, et al. Disorders Of Mitochondrial Energy Metabolism, Lipid Metabolism and Other Disorders. In: Clinical Paediatric Dietetics. 4^th ed: Shaw V. West Sussex: John Wiley & Sons Limited, 2014:588-636
Spiekerkoetter U, Lindner M, Santer R et al. Treatment recommendations in longchain fatty acid oxidation defects: consensus from a workshop. J Inherit Metab Dis,2009, 32 (4), pp. 498-505.