The Impact of Nutritional Management on Fat-Soluble Nutrient Status in Patients with Fatty Acid Oxidation Disorders:...

Background: Fatty acid oxidation disorders (FAOD) are rare inborn errors of metabolism that impair mitochondrial β-oxidation and energy production. Management includes fasting avoidance for all FAOD types. Patients with long-chain FAOD are advised to restrict long-chain triglycerides (LCTs) to 10% of total energy intake and supplement medium-chain triglycerides (MCTs). The impact of such dietary modification on fat-soluble vitamin status has not yet been studied. Methods: In this cross-sectional study, serum concentrations of vitamins A, 25(OH)D, E, and β-carotene were measured in 36 FAOD patients and 36 healthy controls matched for age and sex. Vitamins A, E, and β-carotene were quantified using high-performance liquid chromatography and vitamin 25(OH)D through an immunoassay. FAOD patients were further divided into fat-modified (LCT-restricted) and standard-fat diet subgroups based on dietary management. Results: FAOD patients had significantly higher vitamin A concentrations than controls (p < 0.05), while there was no difference in vitamins 25(OH)D, E, and β-carotene. Within the FAOD cohort, the fat-modified group had higher levels of vitamins A and 25(OH)D but lower levels of vitamin E and β-carotene than the standard-fat group (all p < 0.05). Vitamin 25(OH)D deficiency (<20 ng/mL) was more frequent in the standard-fat group (p = 0.03). Conclusions: Fat-modified diets influence fat-soluble vitamin status in FAOD, emphasising the importance of ongoing monitoring and tailored supplementation. Future work should focus on optimising nutritional management, including modifications to formula composition, and on addressing the currently limited evidence on nutritional status and vitamin deficiencies in patients with FAOD.