Fatty acid oxidation disorders are defined by a defect in the fatty acid oxidation pathway. An inability to mobilize fatty acids for energy and a restriction in the breakdown of fats of specific lengths are hallmarks of these genetic disorders. Standard treatment of fatty acid oxidation disorders is by way of medical nutrition therapy. However, fatty acid oxidation disorders encompass a large and diverse number of disorders and treatment and management pose a unique challenge to metabolic dietitians.
With an increasing number of affected individuals being identified, it is essential that nutrition intervention be initiated as soon as a diagnosis is established. A recent study by two researchers from Emory University surveyed metabolic dietitians across the United States to determine nutritional strategies currently employed for the treatment of fatty acid oxidation disorders.
A survey was sent to all members of the PNO-METAB-L listserv, which includes metabolic dietitians throughout the United States. Questions were asked regarding nutrient composition of total diet, use of specialized formulas or lipid preparations including dose and frequency and parameters used to monitor dietary management and disease progression. The same questions were asked for each of three disease categories: medium-chain Acyl-CoA dehydrogenase deficiency (MCAD); very-long-chain Acyl-CoA dehydrogenase deficiency (VLCAD); and a third category that combined long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHAD), long-chain Acyl-CoA dehydrogenase deficiency (LCAD) and trifunctional protein deficiency (TFP).
Forty-nine dietitians returned the survey. Twenty-five reported no patients in their practice with fatty acid oxidation disorders and 24 reported interaction with current or past patients with these disorders. The 24 informative respondents represented information regarding 200 individual patients with fatty acid oxidation disorders including 114 patients with MCAD, 26 with VLCAD, 23 with LCHAD or TFP and 37 patients in the `other' category. All 24 dietitians reported prescribing an increased frequency of meals. Fourteen dietitians reported prescribing cornstarch, with the highest use in patients with LCHAD and TFP. Cornstarch is administered to minimize fasting intolerance in affected individuals, especially during sleeping hours or before intense activity. Twenty respondents prescribed carnitine as a supplement; the majority of carnitine usage was in patients with MCAD, LCHAD and TFP with the median dose being 75 mg/kg/day. Twenty-two dietitians reported restricting fat intake of patients with these disorders. The median fat restriction was 29% of the diet, with a range of 10 to 35%. Fourteen of the respondents reported prescribing medical formulas to provide a diet low in fat and yet dense in all other nutrients, while 16 reported supplementation with specific oils including flaxseed, canola, walnut, or safflower oil.
Current standard of care appears to focus on fat restriction and increased meal frequency with the increasing use of cornstarch and/or carnitine supplementation. The clinical efficacy of medium-chain triglyceride oil, other lipid substrates and medical foods requires further study for the development of standardized treatment and monitoring strategies and product formulations tailored to the needs of patients with fatty acid oxidation disorders.
Java O. Solis and Rani H. Singh, Management of fatty acid oxidation disorders: a survey of current treatment strategies, JADA 102(12): 1800-1806 (December 2002) [Address correspondence to: Rani H. Sing, Emory University, Department of Pediatrics, Division of Medical Genetics, 2040 Ridgewood Dr, NE, Atlanta, GA 30322. E-mail: email@example.com]
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