Dietary Protein Requirements in Adults With Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common types of muscular dystrophy, affecting about 4 out of 100,000 individuals. The disease is characterized by progressive muscle loss (i.e., muscle atrophy) commonly affecting the face, shoulders, and upper arm muscles. The muscle loss ultimately results in reduced strength and impaired physical performance. At present there is no cure for FSHD, therefore, physicians have focused on therapeutic interventions to help alleviate these symptoms. Daily consumption of adequate amounts of dietary protein is essential to support muscle mass maintenance and overall health and function across the lifespan. However, previous research has reported inadequate protein intake in individuals with FSHD. The characteristic of progressive muscle loss in individuals with FSHD and other muscular dystrophies is ultimately due to an imbalance in the rate of muscle building (i.e., muscle protein synthesis) and muscle breakdown (i.e., muscle protein breakdown), where individuals with FSHD have been shown to have reduced rates of muscle building. As inadequate protein intake is known to result in a loss of muscle mass, strength and function, this loss may be amplified in individuals with FSHD. Dietary recommendations traditionally have been determined through nitrogen balance techniques, where the current recommended dietary allowance (RDA) for daily protein intake for adults is 0.8 g/kg/d. However, recent research indicates how the nitrogen balance technique potentially underestimates protein requirements. Therefore, there is a need to reassess current dietary recommendations in adults with FSHD in order to help support the maintenance of muscle strength and function. Recent efforts to understand protein requirements in various populations have been completed using the indicator amino acid oxidation technique (IAAO). This non-invasive method is reported to provide a robust measure of protein requirements. Due to its non-invasive nature, the IAAO method allows researchers to use this technique in individuals with FSHD, where there is currently limited work in studying this population. The purpose of this study is to measure the protein requirements in individuals with FSHD using the non-invasive IAAO technique.