High carb diet useful for muscle disorder

NEW YORK (Reuters Health) - A diet high in carbohydrate instead of protein improves the ability of people with McArdle disease to exercise, results of a small study indicate.

McArdle disease is a metabolic muscle disorder. People born with the disease are unable to produce an enzyme called muscle phosphorylase, which is important in producing the fuel source required by the muscles for exercise.

People with McArdle disease develop severe muscle pain and fatigue in the first few minutes of exercise, followed often by severe muscle spasms if they continue to exercise.

Two small studies have suggested that a protein-rich diet may be beneficial for patients with McArdle disease.

In the current study, Drs. S. T. Andersen and J. Vissing, from the University of Copenhagen, Denmark examined the effects of a carbohydrate-rich versus a protein-rich diet on exercise "tolerance" in 7 adults with McArdle disease.

The patients were randomized to follow one diet or the other diet for 3 days. The patients exercised on a stationary bicycle after each diet.

The investigators found that exercise performance was better with the carbohydrate-rich diet than the protein-rich diet. For example, heart rate and perceived exertion were consistently lower and maximal oxygen uptake was 25 percent higher in patients on the carbohydrate versus the protein diet.

This study, Andersen and Vissing conclude, suggests that patients with McArdle disease should be kept on a diet with a high content of carbohydrates to improve their ability to tolerate exercise.

SOURCE: Journal of Neurology, Neurosurgery, and Psychiatry, December 2008.