Essential amino acids help cystic fibrosis patients
Essential amino acids help cystic fibrosis patients

Dietary Essential Amino Acids Are Highly Anabolic in Pediatric Patients with Cystic Fibrosis


Patients with cystic fibrosis (CF) are prone to muscle wasting due to factors such as lack of adequate protein, systemic inflammation, and hormonal changes. Maintaining muscle mass in individuals with CF helps ensure better survival rates, supports lung and muscle function, and protects bone mineral density. 

Conventional nutritional approaches have been unable to promote muscle gain in CF patients. Because amino acid supplements have been proven to stimulate muscle protein synthesis in populations prone to muscle wasting, researchers set out to examine if a similar effect could be achieved in pediatric patients with cystic fibrosis. 

Trial Length

2 days

Number of Subjects

10 - 21


All genders

Age Range

10 - 21

The Goal

Previous research shows that essential amino acids (EAAs) are able to stimulate muscle protein synthesis 2 times more than whey protein and that when leucine makes up 40% of the EAAs the muscle-building effects are even greater. Leucine is also known to help improve the insulin response, which is suppressed in CF patients. Researchers were also curious about the effects of the nonessential amino acid arginine on nitric oxide, which is reduced in CF patients. 

For this reason, researchers studied the muscle-building effects of a leucine-enriched EAA formula compared to a balanced mixture of essential and nonessential amino acids in whey protein. They also compared the effects of the two mixtures on the production of arginine and the nitric oxide synthesis rate to determine if a formula of free amino acids can help prevent or improve muscle wasting in CF patients as a means of decreasing morbidity and mortality.

The Results

The mixture of essential amino acids stimulated muscle protein synthesis and suppressed muscle protein breakdown to a greater degree than did the balanced whey mixture of essential and nonessential amino acids. Arginine production was lower in the EAA group, but nitric oxide synthesis was similar.Net protein synthesis is improved in patents with cystic fibrosis taking essential amino acids.


Researchers concluded that an EAA mixture is preferred to dietary protein intake, as only the EAAs are needed to activate a high anabolic response, and that the addition of arginine or citrulline (a precursor of arginine) to the EAA supplement may be advised as an alternative to high leucine content, which may not be needed in CF.  

High leucine content may be unnecessary

The addition of leucine to the EAA mixture did not have further muscle-building effects. Researchers theorize that reducing the leucine content and making way for other essential amino acids or arginine may increase the anabolic response in CF patients. 

The Why?

Muscle wasting is present in up to 30% of cystic fibrosis patients and leads to bone mineral loss, reduced lung capacity, and lower quality of life. An essential amino acid supplement offers an alternative to conventional nutritional approaches that have proven ineffective at promoting muscle gain in CF patients. 


Engelen MP, Com G, Wolfe RR, Deutz NE. Dietary essential amino acids are highly anabolic in pediatric patients with cystic fibrosis. J Cyst Fibros. 2013;12(5):445-453. doi:10.1016/j.jcf.2012.12.011