The Study
Effect of oral citrulline supplementation on whole body protein metabolism in adult patients with short bowel syndrome: A pilot, randomized, double-blind, cross-over study.
This study gave people with a short intestine either citrulline or a fake pill, then measured what happened to their body’s protein. It found citrulline raised certain chemicals in the blood, but didn’t make their muscles build more protein — unless their citrulline was already super low. So it shows what happened in this small group, but doesn’t prove it works for everyone.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Scientists gave people with very short intestines a daily citrulline pill to see if it helped their bodies make more protein. It raised certain amino acids in the blood but didn’t change overall protein building — unless their citrulline levels were very low to start with.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 558 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1For most people with short bowel syndrome who are already well-nourished, citrulline doesn’t help build muscle.
- 2But for those with severe citrulline deficiency, it might.
- 3Citrulline raised blood citrulline by 17x and arginine by 3x.
- 4Protein synthesis didn’t change overall (p=0.36).
- 5In 3 people with very low citrulline (<20 μmol/L), protein synthesis went up.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Clinical nutrition
Year
2019
Authors
A. Jirka, S. Layec, D. Picot, S. Bernon-Ferreira, N. Grasset, L. Flet, R. Thibault, D. Darmaun
Related Content
Claims (5)
Taking L-citrulline by mouth increases blood levels of L-arginine more than taking the same amount of L-arginine directly.
In adults with short bowel syndrome and about 90 cm of remaining small intestine, taking 0.18 grams of citrulline per kilogram of body weight daily for 7 days raises plasma citrulline levels 17 times and plasma arginine levels 3 times, without changing overall protein synthesis rates.
In adults with short bowel syndrome and low blood citrulline levels, taking citrulline by mouth increases the rate at which leucine is used for building proteins rather than being burned for energy.
Taking 0.18 grams of citrulline per kilogram of body weight daily for seven days does not change how the body uses leucine to build protein, break down leucine for energy, or release leucine into the bloodstream in adults with short bowel syndrome who have normal citrulline levels and are in the later stage of gut recovery.
Taking citrulline by mouth does not change the levels of insulin or IGF-1 in the blood of adults with short bowel syndrome.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.