English translation of the study:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5368575/
The study published in the "Journal of Nutrition" in April 2017 explores the relative effectiveness of arginine and citrulline supplementation in increasing systemic arginine availability in mice. Arginine is an amino acid considered essential in various demanding physiological or pathological conditions, but its dietary supplementation has disadvantages, including significant extraction during the first metabolic pass. Citrulline, converted in vivo exclusively to arginine, could be a better alternative.
The objective of this research was to determine the relative effectiveness of arginine and citrulline supplementation in improving arginine availability. Six-week-old male C57BL/6J mice equipped with gastric catheters were adapted to one of 7 experimental diets, containing different levels of L-arginine or L-citrulline supplementation, for 2 weeks. Results show that all supplemented citrulline appeared in plasma and resulted in a marginal 86% increase in arginine flux, while supplemented arginine underwent ~70% extraction in the first pass, indicating that only 30% of the supplemented arginine entered the peripheral circulation. Furthermore, supplemental citrulline increased plasma arginine concentrations to a greater extent (35%, P < 0.01) than arginine supplementation.
The main conclusion of the study is that citrulline supplementation is more effective in increasing arginine availability than arginine supplementation itself in mice, which may suggest implications for nutritional interventions in humans, particularly in conditions requiring an increase in arginine availability.