Anabolic and catabolic signals: Edited by Vickie E. Baracos and Didier AttaixLong-term effects of leucine supplementation on body compositionBalage, Michèlea,b,c; Dardevet, Dominiquea,b,cAuthor Information aINRA, UMR 1019 Nutrition Humaine, Saint Genès Champanelle, France bClermont Université, UFR Médecine, UMR 1019 Nutrition Humaine, France cCRNH Auvergne, Clermont-Ferrand, France Correspondence to Dominique Dardevet, UNH Centre de Clermont-Ferrand-Theix, INRA, 63122 Saint Genès Champanelle, France Tel: +33 473 62 45 05; fax: +33 473 62 47 55; e-mail: firstname.lastname@example.org Current Opinion in Clinical Nutrition and Metabolic Care: May 2010 - Volume 13 - Issue 3 - p 265-270 doi: 10.1097/MCO.0b013e328336f6b8 Buy Metrics Abstract Purpose of review Leucine does not only serve as a substrate for protein synthesis but is also recognized as a potent signal nutrient that regulates protein metabolism. Accordingly, leucine supplementation has been suggested to develop muscle mass or prevent protein loss in several conditions characterized by muscle protein wasting. In the present review, we reported the recent results related to the effect of dietary leucine or leucine-rich amino acid mixture and proteins on whole body composition. Recent findings Although recent studies corroborate that increasing plasma leucine concentration generally induces an increase in muscle protein synthesis, long-term dietary leucine supplementation has been poorly investigated. Chronic free leucine supplementation alone did not improve lean body or muscle mass during resistance training or in elderly, whereas it was able to limit the weight loss induced by malnutrition. Contradictory data were also reported concerning the effect of leucine supplementation for weight management in obese patients. Leucine-rich amino acid mixture or proteins appeared more efficient than leucine alone to improve muscle mass and performance, suggesting the efficacy of leucine depends nevertheless on the presence of other amino acids. Summary Until now, there is no evidence that chronic leucine supplementation is efficient in promoting muscle mass or preventing protein loss during catabolic states. Further studies are required to determine the duration and nutritional conditions of long-term leucine supplementation and to establish whether such nutritional interventions can help to prevent or treat muscle loss in various pathological or physiological conditions. © 2010 Lippincott Williams & Wilkins, Inc.