Compendium of the most significant studies with reference to properties, intake, effects.

Gonzalez AM, Trexler ET. Effects of Citrulline Supplementation on Exercise Performance in Humans: A Review of the Current Literature. J Strength Cond Res. 2020 May;34(5):1480-1495. doi: 10.1519/JSC.0000000000003426. 

Abstract. Over the past decade, L-citrulline has received considerable scientific attention examining potentially ergogenic properties for both aerobic and anaerobic exercise performance. Thus, the purpose of this article is to summarize the theoretical rationale behind L-citrulline supplementation and to comprehensively review the available scientific evidence assessing the potential ergogenic value of L-citrulline supplementation on vascular function and exercise performance in humans. In addition, research that has investigated the potential synergistic effects of L-citrulline with other dietary ingredients (e.g., arginine, antioxidants, nitrates, and branched-chain amino acids) is reviewed. 

Jirka A, Layec S, Picot D, Bernon-Ferreira S, Grasset N, Flet L, Thibault R, Darmaun D. 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. Clin Nutr. 2019 Dec;38(6):2599-2606. doi: 10.1016/j.clnu.2018.12.030.

Abstract. The aim of the study was to determine whether citrulline impacts whole body protein metabolism in patients with short bowel syndrome

Suzuki T, Morita M, Kobayashi Y, Kamimura A. Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study. J Int Soc Sports Nutr. 2016 Feb 19;13:6. doi: 10.1186/s12970-016-0117-z. 

Abstract. Many human studies report that nitric oxide (NO) improves sport performance. This is because NO is a potential modulator of blood flow, muscle energy metabolism, and mitochondrial respiration during exercise. L-Citrulline is an amino acid present in the body and is a potent endogenous precursor of L-arginine, which is a substrate for NO synthase. Here, we investigated the effect of oral L-citrulline supplementation on cycling time trial performance in humans.

Figueroa A, Wong A, Jaime SJ, Gonzales JU. Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance. Curr Opin Clin Nutr Metab Care. 2017 Jan;20(1):92-98. doi: 10.1097/MCO.0000000000000340. 

Abstract. L-Citrulline, either synthetic or in watermelon, may improve vascular function through increased L-arginine bioavailability and nitric oxide synthesis. This article analyses potential vascular benefits of L-citrulline and watermelon supplementation at rest and during exercise.

Khalaf D, Krüger M, Wehland M, Infanger M, Grimm D. The Effects of Oral l-Arginine and l-Citrulline Supplementation on Blood Pressure. Nutrients. 2019 Jul 22;11(7):1679. doi: 10.3390/nu11071679.

Abstract. Nitric oxide (NO) is a well-known vasodilator produced by the vascular endothelium via the enzyme endothelial nitric oxide synthase (eNOS). The inadequate production of NO has been linked to elevated blood pressure (BP) in both human and animal studies, and might be due to substrate inaccessibility. This review aimed to investigate whether oral administration of the amino acids l-arginine (Arg) and l-citrulline (Cit), which are potential substrates for eNOS, could effectively reduce BP by increasing NO production.

Joshi V, Joshi M, Silwal D, Noonan K, Rodriguez S, Penalosa A. Systematized biosynthesis and catabolism regulate citrulline accumulation in watermelon. Phytochemistry. 2019 Jun;162:129-140. doi: 10.1016/j.phytochem.2019.03.003.

Abstract. To understand the regulation of citrulline accumulation, we investigated the expression of genes associated with its biosynthesis and catabolism in flesh and rind tissues during fruit development. 

Hwang P, Morales Marroquín FE, Gann J, Andre T, McKinley-Barnard S, Kim C, Morita M, Willoughby DS. Eight weeks of resistance training in conjunction with glutathione and L-Citrulline supplementation increases lean mass and has no adverse effects on blood clinical safety markers in resistance-trained males. J Int Soc Sports Nutr. 2018 Jun 27;15(1):30. doi: 10.1186/s12970-018-0235-x.

Abstract. Supplementation of combined glutathione (GSH) with L-citrulline in response to a single bout of resistance exercise has been shown to increase plasma nitric oxide metabolites, nitrite and nitrate and cyclic guanosine monophosphate (cGMP), which may play a role in muscle protein synthesis. As a result, in response to resistance training (RT) these responses may establish a role for GSH + L-citrulline to increase muscle mass. This study attempted to determine the effects of an 8-week RT program in conjunction with GSH (Setria®) + L-citrulline, L-citrulline-malate, or placebo supplementation on lean mass and its association with muscle strength. The secondary purpose was to assess the safety of such supplementation protocol by assessing clinical chemistry markers.

Darrah E, Andrade F. Rheumatoid arthritis and citrullination. Curr Opin Rheumatol. 2018 Jan;30(1):72-78. doi: 10.1097/BOR.0000000000000452.

Abstract. Dysregulated citrullination is a key element that drives the production and maintenance of antibodies to citrullinated proteins, a hallmark in rheumatoid arthritis (RA). This article reviews recent literature on the origin of citrullinated antigens in RA.

Romero MJ, Platt DH, Caldwell RB, Caldwell RW. Therapeutic use of citrulline in cardiovascular disease. Cardiovasc Drug Rev. 2006 Fall-Winter;24(3-4):275-90. doi: 10.1111/j.1527-3466.2006.00275.x.

Abstract. L-citrulline is the natural precursor of L-arginine, substrate for nitric oxide synthase (NOS) in the production of NO. Supplemental administration L-arginine has been shown to be effective in improving NO production and cardiovascular function in cardiovascular diseases associated with endothelial dysfunction, such as hypertension, heart failure, atherosclerosis, diabetic vascular disease and ischemia-reperfusion injury, but the beneficial actions do not endure with chronic therapy.