Oral L-citrulline supplementation enhances cycling time trial performance in healthy trained men: Double-blind randomized placebo-controlled 2-way crossover study

Abstract

BackgroundMany 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.MethodsA double-blind randomized placebo-controlled 2-way crossover study was employed. Twenty-two trained males consumed 2.4 g/day of L-citrulline or placebo orally for 7 days. On Day 8 they took 2.4 g of L-citrulline or placebo 1 h before a 4-km cycling time trial. Time taken to complete the 4 km cycle, along with power output/VO2 ratio (PO/VO2), plasma nitrite and nitrate (NOx) and amino acid levels, and visual analog scale (VAS) scores, was evaluated.ResultsL-Citrulline supplementation significantly increased plasma L-arginine levels and reduced completion time by 1.5 % (p < 0.05) compared with placebo. Moreover, L-citrulline significantly improved subjective feelings of muscle fatigue and concentration immediately after exercise.ConclusionsOral L-citrulline supplementation reduced the time take to complete a cycle ergometer exercise trial.Trial registrationCurrent Controlled Trials UMIN000014278.

Does l‐citrulline supplementation improve exercise blood flow in older adults?

“…Plasma [NOx] was not altered with Cit in the present study. Other studies in middle-aged adults have reported elevated biomarkers of NO production after chronic Cit (Schwedhelm et al 2008;Ochiai et al 2012), whereas some studies in younger adults have not (Bailey et al 2015;Suzuki et al 2016). The lack of change in plasma [NOx] in the present paper indicates that Cit was unable to augment systemic NO production; however, it is possible that Cit still had an influence on NO bioactivity within tissue.…”

“…; Suzuki et al . ). The lack of change in plasma [NOx] in the present paper indicates that Cit was unable to augment systemic NO production; however, it is possible that Cit still had an influence on NO bioactivity within tissue.…”

Effects of Citrulline Supplementation on Body Weight in Patients With Hepatobiliary Pancreatic Surgery

“…Arginine is noted for its unique benefits in improving reproductive, cardiovascular, pulmonary, renal, gastrointestinal, liver, and immune functions . Also, recent studies have proposed that citrulline enhances exercise endurance and performance in healthy adults . The beneficial effects of citrulline may stem from improvements in the arginine/nitric oxide pathway.…”

“…18 Also, recent studies have proposed that citrulline enhances exercise endurance and performance in healthy adults. 20,21 The beneficial effects of citrulline may stem from improvements in the arginine/nitric oxide pathway. Citrulline ingestion increases endothelial nitric oxide synthesis and may improve endothelial function.…”

A 4-week oral gavage toxicity study of L-citrulline in rats

“…To date, we have already reported some clinical utilities of the supplemented L-citrulline, focusing on the prevention of vascular dysfunction and the functional regulation of arterial stiffness (Ochiai et al, 2012;Morita et al, 2013;Morita et al, 2015). Recently, L-citrulline has also been used as a popular supplement among athletes, because L-citrulline exerts some physiological effects related to exercise performance in humans (Suzuki et al, 2016).…”