University of Nottingham, Department of Sports and Exercise Medicine, Faculty of Medicine and Health Sciences, Nottingham, UK.
J Int Soc Sports Nutr. 2023 Dec;20(1):2209056. doi: 10.1080/15502783.2023.2209056.
Citrulline is a popular dietary supplement, primarily thought to exert ergogenic effects on exercise performance through the enhancement of nitric oxide (NO) synthesis and ammonia buffering. However, recent findings surrounding citrulline's effect on endurance performance have been inconsistent. A systematic review and meta-analysis of the relevant literature have yet to be undertaken.
To determine if acute ingestion of citrulline has an ergogenic effect on endurance performance in young healthy adults.
A systematic search of three databases was undertaken to find peer-reviewed randomized controlled trials (RCTs) published in English investigating the effects of citrulline supplementation on endurance performance in young healthy adults. Two independent investigators completed a three-phased screening procedure against pre-determined eligibility criteria. Included studies evaluated loading or bolus dosage regimes of citrulline in participants aged 18 or over that were at least recreationally active. Outcome measures focused on time-to-completion (TTC) or time-to-exhaustion (TTE) in continuous submaximal intensity exercise. Cochrane's Risk of Bias 2 (RoB 2) tool was used to assess the risk of bias in individual studies. Meta-analysis was conducted using a fixed-effects model to pool the weighted estimate of standardized mean differences (SMD) across studies. A chi-squared test assessed heterogeneity between studies. This review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.
Nine studies ( = 158 participants) met the eligibility criteria; five reported TTE outcomes (I = 0%, χ = 0.37, df = 4, = 0.99) and four reported TTC outcomes (I = 0%, χ = 0.46, df = 3, = 0.93), both with a low between-study heterogeneity. The results of the meta-analyses showed no significant difference in the endurance performance measures, TTE (pooled SMD = 0.03 [-0.27, 0.33]) and TTC (pooled SMD = -0.07 [-0.50, 0.15]), after acute ingestion of citrulline supplementation or a control in young healthy adults.
The current evidence suggests no significant benefit of citrulline supplementation for endurance performance. However, the small evidence base requires further research to fully evaluate this topic. Recommendations include a focus on female populations; higher continuous doses of citrulline over seven days; and TTC outcome measures over longer distances to simulate competition.
瓜氨酸是一种流行的膳食补充剂，主要通过增强一氧化氮（NO）合成和氨缓冲作用来发挥运动表现的增效作用。然而，最近关于瓜氨酸对耐力表现的影响的研究结果并不一致。尚未对相关文献进行系统评价和荟萃分析。
确定在年轻健康成年人中，急性摄入瓜氨酸是否对耐力表现有增效作用。
系统检索了三个数据库，以查找以英文发表的、调查瓜氨酸补充对年轻健康成年人耐力表现影响的同行评审随机对照试验（RCT）。两名独立的研究者按照预先确定的纳入标准完成了三阶段筛选程序。纳入的研究评估了年龄在 18 岁或以上、至少有娱乐性运动的参与者的瓜氨酸负荷或推注剂量方案。主要结局指标是连续亚最大强度运动中的完成时间（TTC）或疲劳时间（TTE）。Cochrane 偏倚风险 2（RoB 2）工具用于评估单个研究的偏倚风险。使用固定效应模型对研究间的加权标准化均数差（SMD）进行荟萃分析。卡方检验评估了研究间的异质性。本综述按照系统评价和荟萃分析的首选报告项目（PRISMA）指南进行了报告。
符合纳入标准的有 9 项研究（ = 158 名参与者）；5 项研究报告了 TTE 结局（I = 0%，χ = 0.37，df = 4， = 0.99），4 项研究报告了 TTC 结局（I = 0%，χ = 0.46，df = 3， = 0.93），两者之间的研究间异质性均较低。荟萃分析的结果显示，在年轻健康成年人中，急性摄入瓜氨酸补充剂或对照后，耐力表现测量值 TTE（汇总 SMD = 0.03 [-0.27, 0.33]）和 TTC（汇总 SMD = -0.07 [-0.50, 0.15]）均无显著差异。
目前的证据表明，瓜氨酸补充剂对耐力表现没有显著益处。然而，由于证据基础较小，需要进一步的研究来全面评估这个问题。建议包括关注女性人群；连续七天高剂量瓜氨酸；以及更长距离的 TTC 结局测量以模拟比赛。
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