{"@context":"https://schema.org","@type":"DietarySupplement","id":"https://nutripedia.co.uk/items/l-citrulline","url":"https://nutripedia.co.uk/items/l-citrulline","name":"L-Citrulline","category":"Performance","tagline":"Boosts nitric oxide for better blood flow and exercise performance.","verdict":"promising","evidenceRating":3,"verdictSummary":"Growing evidence for improved exercise performance and reduced fatigue. More effective than supplementing L-arginine directly.","dosage":{"recommended":"6–8","unit":"g","timing":"30–60 minutes before exercise","notes":"Citrulline malate (2:1 ratio) is the most studied form."},"keyBenefits":["Increases nitric oxide and blood flow","May reduce muscle soreness post-exercise","Supports both aerobic and anaerobic performance"],"warnings":["May interact with blood pressure medications","High doses can cause gastrointestinal discomfort"],"evidenceSummary":null,"dosing":null,"safety":null,"whoMightBenefit":[],"whoShouldAvoid":[],"regulatoryNotes":null,"faqs":[{"question":"Why is l-citrulline considered more effective than l-arginine for raising nitric oxide?","answer":"A pharmacokinetic crossover study (Schwedhelm et al., 2008, PMID: 17922905) found that oral l-citrulline raised plasma arginine significantly more than an equivalent dose of l-arginine at 3–8 h post-ingestion, and increased urinary nitric oxide metabolite excretion by 39% more than arginine. This is because l-arginine undergoes extensive first-pass catabolism in the gut and liver by arginase enzymes, while l-citrulline bypasses these pathways and is converted to l-arginine in the kidneys, providing a more sustained elevation of arginine bioavailability."},{"question":"What is the difference between l-citrulline and citrulline malate?","answer":"Citrulline malate is l-citrulline bound to malic acid in a 2:1 (citrulline:malate) ratio. Malic acid is an intermediate in the Krebs cycle and is proposed to contribute to energy production and ammonia clearance independently of citrulline. The majority of performance trials have used citrulline malate at 6–8 g (providing approximately 4–5 g of l-citrulline). Whether the malate component contributes to the observed benefits is not established: no controlled trial has compared equimolar free citrulline to citrulline malate using matched citrulline content."},{"question":"What doses have trials used to test exercise performance?","answer":"Performance trials have most commonly used a single acute dose of 6–8 g of citrulline malate, taken 60 minutes before exercise. In one frequently cited RCT (Pérez-Guisado & Jakeman, 2010, PMID: 20386132), participants received 8 g of citrulline malate one hour prior to a high-volume flat bench press protocol. Chronic dosing protocols in the blood pressure literature have used 3–6 g/day of l-citrulline for 4–8 weeks. There is no established single 'optimal' dose — the evidence base spans both acute and chronic administration."},{"question":"Is the evidence for l-citrulline consistent across exercise types?","answer":"The evidence is heterogeneous. A 2010 crossover RCT reported a 52.92% increase in total bench press repetitions with 8 g of citrulline malate vs placebo (PMID: 20386132). However, a 2019 RCT found no significant benefit in a German Volume Training resistance protocol (PMID: 30817540). Cycling trials have shown small positive effects. The inconsistency may relate to differences in exercise type, participant training status, dosing protocols, and whether acute or chronic supplementation was studied."},{"question":"Does l-citrulline affect blood pressure?","answer":"Trials have reported modest reductions in systolic blood pressure, primarily in individuals with prehypertension or hypertension. In one crossover RCT, watermelon extract providing approximately 6 g/day of citrulline reduced ankle systolic blood pressure by 9 mmHg over 6 weeks (Figueroa et al., 2011, PMID: 21067832). A 2018 systematic review concluded the effect was consistent in hypertensive but not normotensive participants. Individuals taking antihypertensive medication should be aware of potential additive effects on blood pressure."},{"question":"Are there reported adverse events from l-citrulline supplementation?","answer":"Reported adverse events across published trials have been limited to mild gastrointestinal discomfort at high single doses (>10 g), including nausea and stomach upset. No serious adverse events have been reported in controlled trials. Individuals taking antihypertensive or erectile dysfunction medications (which also affect nitric oxide or vasodilation pathways) should consult a healthcare professional before use, as additive blood pressure-lowering effects are plausible."},{"question":"Does l-citrulline reduce muscle soreness?","answer":"Some trials have reported reductions in delayed-onset muscle soreness (DOMS). In one crossover RCT (PMID: 20386132), participants reported 40% less soreness at 24 and 48 hours post-exercise after receiving 8 g of citrulline malate. However, a 2019 RCT specifically designed to test this in a high-volume resistance protocol found no significant effect on muscle soreness (PMID: 30817540). The evidence for DOMS reduction is therefore inconsistent and should not be relied upon as a primary reason for supplementation."}],"research":{"totalCount":15,"papers":[{"title":"Does l-citrulline supplementation and watermelon intake reduce blood pressure in middle-aged and older adults? A systematic review and meta-analysis of randomized controlled trials","year":2025,"journal":"Clinical Nutrition ESPEN","doi":"10.1016/j.clnesp.2025.07.1130","pmid":"40789388","url":"https://doi.org/10.1016/j.clnesp.2025.07.1130","studyDesign":"meta-analysis","fields":[],"conclusion":"Meta-analysis of 15 RCTs (415 participants, 24 datasets) found l-citrulline and watermelon intake significantly reduced systolic BP by 4.02 mmHg and diastolic BP by 2.54 mmHg in middle-aged and older adults. Combined L-citrulline + L-arginine was superior to either intervention alone, suggesting additive cardiovascular benefit.","abstract":"","citationCount":0},{"title":"Citrulline in the management of patients with urea cycle disorders","year":2023,"journal":"Orphanet Journal of Rare Diseases","doi":"10.1186/s13023-023-02800-8","pmid":"37480106","url":"https://doi.org/10.1186/s13023-023-02800-8","studyDesign":"cohort","fields":[],"conclusion":"Retrospective analysis of 79 urea cycle disorder patients showed citrulline supplementation (alone or with arginine) effectively controlled ammonia levels, with citrulline monotherapy achieving lower mean ammonia (35.9 µmol/L) than arginine alone (49.8 µmol/L). Citrulline is the preferred single-agent option for raising plasma arginine.","abstract":"","citationCount":0},{"title":"Effects of citrulline on endurance performance in young healthy adults: a systematic review and meta-analysis","year":2023,"journal":"Journal of the International Society of Sports Nutrition","doi":"10.1080/15502783.2023.2209056","pmid":"37155582","url":"https://doi.org/10.1080/15502783.2023.2209056","studyDesign":"meta-analysis","fields":[],"conclusion":"Analysis of 9 RCTs (158 participants) found no significant difference in endurance performance (time-to-exhaustion or time-to-completion) following citrulline supplementation vs placebo. Authors recommend further research with higher doses, longer loading periods, and female-inclusive populations before conclusions can be drawn.","abstract":"","citationCount":0},{"title":"Effects of Citrulline Supplementation on Different Aerobic Exercise Performance Outcomes: A Systematic Review and Meta-Analysis","year":2022,"journal":"Nutrients","doi":"10.3390/nu14173479","pmid":"36079738","url":"https://doi.org/10.3390/nu14173479","studyDesign":"meta-analysis","fields":[],"conclusion":"Meta-analysis of 10 controlled trials found no significant benefit of citrulline supplementation on aerobic exercise performance, RPE, VO2 kinetics, or blood lactate compared to placebo (pooled SMD = 0.15, p = 0.08). Current evidence does not support citrulline for aerobic performance enhancement.","abstract":"","citationCount":0},{"title":"Effects of Citrulline Malate Supplementation on Muscle Strength in Resistance-Trained Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials","year":2022,"journal":"Journal of Dietary Supplements","doi":"10.1080/19390211.2021.1939473","pmid":"34176406","url":"https://doi.org/10.1080/19390211.2021.1939473","studyDesign":"meta-analysis","fields":[],"conclusion":"Meta-analysis of 4 RCTs (138 assessments) found no significant effect of citrulline malate on upper or lower body muscle strength in healthy resistance-trained individuals. Despite proposed ergogenic mechanisms, supplementation did not translate to meaningful strength gains in this population.","abstract":"","citationCount":0},{"title":"Effects of l-citrulline supplementation and watermelon consumption on longer-term and postprandial vascular function and cardiometabolic risk markers: a meta-analysis of randomised controlled trials in adults","year":2021,"journal":"British Journal of Nutrition","doi":"10.1017/S0007114521004803","pmid":"34863321","url":"https://doi.org/10.1017/S0007114521004803","studyDesign":"meta-analysis","fields":[],"conclusion":"Meta-analysis of 17 RCTs found longer-term L-citrulline supplementation significantly improved brachial artery flow-mediated vasodilation (FMD) by 0.9 percentage points (p < 0.001). Watermelon consumption improved pulse wave velocity. No postprandial effects on vascular function were detected. Suggests a cardiovascular benefit with sustained supplementation.","abstract":"","citationCount":0},{"title":"Acute L-Citrulline Supplementation Increases Nitric Oxide Bioavailability but Not Inspiratory Muscle Oxygenation and Respiratory Performance","year":2021,"journal":"Nutrients","doi":"10.3390/nu13103311","pmid":"34684312","url":"https://doi.org/10.3390/nu13103311","studyDesign":"rct","fields":[],"conclusion":"Double-blind crossover RCT (12 healthy males, 6 g L-citrulline vs placebo) confirmed single-dose citrulline significantly increased exhaled nitric oxide bioavailability, but did not improve inspiratory muscle oxygenation or respiratory performance during a fatiguing incremental resistive breathing protocol.","abstract":"","citationCount":0},{"title":"A critical review of citrulline malate supplementation and exercise performance","year":2021,"journal":"European Journal of Applied Physiology","doi":"10.1007/s00421-021-04774-6","pmid":"34417881","url":"https://doi.org/10.1007/s00421-021-04774-6","studyDesign":"systematic-review","fields":[],"conclusion":"An acute 8 g dose of citrulline malate may modestly improve muscular endurance-strength performance, but evidence is inconsistent. Little support exists for benefits to power, maximal strength, or recovery. Methodological variability and product quality control issues limit interpretation across the literature.","abstract":"","citationCount":0},{"title":"Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-Analysis","year":2021,"journal":"International Journal of Sport Nutrition and Exercise Metabolism","doi":"10.1123/ijsnem.2020-0295","pmid":"34010809","url":"https://doi.org/10.1123/ijsnem.2020-0295","studyDesign":"meta-analysis","fields":[],"conclusion":"Acute citrulline malate supplementation (6–8 g, 40–60 min pre-exercise) increased repetitions to failure by ~3 reps (6.4%) vs placebo across 8 studies and 137 participants. The ergogenic effect was small but statistically meaningful, with lower body exercises showing greater benefit than upper body.","abstract":"","citationCount":0},{"title":"Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: A systematic review and meta-analysis","year":2020,"journal":"Journal of Sport and Health Science","doi":"10.1016/j.jshs.2020.02.003","pmid":"33308806","url":"https://doi.org/10.1016/j.jshs.2020.02.003","studyDesign":"meta-analysis","fields":[],"conclusion":"Across 13 RCTs (206 participants), citrulline supplementation significantly reduced post-exercise RPE and muscle soreness at 24 h and 48 h post-exercise, with no significant effect on blood lactate. Most common dose was 8 g citrulline malate. Benefits for soreness diminished by 72 h.","abstract":"","citationCount":0},{"title":"Therapeutic potential of citrulline as an arginine supplement: a clinical pharmacology review","year":2020,"journal":"Paediatric Drugs","doi":"10.1007/s40272-020-00384-5","pmid":"32140997","url":"https://doi.org/10.1007/s40272-020-00384-5","studyDesign":"systematic-review","fields":[],"conclusion":"L-citrulline demonstrates superior bioavailability over L-arginine by bypassing hepatic first-pass metabolism. Review concludes citrulline shows promise for improving NO regulation in cardiovascular disease, but optimal clinical use in paediatrics requires better-defined pharmacokinetic-pharmacodynamic relationships across developmental stages.","abstract":"","citationCount":0},{"title":"Effects of Citrulline Supplementation on Exercise Performance in Humans: A Review of the Current Literature","year":2020,"journal":"Journal of Strength and Conditioning Research","doi":"10.1519/JSC.0000000000003426","pmid":"31977835","url":"https://doi.org/10.1519/JSC.0000000000003426","studyDesign":"systematic-review","fields":[],"conclusion":"Systematic review found that L-citrulline supplementation increases plasma citrulline, arginine, and nitrate concentrations, and can enhance exercise performance and recovery. However, evidence for improved vasodilation was described as scarce and inconsistent. Investigators concluded net performance benefit exists but further research is required.","abstract":"","citationCount":0},{"title":"Effect of L-Citrulline Supplementation on Blood Pressure: a Systematic Review and Meta-Analysis of Clinical Trials","year":2018,"journal":"Current Hypertension Reports","doi":"10.1007/s11906-018-0898-3","pmid":"30284051","url":"https://doi.org/10.1007/s11906-018-0898-3","studyDesign":"meta-analysis","fields":[],"conclusion":"Meta-analysis of 5 interventions found that L-citrulline supplementation had no statistically significant effect on either brachial or aortic systolic or diastolic blood pressure. Body weight status was identified as a source of heterogeneity. Earlier evidence did not support citrulline for blood pressure reduction in general populations.","abstract":"","citationCount":0},{"title":"l-Citrulline Supplementation: Impact on Cardiometabolic Health","year":2018,"journal":"Nutrients","doi":"10.3390/nu10070921","pmid":"30029482","url":"https://doi.org/10.3390/nu10070921","studyDesign":"systematic-review","fields":[],"conclusion":"Narrative review concludes that oral L-citrulline consistently increases plasma L-arginine and NO bioavailability more effectively than oral L-arginine supplementation (which is largely neutralised by first-pass metabolism). Evidence supports BP-lowering potential in pre-hypertensive and hypertensive populations, and preliminary metabolic and muscle health benefits in older adults.","abstract":"","citationCount":0},{"title":"Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction","year":2011,"journal":"Urology","doi":"10.1016/j.urology.2010.08.028","pmid":"21195829","url":"https://doi.org/10.1016/j.urology.2010.08.028","studyDesign":"rct","fields":[],"conclusion":"Single-blind RCT (24 men, 1.5 g/day L-citrulline vs placebo) found 50% of citrulline-treated men improved erection hardness scores vs 8.3% on placebo. Well-tolerated with no adverse events. While less potent than PDE5 inhibitors, L-citrulline represents a safe alternative for mild erectile dysfunction via the L-arginine/NO pathway.","abstract":"","citationCount":0}]},"machineReadable":{"markdownUrl":"https://nutripedia.co.uk/items/l-citrulline/markdown","jsonUrl":"https://nutripedia.co.uk/items/l-citrulline/json","llmsTxt":"https://nutripedia.co.uk/llms.txt"},"disclaimer":"Informational supplement research only. Not medical advice. Consult a qualified healthcare professional before taking supplements.","lastReviewed":"2026-04-01T00:00:00.000Z","updatedAt":"2026-04-20T00:00:00.000Z"}