{"url":"https://whatshealthyandwhy.com/l-citrulline/nitric-oxide-blood-pressure-and-exercise","path":"/l-citrulline/nitric-oxide-blood-pressure-and-exercise","alternates":{"json":"https://whatshealthyandwhy.com/api/articles/l-citrulline/nitric-oxide-blood-pressure-and-exercise.json","markdown":"https://whatshealthyandwhy.com/l-citrulline/nitric-oxide-blood-pressure-and-exercise.md"},"topic":{"slug":"l-citrulline","name":"L-Citrulline","url":"https://whatshealthyandwhy.com/l-citrulline"},"slug":"nitric-oxide-blood-pressure-and-exercise","order":1,"title":"Nitric Oxide, Blood Pressure, and Exercise Performance","question":"Does L-citrulline lower blood pressure and boost exercise performance?","answer":"L-citrulline likely lowers systolic blood pressure by about 4 mmHg in people with high blood pressure and modestly improves exercise performance.","description":"How L-citrulline boosts nitric oxide production, supports cardiovascular health, and improves exercise performance through the arginine-nitric oxide pathway","confidence":3,"confidenceNote":"Meta-analyses of 8 blood pressure trials (12–34 people each), 8 strength trials (137 people) and 13 recovery trials (206 people); effects are small.","evidenceSummary":{"rctCount":4,"observationalCount":0,"metaAnalysisCount":3,"totalParticipants":"350+","replicated":true,"newestStudyYear":2022},"category":{"categoryTitle":"What's Good For You","categorySlug":"good-for-you","subcategoryName":"Supplements & Vitamins","subcategorySlug":"supplements","url":"https://whatshealthyandwhy.com/explore/good-for-you/supplements"},"actions":["Eat watermelon, including some white rind, which has more citrulline than the flesh; 500 g gives only 1–1.5 g, far less than trial doses.","For blood pressure, trials used 3–9 g a day, with a diastolic drop only at 6 g or more [1].","For exercise, take 6–8 g of citrulline malate (or 4–6 g L-citrulline) 40–60 minutes before training; the key trial used 8 g [3]."],"cautions":["People taking blood pressure medicines or PDE5 inhibitors such as sildenafil should use caution, since blood pressure lowering can add up.","Mild stomach upset is occasionally reported at 8 g or more a day; no serious adverse events were reported in trials.","Trials were small and short, so effects on heart attacks or strokes are unknown, and normal blood pressure did not fall [1][7]."],"simpleText":"L-citrulline is a non-essential amino acid found naturally in watermelon, cucumber, and pumpkin. Unlike most amino acids, it is not used to build proteins — instead, it travels to the kidneys where it is converted into L-arginine, which then drives the production of nitric oxide [6][7]. Nitric oxide relaxes the walls of blood vessels, widening them and improving blood flow throughout the body. The practical result is lower blood pressure [1], better oxygen delivery to muscles during exercise, and reduced soreness in the hours after training [3]. It is one of the few supplements with solid clinical evidence across both cardiovascular health and athletic performance.","mediumText":"The Arginine-Nitric Oxide Pathway\n\nMost people who want to raise nitric oxide try taking L-arginine directly — but this approach is limited by poor oral bioavailability. Arginase enzymes in the gut and liver break most of it down before it reaches circulation. L-citrulline sidesteps this problem entirely: it is absorbed intact through the small intestine, transported to the kidneys, and converted to arginine there. Reviews of the evidence conclude that citrulline supplementation raises arginine levels and nitric oxide synthesis more effectively than arginine supplementation itself [6].\n\nThe resulting arginine fuels endothelial nitric oxide synthase (eNOS), the enzyme that produces nitric oxide in blood vessel walls. NO then diffuses into surrounding smooth muscle, triggering relaxation and vasodilation. This is the same pathway activated by exercise, sunlight, and dietary nitrates from beets and leafy greens — citrulline simply provides more substrate to keep it running. See our beets page for a complementary dietary route to NO support.\n\nErection is also a nitric oxide–mediated vascular event, so the same pathway matters for erectile function, but the evidence for citrulline's effect there is still preliminary.\n\nBlood Pressure and Vascular Health\n\nA 2019 systematic review and meta-analysis pooling 8 randomized controlled trials found that L-citrulline supplementation lowered systolic blood pressure by about 4 mmHg on average, and that diastolic pressure fell significantly only in the trials that used 6 g/day or more [1]. The effect is most evident in people with prehypertension or hypertension, and not in people whose blood pressure is already normal [7].\n\nA 2022 randomized trial in hypertensive postmenopausal women tested 10 g/day of L-citrulline for 4 weeks [2]. The researchers used brachial artery flow-mediated dilation — a validated imaging measure of endothelial function — alongside blood pressure monitoring. L-citrulline increased both plasma arginine and flow-mediated dilation, and reduced aortic diastolic blood pressure and mean arterial pressure compared to placebo. The findings are particularly relevant for women after menopause, when the loss of estrogen impairs eNOS activity and accelerates vascular aging.\n\nMetabolic Health and Type 2 Diabetes\n\nCitrulline also shows early promise for people with metabolic conditions [6]. In patients with type 2 diabetes, one month of 2,000 mg/day produced a 38% increase in plasma nitric oxide and a 21% reduction in arginase activity [9]. Arginase is an enzyme that competes with nitric oxide synthase for the same arginine, so when it is overactive — as it often is in diabetes — less arginine is available for NO production and blood vessel function suffers [9]. By reducing arginase activity, citrulline may help shift the balance back toward NO production and healthier vascular tone.\n\nExercise Performance\n\nMuch of the exercise research uses citrulline malate — L-citrulline bound to malic acid in a 2:1 ratio. The malate component may contribute independently by supporting the citric acid cycle, potentially improving energy production during sustained high-intensity effort.\n\nThe most-cited trial in this area tested 8 g of citrulline malate taken before a bench press protocol in 41 men [3]. Compared to placebo in a double-blind crossover design, citrulline malate increased the number of repetitions completed across 16 sets by more than 50%. Post-exercise muscle soreness was reduced by 40% at both 24 and 48 hours. Later meta-analyses confirmed a consistent, if more modest, ergogenic effect across different training contexts.\n\nA 2020 meta-analysis of 13 trials found that citrulline supplementation reduced perceived effort during exercise (p = 0.03) and muscle soreness at 24 hours post-exercise (p = 0.04) [4]. Blood lactate levels were not significantly affected, suggesting the anti-fatigue effect works through mechanisms beyond simple lactate clearance — possibly including enhanced blood flow to working muscles and faster removal of metabolic waste.\n\nHead to head, a 7-day crossover trial in 10 healthy men found that 6 g/day of L-citrulline improved oxygen-uptake kinetics and tolerance of severe-intensity cycling, while the same dose of L-arginine did not [8].\n\nPractical Dosage\n\nFor blood pressure support: 3–6 g L-citrulline per day, ideally taken consistently for at least 4–6 weeks.\n\nFor exercise performance: 6–8 g citrulline malate (2:1 form), or 4–6 g pure L-citrulline, taken 40–60 minutes before training.\n\nFood sources: Watermelon is the richest dietary source — roughly 2–3 g of citrulline per kilogram of flesh, or about 1 g per two cups — and the white rind contains more citrulline than the red flesh. Cucumber, pumpkin, squash, and bitter melon also contain meaningful amounts, though supplemental doses far exceed what food provides: about 500 g of watermelon a day supplies only 1–1.5 g, compared with the 3–6 g a day used for blood pressure support.\n\nL-citrulline is well tolerated with a low side effect profile. Mild gastrointestinal discomfort is occasionally reported at high doses (8+ g), and doses of up to 10 g/day have been used in short-term trials [2]. No serious adverse events have been reported in human trials to date. People taking blood pressure medications or PDE5 inhibitors (e.g., sildenafil) should use caution, since the blood-pressure-lowering effects could add up.","deepText":"Evidence Review\n\nOverview\n\nAllerton et al. (2018) reviewed the case for L-citrulline in cardiometabolic health [6]. They note that oral arginine is largely ineffective at raising nitric oxide for a variety of reasons, whereas citrulline is not quantitatively extracted by the gut or liver and so is more effective at raising arginine levels and nitric oxide synthesis. They describe its blood-pressure-lowering effect as promising in adults with prehypertension or hypertension, with animal evidence for protection of the blood vessel lining, and the evidence for benefits to muscle and metabolic health, mainly in older or susceptible people, as preliminary. The review closes by identifying where further research is needed.\n\nBlood Pressure and Endothelial Function\n\nBarkhidarian et al. (2019) conducted a systematic review and meta-analysis of randomized controlled trials of L-citrulline and blood pressure; 8 trials, yielding 10 data sets, met the inclusion criteria [1]. Sample sizes ranged from 12 to 34 participants, mean ages from 22 to 71 years, doses from 3 to 9 g/day, and durations from 1 to 17 weeks. Pooled across trials, supplementation lowered systolic blood pressure by 4.10 mmHg (95% CI −7.94 to −0.26; p = 0.037). The overall change in diastolic pressure (−2.08 mmHg; 95% CI −4.32 to 0.16; p = 0.069) did not reach significance, but a subgroup analysis found a significant diastolic reduction in the trials that used 6 g/day or more (−2.75 mmHg; 95% CI −5.37 to −0.12; p = 0.04). Sample sizes this small are reasonable for mechanistic vascular studies but not large enough to draw conclusions about hard clinical endpoints like cardiovascular events. A reduction of about 4 mmHg is modest for an individual but meaningful at the population level, where reductions of that size are associated with lower rates of stroke and coronary heart disease.\n\nMaharaj et al. (2022) conducted a well-controlled crossover trial in 25 hypertensive postmenopausal women, testing 10 g/day L-citrulline versus placebo over 4 weeks per condition [2]. The crossover design is valuable here because each participant serves as their own control, reducing confounding from the substantial individual variation in vascular function. Key outcomes included plasma L-arginine (confirming the citrulline-to-arginine conversion pathway was working as expected), brachial artery flow-mediated dilation measured by ultrasound (confirming improved endothelial function), and automated blood pressure measurement. Aortic diastolic BP and mean arterial pressure were significantly reduced with L-citrulline versus placebo. The authors attributed the effects to increased L-arginine availability driving eNOS activity. This trial is notable for using both mechanistic biomarkers and clinical outcomes simultaneously.\n\nFigueroa et al. (2017) reviewed L-citrulline and watermelon together, treating both as sources of the same arginine–nitric oxide pathway [7]. Acute intake clearly raises plasma arginine, but the short-term gain in nitric oxide production and vasodilation is inconsistent, which the authors suggest is why a single dose of citrulline or watermelon has not reliably improved exercise tolerance. Chronic supplementation, by contrast, increased nitric oxide synthesis, lowered blood pressure, and may increase peripheral blood flow, changes that paralleled better skeletal muscle oxygenation and endurance performance. The blood-pressure-lowering effect was evident in adults with prehypertension or hypertension but not in people with normal blood pressure, although citrulline may blunt the blood pressure response to exercise in normotensive men.\n\nExercise Performance\n\nPérez-Guisado and Jakeman (2010) established the foundational evidence for citrulline malate in resistance training [3]. Their randomized, double-blind crossover study had 41 men complete two separate pectoral training sessions — one with 8 g citrulline malate and one with placebo, separated by a washout period. The increase in repetitions to failure exceeded 50% on citrulline malate versus placebo. The 40% reduction in muscle soreness at 24 and 48 hours post-exercise was equally striking. While these effect sizes are larger than what later meta-analyses found on average, the study was important for establishing the plausibility and direction of citrulline's ergogenic effect in a real training protocol.\n\nVårvik, Bjørnsen, and Gonzalez (2021) pooled data from 8 double-blind, placebo-controlled trials (137 participants, including 101 trained men, 26 women, and 9 untrained men) in a formal meta-analysis focused on repetition performance during strength training [5]. They found a statistically significant ergogenic effect of citrulline malate (Hedges's g = 0.20): 6–8 g taken 40–60 minutes before exercise increased repetitions by 3 ± 5 (6.4 ± 7.9%) compared with placebo (p = .022), a small advantage. The lower-body subanalysis showed a tendency toward an effect (SMD 0.27, p = .051), while the upper-body effect was not significant (SMD 0.16, p = .131). The authors concluded that acute citrulline malate supplementation may delay fatigue and enhance muscle endurance during high-intensity strength training.\n\nRhim et al. (2020) analyzed the recovery side of the equation, pooling 13 trials totaling 206 participants [4]. Their meta-analysis found significant reductions in perceived exertion (standardized mean difference, p = 0.03) and muscle soreness at 24 hours (p = 0.04). The 48-hour soreness result trended toward significance. Blood lactate at multiple post-exercise time points did not show significant reductions, which argues against the simple hypothesis that citrulline works by clearing lactate. The authors suggest enhanced blood flow, improved oxygen delivery, and potentially malate's role in the citric acid cycle as more likely contributors. …","deepTruncated":true,"references":[{"id":"1","title":"Effects of L-citrulline supplementation on blood pressure: A systematic review and meta-analysis","authors":"Barkhidarian B, Khorshidi M, Shab-Bidar S, Hashemi B","year":2019,"journal":"Avicenna Journal of Phytomedicine","pmid":"30788274","url":"https://pubmed.ncbi.nlm.nih.gov/30788274/"},{"id":"2","title":"Effects of L-Citrulline Supplementation on Endothelial Function and Blood Pressure in Hypertensive Postmenopausal Women","authors":"Maharaj A, Fischer SM, Dillon KN, Kang Y, Martinez MA, Figueroa A","year":2022,"journal":"Nutrients","pmid":"36297080","url":"https://pubmed.ncbi.nlm.nih.gov/36297080/"},{"id":"3","title":"Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness","authors":"Pérez-Guisado J, Jakeman PM","year":2010,"journal":"Journal of Strength and Conditioning Research","pmid":"20386132","url":"https://pubmed.ncbi.nlm.nih.gov/20386132/"},{"id":"4","title":"Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: A systematic review and meta-analysis","authors":"Rhim HC, Kim SJ, Park J, Jang KM","year":2020,"journal":"Journal of Sport and Health Science","pmid":"33308806","url":"https://pubmed.ncbi.nlm.nih.gov/33308806/"},{"id":"5","title":"Acute Effect of Citrulline Malate on Repetition Performance During Strength Training: A Systematic Review and Meta-Analysis","authors":"Vårvik FT, Bjørnsen T, Gonzalez AM","year":2021,"journal":"International Journal of Sport Nutrition and Exercise Metabolism","pmid":"34010809","url":"https://pubmed.ncbi.nlm.nih.gov/34010809/"},{"id":"6","title":"l-Citrulline Supplementation: Impact on Cardiometabolic Health","authors":"Allerton TD, Proctor DN, Stephens JM, Dugas TR, Spielmann G, Irving BA","year":2018,"journal":"Nutrients","pmid":"30029482","url":"https://pubmed.ncbi.nlm.nih.gov/30029482/"},{"id":"7","title":"Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance","authors":"Figueroa A, Wong A, Jaime SJ, Gonzales JU","year":2017,"journal":"Current Opinion in Clinical Nutrition and Metabolic Care","pmid":"27749691","url":"https://pubmed.ncbi.nlm.nih.gov/27749691/"},{"id":"8","title":"l-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans","authors":"Bailey SJ, Blackwell JR, Lord T, Vanhatalo A, Winyard PG, Jones AM","year":2015,"journal":"Journal of Applied Physiology","pmid":"26023227","url":"https://pubmed.ncbi.nlm.nih.gov/26023227/"},{"id":"9","title":"L-Citrulline Supplementation Increases Plasma Nitric Oxide Levels and Reduces Arginase Activity in Patients With Type 2 Diabetes","authors":"Shatanawi A, Momani MS, Al-Aqtash R, Hamdan MH, Gharaibeh MN","year":2020,"journal":"Frontiers in Pharmacology","pmid":"33414716","url":"https://pubmed.ncbi.nlm.nih.gov/33414716/"}],"wordCount":2139,"source":{"path":"src/content/topics/l-citrulline/nitric-oxide-blood-pressure-and-exercise.md"},"citeAs":"“Does L-citrulline lower blood pressure and boost exercise performance?.” What's Healthy and Why. https://whatshealthyandwhy.com/l-citrulline/nitric-oxide-blood-pressure-and-exercise","notice":"General information backed by peer-reviewed research, not medical advice."}