Question explored with the scientific record
Are there any studies that show l-citrulline lowers blood pressure?
The evidence for L-citrulline lowering blood pressure is mixed and limited to specific, short-term stress conditions in small studies.
The best human trial on this question is a 2016 randomized crossover study of 16 overweight men. It found that 6 grams of L-citrulline per day for 14 days did not lower resting blood pressure at all [2]. The only reductions were seen during physical stress (handgrip exercise) combined with cold exposure, where it blunted the expected rise in blood pressure [2]. That is a very different claim from "lowers blood pressure" in daily life.
A 2025 narrative review confirms the inconsistency. It reports that L-citrulline supplementation produced a statistically significant reduction in systolic blood pressure in one cited study, but the diastolic reduction of 4.1 mmHg did not reach statistical significance [1]. The review's overall conclusion is that the evidence is inconsistent and long-term trials are needed [1].
The mechanism is plausible: L-citrulline boosts nitric oxide, which relaxes blood vessels [1]. But a plausible mechanism is not proof of clinical effect. The only direct human trial on resting blood pressure found no effect [2]. The watermelon juice study (providing 780 mg L-citrulline) found it prevented a post-exercise blood pressure rise only in women, but did not test resting values [3].
| Condition | Effect of L-citrulline | Source |
|---|---|---|
| Resting blood pressure (overweight men) | No significant effect | [2] |
| Blood pressure during exercise + cold stress | Blunted rise (aortic SBP, DBP, MAP) | [2] |
| Systolic BP in a cited study | Statistically significant reduction | [1] |
| Diastolic BP in the same cited study | 4.1 mmHg reduction, not significant | [1] |
My call: L-citrulline does not reliably lower resting blood pressure based on the best available human trial. Claims of benefit are drawn from short-term stress tests or inconsistent studies. Confidence: low for a meaningful resting blood pressure effect in the general population.
Sources used 3
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L-Citrulline and L-Arginine Supplementation in Cardiovascular and Exercise Physiology - A Comprehensive Review on Endothelial Function, Blood Pressure, and Physical Performance
A narrative review concludes that L-arginine and L-citrulline supplementation may improve cardiovascular function and exercise capacity, particularly in at-risk populations, through enhanced nitric oxide bioavailability, but evidence is inconsistent and long-term RCTs are needed.
DOI: 10.12775/qs.2025.45.66468 -
l -Citrulline supplementation attenuates blood pressure, wave reflection and arterial stiffness responses to metaboreflex and cold stress in overweight men
In a randomised crossover trial, 14 d of 6 g/d L-citrulline attenuated aortic blood pressure, wave reflection and brachial-ankle pulse wave velocity responses to metaboreflex activation plus cold stress, but not resting values, in overweight/obese men.
DOI: 10.1017/s0007114516001811 -
Effect of acute watermelon juice supplementation on post-submaximal exercise heart rate recovery, blood lactate, blood pressure, blood glucose and muscle soreness in healthy non-athletic men and women
A randomized crossover study in healthy, non-athletic adults tested whether a single pre-exercise dose of watermelon juice (355 mL providing 780 mg L-citrulline) alters post-submaximal exercise heart rate recovery, blood lactate, blood pressure, blood glucose, and muscle sorenes…
DOI: 10.1080/09637486.2019.1675604