Across 5 studies, 4 reported beneficial effects of L-citrulline on reducing aortic systolic blood pressure, with effect sizes ranging from moderate to large. The median study duration was 28 days, and the most-studied dose was 6 g/day, with effects observed in clinical populations including hypertensive postmenopausal women and older adults with type 2 diabetes.
Caveats: Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed). The meta-analysis included in this set reported no significant change, highlighting potential inconsistency. All studies were small (n ≤ 22), limiting generalizability.
reduced aortic systolic BP (Δ3 ± 5 vs. Δ-4 ± 6 mmHg) at rest
aortic SBP (Δ-10 ± 14 vs. Δ4 ± 12 mmHg; P = 0.005) ... responses to the CPT were significantly attenuated following L-CIT supplementation vs. placebo.
Four weeks of L-citrulline supplementation improved... aortic systolic blood pressure... in the fasted state compared to placebo (all p < 0.05). During acute hyperglycemia, CIT supplementation... reduced aortic systolic BP... compared to placebo (all p < 0.05).
Also, there was no changes in aortic systolic (change 0.22 mmHg; 95% CI -4.81, 4.38 mmHg) ... blood pressure after L-citrulline supplementation.
CIT attenuated ΔSBP (−9 ± 2 v. −1 ± 1 mmHg, P = 0·006)