Citrulline Malate: The Blood Flow Amino Acid With Real Performance Data

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L-citrulline is a non-essential amino acid that the body converts to L-arginine, the precursor to nitric oxide. Taking citrulline raises blood arginine and downstream NO signalling more reliably than taking arginine directly, because oral arginine is largely cleared by first-pass hepatic and intestinal metabolism. Citrulline malate adds malate (a Krebs-cycle intermediate) to the amino acid in a 2:1 or 1:1 ratio.

Performance evidence

A meta-analysis of 12 acute-dose randomised crossover trials examined citrulline supplementation (with or without malate) on high-intensity strength and power performance. Pooled across studies (single-dose or short-term), citrulline produced a small but statistically significant improvement in performance (effect size ~0.20), with the largest effects in resistance-exercise volume and lower effects on single-effort maximal strength (Trexler 2019; PMID 30895562; DOI 10.1007/s40279-019-01088-8). The 6–8 g pre-workout dose used in many trials reduces fatigue in later sets more reliably than it boosts a single 1-rep maximum.

Blood pressure and vascular

A review of cardiometabolic trials of L-citrulline reported modest reductions in resting and exercise systolic blood pressure (typically 2–5 mmHg), improvements in flow-mediated dilation, and limited but plausible effects on arterial stiffness in adults with hypertension or pre-hypertension; effects are larger and more consistent with chronic dosing (3–6 g/day for 8+ weeks) than with single doses (Allerton 2018; PMID 30029482; DOI 10.3390/nu10070921).

Erectile function

A small single-blind RCT in 24 men with mild erectile dysfunction tested L-citrulline 1.5 g/day for one month versus placebo. Erection hardness score improved from 3 to 4 in 12 of 24 participants on citrulline vs 2 of 24 on placebo, with no adverse events (Cormio 2011; PMID 21195829; DOI 10.1016/j.urology.2010.08.028). The effect is smaller than that of PDE5 inhibitors, but the safety profile is excellent.

Dose and timing

Performance: 6–8 g citrulline malate (roughly 4–5 g pure L-citrulline) about 30–60 minutes pre-workout. Vascular and ED applications: 3–6 g pure L-citrulline daily, often split. Pure L-citrulline is cheaper per effective dose than citrulline malate but lacks the small malate contribution.

Safety

Very well tolerated; no established UL for supplemental citrulline. Mild GI symptoms at >10 g/day. Use caution stacking with PDE5 inhibitors (additive hypotension) or antihypertensives. Pregnancy data are limited.