Citrulline
Summary
An amino acid that raises nitric oxide bioavailability more effectively than arginine itself. Meta-analyses show small, marginal benefits for high-intensity performance, reps to failure, and post-exercise soreness.
Mechanism
Oral citrulline is converted to arginine, primarily in the kidneys, raising plasma arginine and nitric oxide bioavailability — more effectively than oral arginine itself. Nitric oxide drives vasodilation and increased skeletal-muscle blood flow.
Reported effects
Ratings are relative to peers in the same category, not absolute claims.
Studied dosing — research context
Performance trials most commonly use 6-8 g of citrulline malate taken acutely 1-2 hours before exercise (8 g is the most common dose; at a 2:1 ratio that is about 5.3 g of L-citrulline). Chronic L-citrulline trials typically use 3-6 g/day. These are doses used in research, not guidance.
Research context only. This is not a recommendation.
Safety
Generally well tolerated in trials. Stomach discomfort was reported in roughly 15% of subjects in the landmark Pérez-Guisado trial.
Limitations
Individual trials show mixed results with small samples (roughly 12-40 subjects); benefits are marginal rather than transformative. Most performance studies use citrulline malate, so the independent contribution of malate versus citrulline itself is unresolved.
References
- Trexler et al., Sports Med (2019) — meta-analysis of citrulline and high-intensity strength/power performance
- Pérez-Guisado & Jakeman, J Strength Cond Res (2010) — citrulline malate, anaerobic performance, and soreness
- Rhim et al., J Sport Health Sci (2020) — meta-analysis of citrulline, soreness, and perceived exertion