Supplements: Citrulline Malate
6g citrulline malate (2:1) produced a 52.92% increase in reps to fatigue and 40% reduction in DOMS vs placebo (Pérez-Guisado & Jakeman 2010, PMID 20386132). Most pre-workouts contain 2–3g — half the effective dose.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Evidence Tier | 2 | tier | Tier 2 — Moderate: meaningful human RCT data, but some mixed results across populations and protocols |
| Effective Dose | 6–8 | g citrulline malate | 2:1 ratio provides 4–5g citrulline; take 30–60 min pre-workout |
| Rep Increase (bench press) | 52.92 | % | vs placebo in Pérez-Guisado & Jakeman 2010 using 8g citrulline malate |
| DOMS Reduction | 40 | % | 24–48h post-exercise soreness reduction at 8g citrulline malate dose |
| Blood Pressure Reduction | 4–6 | mmHg | Resting systolic blood pressure at chronic doses; separate from acute performance benefit |
| Typical Pre-Workout Dose | 2–3 | g | Common underdosing — half or less of the studied effective dose |
Citrulline malate has become one of the most researched pre-workout ingredients, though it remains chronically underdosed in commercial products. Understanding its mechanism explains both why it works and why the dose on most labels is inadequate.
The Arginine Problem
The intuitive route to raising nitric oxide would be to take oral arginine — arginine is the direct NO precursor. The problem is first-pass hepatic metabolism: the liver contains high concentrations of arginase and rapidly catabolizes oral arginine before it reaches systemic circulation. Clinical studies on oral arginine show disappointing results for NO-mediated performance effects precisely because so little survives absorption.
Citrulline solves this problem. It is absorbed in the small intestine and converted to arginine in the kidneys — bypassing hepatic first-pass destruction. Schwedhelm et al. 2008 (PMID 17662090) demonstrated that oral citrulline raises plasma arginine levels significantly higher and more durably than equimolar oral arginine.
Performance Evidence
| Dose (Citrulline Malate) | Effect on Reps/Performance | Blood Flow Effect | Study PMID | Evidence Tier |
|---|---|---|---|---|
| 8g (2:1) | +52.92% reps to fatigue (bench press) | Improved limb perfusion | 20386132 | Tier 2 |
| 8g (2:1) | Reduced DOMS 40% at 24h | Improved waste clearance | 20386132 | Tier 2 |
| 6g (2:1) | Improved cycling time trial performance | Reduced O2 cost | 20499249 | Tier 2 |
| 2–3g (typical pre-workout) | Minimal/unclear | Marginal | N/A | Insufficient |
| 6g L-citrulline (pure) | Equivalent to ~8g CM | Similar vasodilation | 17662090 | Tier 2 |
The Underdosing Problem
Checking the labels of popular pre-workout products consistently reveals 2–3g of citrulline malate — roughly 40–50% of the minimum effective dose studied in RCTs. Proprietary blends often obscure the actual dose. If your pre-workout does not clearly state at least 6g of citrulline malate (or 4g of L-citrulline), consider supplementing separately.
Blood Pressure Effect
Citrulline’s NO-raising mechanism also reduces resting blood pressure by 4–6 mmHg systolic in studies using chronic dosing. This is a genuine cardiovascular benefit but is a secondary effect from a training perspective. Athletes with already-low blood pressure should note this and monitor response.
Dosing Protocol
- Citrulline malate (2:1): 6–8g, 30–60 minutes pre-workout
- Pure L-citrulline: 4–6g, same timing
- Do not use on an empty stomach if GI sensitive — mix with a small amount of food
- Daily use is fine; no loading protocol required; acute dosing is sufficient
Related Pages
Sources
- Pérez-Guisado J, Jakeman PM. Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. J Strength Cond Res. 2010;24(5):1215-1222.
- Sureda A et al. L-citrulline-malate influence over branched chain amino acid utilization during exercise. Eur J Appl Physiol. 2010;110(2):341-351.
- Schwedhelm E et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine. Br J Clin Pharmacol. 2008;65(1):51-59.
Frequently Asked Questions
What does citrulline malate actually do?
Citrulline converts to arginine in the kidneys, bypassing the liver which would break down oral arginine before it reaches circulation. Arginine is a precursor to nitric oxide (NO), which dilates blood vessels. This improves blood flow, oxygen delivery, and waste removal during exercise. The malate component also supports the TCA cycle for energy production.
How much citrulline malate should I take?
The studied effective dose is 6–8g of citrulline malate (2:1 ratio), which provides 4–5g of citrulline. Take it 30–60 minutes before training. Most commercial pre-workouts contain only 2–3g, which is underdosed — check your label and supplement separately if needed.
Is citrulline better than arginine for pumps and blood flow?
Yes. Oral arginine is extensively broken down during first-pass hepatic metabolism, so very little reaches systemic circulation. Citrulline bypasses the liver, converts to arginine in the kidneys, and actually raises plasma arginine levels higher and more sustainably than an equivalent oral arginine dose (PMID 17662090). Arginine supplements for performance purposes are largely obsolete.
Does citrulline malate actually increase muscle endurance or is it just a pump product?
Both. The blood flow enhancement is real and produces the training pump effect. But Pérez-Guisado & Jakeman 2010 demonstrated genuine muscular endurance improvements — 52.92% more reps to fatigue in bench press — not just subjective pump sensation. The performance benefit is validated in resistance training contexts.
Can I take just L-citrulline instead of citrulline malate?
Yes. Pure L-citrulline at 4–6g provides equivalent citrulline content to 6–8g of citrulline malate (2:1). The malate component may add modest TCA cycle support and is theoretically beneficial, but most studies showing performance effects used the malate form, so the evidence base is slightly stronger for citrulline malate.