L-Citrulline Malate
L-Citrulline Malate exerts its physiological effects through two primary, synergistic pathways: the nitric oxide synthesis pathway via L-citrulline and the Krebs cycle via malate.
L-Citrulline and the Arginine-Nitric Oxide Pathway
Upon oral ingestion, L-citrulline is readily absorbed in the small intestine, largely bypassing first-pass metabolism in the liver (the splanchnic extraction of citrulline is negligible). This is a key pharmacokinetic advantage over L-arginine supplementation, which is subject to significant degradation by the enzyme arginase in the gut and liver. After absorption, L-citrulline enters systemic circulation and is primarily taken up by the kidneys.
In the proximal tubule cells of the kidneys, L-citrulline is converted back into L-arginine in a two-step process that is part of the urea cycle.
1. Argininosuccinate Synthetase (ASS; EC 6.3.4.5): L-citrulline combines with aspartate in an ATP-dependent reaction to form argininosuccinate.
2. Argininosuccinate Lyase (ASL; EC 4.3.2.1): Argininosuccinate is then cleaved to form L-arginine and fumarate.
The newly synthesized L-arginine is released from the kidneys back into the bloodstream, effectively raising plasma L-arginine concentrations more efficiently and for a longer duration than direct L-arginine supplementation. This elevated systemic L-arginine becomes the rate-limiting substrate for the nitric oxide synthase (NOS) family of enzymes (eNOS, nNOS, iNOS).
Nitric Oxide Synthase (e.g., endothelial NOS or eNOS; EC 1.14.13.39) catalyzes the five-electron oxidation of a guanidino nitrogen of L-arginine, utilizing NADPH and molecular oxygen (O2) as co-substrates, to produce nitric oxide (NO) and L-citrulline (which can then be recycled). NO, a gaseous signaling molecule, diffuses to adjacent vascular smooth muscle cells and activates soluble guanylate cyclase (sGC). This enzyme converts guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP). Elevated cGMP levels activate protein kinase G (PKG), which in turn phosphorylates several downstream targets, leading to a decrease in intracellular calcium concentration and the relaxation of the smooth muscle (vasodilation). This vasodilation increases the lumen diameter of blood vessels, enhancing blood flow, oxygen, and nutrient delivery to tissues like skeletal muscle.
Pharmacokinetically, oral L-citrulline typically reaches peak plasma concentrations (Tmax) within 1-1.5 hours. The half-life is approximately 1.5-2 hours, but its effect on plasma arginine levels is more sustained.
Malate and the Tricarboxylic Acid (TCA) Cycle
Malate, the conjugate base of malic acid, is a key intermediate in the Krebs (Tricarboxylic Acid) cycle. Once absorbed, malate can enter the mitochondria and participate directly in cellular respiration. It is converted to oxaloacetate by malate dehydrogenase (EC 1.1.1.37), a reaction that reduces NAD+ to NADH. This NADH can then enter the electron transport chain to generate ATP. By providing an anaplerotic substrate for the TCA cycle, malate may help sustain aerobic energy production and potentially facilitate the clearance of lactate by promoting its conversion to pyruvate and subsequent entry into the TCA cycle. This proposed mechanism may contribute to reduced fatigue and improved endurance during exercise.
What is L-Citrulline Malate? +
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What is the best dose of L-Citrulline Malate for performance? +
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What's the difference between L-Citrulline and L-Citrulline Malate? +
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Everything About L-Citrulline Malate Article
The Definitive Guide to L-Citrulline Malate
L-Citrulline Malate is one of the most popular and effective ingredients in the sports nutrition world, prized for its ability to enhance blood flow, boost endurance, and deliver a satisfying muscle 'pump'. Whether you're a seasoned athlete or just starting your fitness journey, understanding how this powerful amino acid compound works can help you get the most out of your training. This guide breaks down the science, dosing, and practical applications of L-Citrulline Malate.
What It Does & What You Feel
The primary reason people take L-Citrulline Malate is for the 'pump'. This is the feeling of muscle fullness and vascularity that occurs during a workout. But what you feel is a direct result of what's happening inside your body:
Enhanced Blood Flow: Citrulline increases nitric oxide (NO) levels, which relaxes and widens your blood vessels. Increased Endurance: By improving oxygen and nutrient delivery to muscles and helping clear metabolic waste like ammonia, it can help you push out more reps and fight off fatigue. Reduced Soreness: Some research suggests that improved blood flow can aid in recovery and reduce delayed onset muscle soreness (DOMS).
When you take a proper dose (typically 6-8 grams) about an hour before training, you can expect to feel your muscles swell more during your working sets. The pump feels tighter, lasts longer, and you may find you can sustain your effort for a longer period before fatiguing.
The Science: From Amino Acid to Nitric Oxide
To understand L-Citrulline Malate, you need to know about the nitric oxide pathway. Here’s a simplified breakdown:
1. Ingestion & Absorption: You consume L-Citrulline Malate. Unlike its cousin L-Arginine, L-Citrulline is excellent at bypassing the liver and getting absorbed into your bloodstream. 2. Conversion in the Kidneys: Your kidneys efficiently convert L-Citrulline into L-Arginine, the direct fuel for nitric oxide production. 3. Nitric Oxide Production: An enzyme called nitric oxide synthase (NOS) uses this newly available L-Arginine to create nitric oxide (NO). 4. Vasodilation: NO signals the smooth muscles in your blood vessel walls to relax. This process, called vasodilation, widens the vessels, allowing more blood, oxygen, and nutrients to flow to your muscles.
The 'Malate' part of the name refers to malic acid, which is bonded to the citrulline. Malate is a key component in the Krebs cycle, your body's primary energy-producing process. The theory is that by providing extra malate, you can further support energy production and lactate clearance during intense exercise.
What The Research Says
The scientific community has studied citrulline extensively. The evidence is very clear on its core mechanism but more mixed on specific performance outcomes.
Strong Consensus: There is Grade A evidence that L-Citrulline supplementation is highly effective at increasing blood levels of L-Arginine. It is, paradoxically, better at this than taking L-Arginine itself. Moderate Evidence: There is Grade B evidence for its ability to improve blood pressure, particularly in populations with existing cardiovascular issues. Mixed/Emerging Evidence: For athletic performance, the results are less clear-cut. Some studies show small benefits for muscle recovery (Grade C), but a larger body of evidence shows no significant effect on aerobic or anaerobic exercise capacity (Grade D). Despite this, anecdotal evidence from millions of athletes remains overwhelmingly positive for its effects on the pump and fatigue resistance.
Dosing Guide
Dosing L-Citrulline Malate correctly is critical to experiencing its benefits. Many products on the market underdose this key ingredient.
Clinical Dose for Performance: 6,000 mg – 8,000 mg (6-8 grams) of L-Citrulline Malate. Dose for Circulatory Health: 2,000 mg of L-Citrulline (equivalent to ~3,500 mg of Citrulline Malate), taken three times per day. Red Flag: Any pre-workout or pump product with less than 3,000 mg of L-Citrulline Malate per serving is significantly underdosed for performance.
Forms Compared
You'll typically see two forms on the market:
L-Citrulline: The pure amino acid. Best for general health applications. A 3-5 gram dose is common. L-Citrulline Malate: The amino acid bonded to malic acid. This is the form used in most performance studies. It's important to know the ratio (usually 2:1 citrulline to malate). To get 4 grams of pure L-Citrulline from a 2:1 blend, you would need to take 6 grams of L-Citrulline Malate.
When & How To Take It
For optimal results, timing is key.
When: Take your full dose approximately 60 minutes before your workout. This gives your body enough time to absorb the citrulline, convert it to arginine, and ramp up nitric oxide production. How: Mix the powder with water or your pre-workout drink. It can be taken with or without food, but taking it on a relatively empty stomach may speed absorption.
Stacking L-Citrulline Malate
Citrulline Malate works well with other ingredients to maximize performance:
Beta-Alanine: For muscular endurance and buffering lactic acid. Creatine Monohydrate: For strength, power, and cell hydration. Betaine Anhydrous: For power output and cellular hydration. Nitrates (from Beet Root): To open up a second, complementary pathway for nitric oxide production.
Who Should Take It
Resistance Trainers: Anyone lifting weights who wants to improve their muscle pump, endurance, and recovery. Athletes: Individuals in sports requiring sustained effort and good blood flow. Individuals Focused on Cardiovascular Health: Those looking to support healthy blood pressure and circulation (under a doctor's guidance).
Who Should NOT Take It
People on Blood Pressure Medication: If you take nitrates, PDE5 inhibitors (like Viagra), or other antihypertensive drugs, you must consult your doctor. The combined effect could cause a dangerous drop in blood pressure. Pregnant or Nursing Women: There is insufficient safety data for these populations.
The Bottom Line
L-Citrulline Malate is a research-backed, effective supplement for enhancing blood flow and achieving a powerful muscle pump. While the direct evidence for massive strength or speed gains is still developing, its role in improving workout quality, reducing fatigue, and supporting recovery is well-established both anecdotally and in its proven biological mechanism. For best results, ensure you are taking a clinical dose of 6-8 grams of L-Citrulline Malate about an hour before you train.
* These statements have not been evaluated by the Food and Drug Administration. This information is for educational purposes only and is not intended to diagnose, treat, cure, or prevent any disease. Consult a healthcare provider before beginning any supplement regimen.