L-Citrulline has become one of the most popular supplements in fitness, performance, and health circles — and for good reason. Backed by a growing body of research, L-Citrulline and its more common athletic form citrulline malate offer benefits ranging from enhanced physical performance and endurance to improved blood flow and nitric oxide production, which may even support certain mental tasks and health conditions.

🧬 What Is L-Citrulline & How It Works

L-Citrulline is a non-essential amino acid that your body produces naturally and that is also found in foods like watermelon. Once ingested, it’s converted into L-arginine, which is a precursor in the production of nitric oxide (NO) — a potent molecule that relaxes blood vessels and improves blood flow. Better blood flow can enhance nutrient and oxygen delivery to muscles and organs. Cleveland Clinic

🩺 Mechanisms That Drive Its Benefits

➡ Nitric Oxide Boost: By increasing arginine availability more efficiently than arginine supplements themselves, citrulline raises nitric oxide levels, improving vascular function.
➡ Ammonia & Lactate Clearance: Citrulline is part of the urea cycle, helping clear ammonia — a fatigue-linked byproduct of intense exercise — possibly delaying fatigue and improving energy production.
➡ ATP Support (Citrulline Malate): In citrulline malate, the malate part may support cellular energy via the Krebs cycle, which might further assist endurance and recovery.

💪 Physical Performance Benefits (Strength, Endurance & Recovery)

1. Strength & Muscular Endurance

• Acute citrulline malate supplementation (6–8 g taken 40–60 minutes pre-workout) increases total repetitions performed during high-intensity resistance training compared with placebo.

• Six-week trials show that both L-citrulline and citrulline malate can improve upper-body muscular endurance compared to placebo.

2. Reduced Rate of Perceived Exertion & Muscle Soreness

A meta-analysis found that citrulline supplementation significantly reduced perceived exertion (how hard workouts feel) and muscle soreness after exercise.

3. Cycling & Fatigue Resistance

In trained cyclists, L-citrulline improved subjective feelings of fatigue and concentration during time trials — likely linked to enhanced blood flow and metabolic waste clearance. Journal of the International Society of Sports Nutrition 

Best for:

• Strength training

• HIIT and functional fitness (CrossFit)

• Sprint or anaerobic power activities

• Repeated sets and high-volume workouts

🧠 Cognitive & “Mental Performance” Potential

While most research focuses on physical performance, enhanced nitric oxide and blood flow may also support brain perfusion and metabolic efficiency — theoretically benefiting tasks like focus and sustained attention. Not only that, but there are some studies that suggest L-citrulline may benefit patients who have undergone some cerebral ischemic insult and even prevent some injuries to begin with. PubMed

The blood-brain barrier (BBB) protects brain tissue from toxins and excessive glutamate, which can cause excitotoxicity (overactivation leading to cell damage). In a cellular model:

• L-citrulline increased endothelial nitric oxide synthase (eNOS) expression

• Decreased damaging inducible nitric oxide synthase (iNOS) expression

• Improved cell viability under glutamate-induced stress

These findings suggest citrulline may help protect BBB health and neural cells from excitotoxic injury, which is a mechanism relevant to neurodegeneration and brain insults. National Library of Medicine

❤️ Other Health & Therapeutic Benefits

Heart Health & Blood Pressure

Some studies suggest L-citrulline may help lower systolic and diastolic blood pressure, possibly benefiting cardiovascular health — though results are mixed and more research is needed. Forbes

Erectile Function

Because nitric oxide supports vascular dilation, some small trials report improvements in erectile dysfunction symptoms, a clinical benefit stemming from the same mechanism that helps circulation.

Special Populations

• Older adults, people with hypertension, or individuals with mild vascular dysfunction may see benefits — though consulting a clinician is recommended due to individual health factors.

🧪 Different Forms: L-Citrulline vs Citrulline Malate

L-Citrulline (Pure)

• Focuses on nitric oxide production and vascular function

• Best for muscle “pump”, blood flow, and circulatory support

• Typically dosed 3–6 g/day

Citrulline Malate

• Combines L-citrulline with malic acid, which plays a role in energy metabolism

• May provide additional support for fatigue resistance and energy production during intense training

• Often dosed 6–8 g 30–60 minutes pre-workout

Prosupps

✅ Which to choose?

• If your goal is better pumps and blood flow, pure L-citrulline may be ideal. An example of this would be weight lifting.

• If you want endurance and fatigue reduction during workouts, citrulline malate is often preferred.

• Many supplements may blend the two forms together so that you get the best of both worlds.

📈 Dosage & Timing

Recommended Dosages

• L-Citrulline: 3–6 g per day for vascular support or general nitric oxide benefits.

• Citrulline Malate: 6–8 g taken ~30–60 min pre-exercise for performance effects.

When to Take It

For exercise performance, take 30–60 minutes before workouts to align with peak nitric oxide levels. For general cardiovascular benefits, dosing can be split or taken at any time of day.

⚠️ Side Effects & Safety

L-citrulline is generally well-tolerated, even at doses up to 10 g/day in most studies.
Possible mild side effects include:

• Stomach discomfort or heartburn

• Occasional gas or bloating (rare)

Precautions:

• Individuals with low blood pressure or on antihypertensive medications should consult a clinician — citrulline’s vasodilatory effects may interact with medications.

• Limited research in pregnancy/breastfeeding and children — consult a provider before use.

🔗 Supplements That Can Augment Citrulline’s Benefits

To enhance the effects of citrulline or address related performance pathways:

• Beta-alanine: May help buffer acid build-up and delay fatigue.

• Creatine: Supports ATP regeneration and strength gains.

• Beetroot juice or dietary nitrates: Also increase nitric oxide via a different pathway.
  (Dosing and timing for combined strategies should be tailored with professional guidance.)

Note: As with all supplements, speak with your healthcare provider before starting anything over the counter. Some health conditions or medications can be interfered with by taking various supplements.