Quick answer: L-Citrulline is a non-essential amino acid that your body converts to L-Arginine, which then produces nitric oxide (NO). More nitric oxide means better blood flow, more oxygen to muscles, and improved exercise performance. It's one of the most effective and well-researched pre workout ingredients available.
What Is L-Citrulline?
L-Citrulline is an amino acid naturally produced by the body and found in foods like watermelon (its name comes from Citrullus, the Latin word for watermelon). While your body makes some citrulline on its own, supplemental doses significantly increase nitric oxide production beyond what your body can achieve naturally.
Here's how the pathway works:
- You take L-Citrulline
- Your kidneys convert it to L-Arginine
- L-Arginine is converted to Nitric Oxide (NO) by the enzyme nitric oxide synthase
- Nitric oxide relaxes blood vessels, increasing blood flow
This is why citrulline is more effective at raising arginine levels than taking arginine directly — oral arginine is heavily broken down by the liver before it reaches your bloodstream (called "first-pass metabolism"), while citrulline bypasses this entirely.
Benefits of L-Citrulline
Increased Blood Flow and Muscle Pumps
Citrulline's primary mechanism is boosting nitric oxide, which dilates blood vessels. This delivers more oxygen and nutrients to working muscles during exercise. The result: better endurance and the "pump" effect that signals increased blood volume in muscle tissue.
Improved Exercise Performance
Multiple studies show citrulline supplementation increases: - Total training volume (more reps before failure) - Time to exhaustion during endurance exercise - Power output during repeated high-intensity efforts
A 2010 study published in the Journal of Strength and Conditioning Research found that citrulline malate supplementation increased the number of bench press repetitions by 53% compared to placebo.
Reduced Muscle Soreness
The same study showed a 40% reduction in muscle soreness at 24 and 48 hours post-exercise. Better blood flow means faster clearance of metabolic waste products like ammonia and lactate.
Ammonia Clearance
Citrulline plays a role in the urea cycle, helping the body eliminate ammonia — a toxic byproduct of protein metabolism that contributes to fatigue during exercise.
Blood Pressure Support
Research shows citrulline supplementation can modestly reduce both systolic and diastolic blood pressure, likely through its nitric oxide-mediated vasodilation effects.
Clinically Effective Dosage
| Context | Dosage | Notes |
|---|---|---|
| Exercise performance | 3-6g L-Citrulline | Taken 30-60 min before training |
| If using Citrulline Malate | 6-8g | Contains ~56% citrulline by weight |
| Blood pressure support | 3-6g daily | Consistent daily use |
| Combined with L-Arginine | Lower doses effective in combination | Synergistic effect on NO production |
The Do Vitamins approach: PurePump® contains 2,000mg of Kyowa Hakko L-Citrulline paired with 500mg of AjiPure® L-Arginine per serving (2 scoops / 7.6g). That's 2,000mg of citrulline — below the 3-6g range studied for citrulline alone, and we're straightforward about that. The tradeoff is intentional: PurePump delivers 15 branded, active ingredients in a 7.6g serving that is 100% active compounds (zero filler, zero flavorings, zero sweeteners), prioritizing breadth and ingredient quality over mega-dosing any single ingredient.
The important number for nitric oxide production isn't citrulline alone — it's the combined citrulline + arginine total of 2,500mg feeding the NO pathway through two complementary mechanisms. Citrulline provides sustained arginine production (bypassing liver metabolism) while direct arginine provides an immediate substrate for NO synthesis. Research supports that this combination is more effective at raising nitric oxide than either amino acid alone at equivalent total doses.
L-Citrulline vs. Citrulline Malate
You'll see two forms on supplement labels:
| Form | What It Is | Pros | Cons |
|---|---|---|---|
| L-Citrulline | Pure citrulline amino acid | Full dose is active ingredient | — |
| Citrulline Malate | Citrulline bonded to malic acid (usually 2:1 ratio) | Malic acid may have its own benefits for energy production | Only ~56-67% citrulline by weight, so you need more |
If a label says "Citrulline Malate 6g," you're getting approximately 4g of actual citrulline. If it says "L-Citrulline 4g," you're getting 4g of actual citrulline. Read labels carefully.
PurePump uses pure L-Citrulline (Kyowa Hakko) — not citrulline malate — so every milligram on the label is active citrulline.
Why the Source Matters: Kyowa Hakko
Not all citrulline is created equal. Kyowa Hakko is a Japanese manufacturer that produces L-Citrulline through a patented fermentation process, ensuring:
- Pharmaceutical-grade purity — verified by independent testing
- Bioavailability — the L-form (not D-form) that your body can actually use
- Consistency — every batch meets the same standard
- Research backing — Kyowa Hakko citrulline is used in many of the clinical studies cited above
Generic citrulline from unverified sources may contain impurities, incorrect isomers, or underdosed active content. This is why branded ingredients matter.
Side Effects & Safety
L-Citrulline has an excellent safety profile. It's generally well-tolerated even at high doses.
Possible side effects (uncommon): - Mild stomach discomfort at very high doses (10g+) - May interact with nitrate medications or PDE5 inhibitors (both affect blood flow) — consult your doctor - May lower blood pressure — beneficial for most people, but worth monitoring if you already have low BP
No significant adverse effects have been reported in clinical studies at standard supplemental doses (3-8g/day).
How Do Vitamins Uses L-Citrulline
Product: PurePump® Pre-Workout L-Citrulline per serving: 2,000mg (Kyowa Hakko) | Serving size: 2 scoops (7.6g) | Servings per container: 30
PurePump contains 2,000mg of Kyowa Hakko L-Citrulline plus 500mg of AjiPure L-Arginine per serving — a combined 2,500mg feeding nitric oxide production through two complementary pathways: sustained production via citrulline-to-arginine conversion and immediate substrate availability via direct arginine.
Honest context on dosing: 2,000mg of L-Citrulline is below the 3-6g range used in most standalone citrulline studies. We won't pretend otherwise. PurePump's formulation philosophy prioritizes breadth — 15 branded active ingredients with zero filler — over mega-dosing any single one. The entire 7.6g serving is active ingredients. Every gram is accounted for, and the combined citrulline + arginine pathway support (2,500mg total) is the relevant number for NO production. For athletes who want higher citrulline doses, standalone Kyowa Hakko L-Citrulline can be stacked alongside PurePump.
Unlike many pre workouts that use generic citrulline malate (getting you less actual citrulline per gram), PurePump uses pure L-Citrulline from one of the world's most respected amino acid manufacturers.
Every batch of PurePump is tested by the Banned Substance Control Group (BSCG), ensuring the citrulline you're taking is exactly what's on the label — no more, no less, no contaminants.
FAQ
Is citrulline better than arginine?
For raising blood arginine levels, yes. Oral L-Citrulline is more effective than oral L-Arginine because it bypasses liver metabolism. However, the best approach is to take both together (as PurePump does) for maximum nitric oxide production.
When should I take citrulline?
30-60 minutes before exercise for performance benefits. It can also be taken daily for blood pressure and cardiovascular support.
Can I get enough citrulline from food?
Watermelon is the richest food source, but you'd need to eat several pounds per day to match a supplemental dose. Supplementation is the practical choice for performance benefits.
Does citrulline cause tingling?
No. The tingling sensation associated with pre workouts comes from beta-alanine, not citrulline. Citrulline has no noticeable sensation.
Is citrulline safe to take every day?
Yes. Studies show no adverse effects from daily citrulline supplementation at standard doses. It's one of the safest and best-tolerated sports nutrition ingredients.
What's the difference between Kyowa Hakko citrulline and generic citrulline?
Kyowa Hakko produces L-Citrulline through a patented fermentation process with pharmaceutical-grade quality controls. Generic citrulline may come from less regulated sources with less consistent purity and potency.
These statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.
