L-Citrulline vs L-Arginine: The Bypass
Both supplements aim to increase Arginine levels in the blood. Arginine converts to Nitric Oxide (NO), which widens blood vessels ("The Pump").
The irony is that taking L-Arginine is the worst way to increase Arginine. Taking L-Citrulline is far more effective.
| Feature | L-Citrulline | L-Arginine |
|---|---|---|
| Blood Arginine Levels | High Increase | Low Increase |
| Metabolism | Bypasses Liver (Kidneys) | Destroyed by Arginase in Liver |
| Stomach Upset | Rare | Common (Diarrhea) |
| Cost | Moderate ($$) | Cheap ($) |
Mechanisms: The First Pass Effect
L-Arginine: The Victim
When you swallow L-Arginine, it goes to the liver. An enzyme called Arginase breaks most of it down before it ever reaches your muscles.
It also draws water into the gut, which often causes "disaster pants" at effective dosages (5g+).
L-Citrulline: The Survivor
L-Citrulline is not recognized by Arginase. It passes the liver untouched and travels to the kidneys.
The kidneys then convert it into L-Arginine and release it into the blood. This results in higher, more sustained arginine levels than taking arginine itself.
What it means
It is a "trojan horse." It sneaks past the liver's defenses to deliver the goods.
Which One Matches Your Goal?
For Gym Pumps
Winner: L-Citrulline (or Citrulline Malate).
Studies consistently show Citrulline improves reps to failure and reduces muscle soreness. Arginine studies are mixed at best.
For Blood Pressure
Winner: L-Citrulline.
By effectively boosting Nitric Oxide, Citrulline helps relax stiff arteries and lower blood pressure over time.
The Verdict
Choose L-Citrulline if: You want results. It is superior in every single metric.
Choose L-Arginine if: You enjoy wasting money or have a specific metabolic disorder that prevents Citrulline conversion (rare).