Discovered in watermelon in 1914 by Japanese chemists, citrulline is a non-essential amino acid produced by the body and vital to the urea cycle. In recent years, its popularity as a sports supplement has surged, backed by research showing benefits for vasodilation, muscle development, and endurance—making it a staple for bodybuilders and athletes.
Citrulline, first isolated from watermelon, is non-essential since the body synthesizes it naturally. You can boost levels through citrulline-rich foods or supplements, enhancing health and athletic performance, particularly in bodybuilding.
Unlike protein-building amino acids, citrulline excels in vasodilation—widening blood vessels to lower blood pressure and improve flow. Upon ingestion, it converts to arginine, then nitric oxide, relaxing vessel walls for better circulation.
This nitric oxide surge boosts blood flow, delivering more oxygen and nutrients to muscles—key for performance gains. Though not directly used in protein synthesis, citrulline activates pathways that promote muscle protein synthesis while curbing breakdown, supporting mass gains and maintenance.
For bodybuilders, citrulline's vasodilation increases nutrient and oxygen delivery to muscles, fueling energy production, recovery, and muscle fiber health post-workout. It may also enhance brain blood flow, sharpening focus, adaptation, and concentration—a natural alternative to caffeine pre-workouts.
Research supports citrulline's safety even at high doses. In one study, eight healthy men took 2g, 5g, 10g, or 15g of L-citrulline on separate occasions, reporting no side effects. Doses over 10g offered no extra arginine boost, indicating an optimal range. Blood tests showed no adverse effects on vital functions or pressure.
