Much like L-Arginine, L-Citrulline improves levels in the body nitric oxide. That’s because L-Citrulline is a precursor to L-Arginine. So why not just take L-Arginine? Well you could, but the advantage of L-Citrulline is that it doesn’t get eliminated in the gut or liver like L-Arginine. Instead, it is metabolized to L-Arginine in the kidneys, which is then converted to nitric oxide. Thus promoting the same things: an increase in endurance, performance, blood flow, and recovery.