Short answer: L-Citrulline is absorbed intact and converted to L-Arginine in the kidneys, sidestepping the gut-and-liver breakdown that limits arginine taken alone.
Why naming the kidneys specifically matters
This gives you a precise, checkable location for this conversion step, distinct from a vague "gets processed by the body" claim.
Why this is presented as Step 2 in a specific, six-step mechanism
Step 1 (amino acids enter the cycle) precedes this kidney-conversion step, which then leads directly into Step 3 (vessels relax) — a genuinely sequential, detailed explanation.
💡 Worth knowing: the manufacturer's own simplified overview compresses this into just four steps — this specific kidney-conversion detail is the piece that overview skips.