L-Arginine

Supplements · Sports Performance · Supplement, Typed Supps

The original "pump" amino acid — though most of it never survives your gut.

Stage by stage

Intake (Capsule or powder): A significant portion is broken down by gut and liver enzymes before reaching circulation.
Small intestine (Partial breakdown): Absorbed, though much is metabolized before it reaches the bloodstream intact.
Bloodstream (Remaining portion circulates): The surviving portion is carried in the blood.
Blood vessels (Produces nitric oxide): Used to produce nitric oxide, widening blood vessels and increasing blood flow.

What the evidence supports

Lowering blood pressure — moderate evidence. Meta-analyses show modest reductions in systolic and diastolic blood pressure with oral supplementation.
Improving mild-to-moderate erectile dysfunction, often combined with other agents — limited evidence. Small trials at roughly 3–6 g/day report modest improvement; effects are inconsistent and often studied alongside other compounds.
Boosting the exercise 'pump' or performance — insufficient evidence. Results are inconsistent, and because arginine is poorly absorbed, citrulline is now generally preferred for raising arginine levels.

Typical dose

3–6 g/day in divided doses, on an empty stomach

Upper limit: No established UL; gastrointestinal upset practically limits high doses

Timing

Empty stomach, 30–60 minutes before exercise.

Time to effect

~1 hr: Acute blood-flow effect, when it survives digestion intact.

Medication interactions

Nitrates (e.g. glyceryl trinitrate): Additive blood-pressure lowering; risk of dangerous hypotension. (high)
PDE5 inhibitors (e.g. sildenafil, tadalafil): Additive blood-pressure lowering; risk of excessive hypotension. (high)
Antihypertensive medication: May lower blood pressure further, additively. (moderate)

Common myth

“Arginine is the best nitric oxide supplement available.” In reality: Because so much of an oral dose is broken down before absorption, citrulline has become more popular for reliably raising blood arginine levels.

Food sources

Pea Protein — Protein