L-Arginine

Tier 2 — promising · Blood flow · Erectile function · Blood pressure

An amino acid that your body converts into nitric oxide, which relaxes blood vessels. Multiple trials show it modestly lowers blood pressure and improves erectile function. However, L-citrulline actually raises blood arginine levels more effectively than arginine supplements themselves. May cause digestive upset at doses above 6 g. Avoid after a heart attack as the VINTAGE-MI trial showed increased mortality.

Dose: 3–6 g/day in divided doses; L-citrulline may be more effective; AVOID after recent heart attack