amino-acidEVIDENCEBUSOTC

L-Arginine

aka Arginine

Conditionally essential amino acid; the direct precursor to nitric oxide. Used for cardiovascular function and erectile dysfunction.

Dose range3000–6000mg

Half-life—h

Onset—min

Safety4/5high evidence base

Mechanism of action

Direct substrate for nitric oxide synthase (NOS), producing nitric oxide that mediates vasodilation, blood pressure regulation, and many endothelial functions. Oral L-arginine has poor bioavailability compared to L-citrulline (which converts to arginine in the kidneys); citrulline produces more reliable plasma arginine elevation per dose.

History

L-arginine was isolated in 1886 from lupin sprouts. Its role in nitric oxide synthesis was characterised in the 1980s, leading to the 1998 Nobel Prize for the NO discoveries. The cardiovascular and erectile dysfunction applications followed. Modern preference for L-citrulline as the more reliable oral source has displaced direct L-arginine supplementation in many protocols. Unscheduled globally.

Benefits

Cardiovascular function
EVIDENCEB
Multiple trials.
Erectile dysfunction (combined)
EVIDENCEB
Multiple RCTs.
Exercise performance
EVIDENCEC
Mixed evidence; L-citrulline is more reliable.

Side effects

GI upsetcommonmild
Worsens herpes outbreaks (lysine balance)uncommonmoderate

Cited research

L-arginine for erectile dysfunction: meta-analysis (Rhim)2019
PMID 30817953 ↗
L-arginine for cardiovascular function (Pollock)2013
PMID 23735312 ↗
L-arginine vs L-citrulline pharmacokinetics (Schwedhelm)2008
PMID 18230204 ↗

Where to buy

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Vendor	Product	Size	Price	Per unit
Double Wood Supplements 4.4	L-Arginine — Double Wood	—	See vendor	—	Shop Ad
BulkSupplements 4.2	L-Arginine — BulkSupplements	—	See vendor	—	Shop Ad
NOW Foods 4.1	L-Arginine — NOW Foods	—	See vendor	—	Shop Ad
Amazon Marketplace 3.5	L-Arginine — Amazon	—	See vendor	—	Shop Ad

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