L-Arginine
Unproven· human dataAlso known as: Arginine
A nitric-oxide precursor whose pump-and-performance claims are undercut by poor absorption.
Arginine is a precursor to nitric oxide, which is the basis for its marketing as a blood-flow and 'pump' aid. The problem is absorption: oral arginine is largely broken down in the gut and liver, so it raises blood arginine surprisingly poorly.
In controlled trials it generally fails to improve performance in healthy trainees. Ironically, supplementing citrulline raises blood arginine more effectively, which is why citrulline has largely displaced arginine as the sensible choice for this purpose.
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Written and reviewed by Mathew Beale, MSc Biotechnology, University of Reading.
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