L-Arginine

What Is L-Arginine?

L-Arginine is a conditionally essential amino acid that acts as the direct substrate for nitric-oxide synthase, producing nitric oxide (NO), a key vasodilator. Through this NO pathway it is taken for blood-flow support, blood-pressure reduction, and the exercise “pump.” The cardiovascular/blood-pressure literature is the better-evidenced part of its record; the sports-performance and “pump” claims are more mixed, partly because oral arginine has modest, variable bioavailability (which is why L-citrulline is often preferred for raising plasma arginine).

Evidence

The strongest signal is on blood pressure. A 2022 systematic review and dose-response meta-analysis of randomised clinical trials found that L-arginine supplementation significantly lowered both systolic and diastolic blood pressure, with the effect concentrated at moderate doses and no additional benefit above roughly 9 g/day ^{1Reference 1Torabi M et al. · 2022Meta-analysisEffect of L-arginine supplementation on blood pressure in adults: a systematic review and dose–response meta-analysis of randomised clinical trials — meta-analysisView study →}. This is consistent with its NO-precursor mechanism. Direct ergogenic (“pump,” strength, endurance) claims are widely made but were not backed by a clearly positive, verified meta-analysis in this quick pass; the performance evidence for arginine specifically is inconsistent and should be treated as unproven pending a fuller review.

Dosage & Safety

Blood-pressure trials generally used oral doses in the range of about 4–9 g/day ^{1Reference 1Torabi M et al. · 2022Meta-analysisEffect of L-arginine supplementation on blood pressure in adults: a systematic review and dose–response meta-analysis of randomised clinical trials — meta-analysisView study →}; this is informational and not a personal recommendation. Toxicity appears low, but because arginine can lower blood pressure, combining it with antihypertensive drugs could have additive effects, and caution is warranted in people recovering from a recent heart attack (a trial in post-MI patients raised safety concerns). Full drug-interaction, upper-limit, and pregnancy/lactation data were not established or fully assessed in this pass.

References

1. Torabi M, et al. (2022). Effect of L-arginine supplementation on blood pressure in adults: a systematic review and dose–response meta-analysis of randomised clinical trials — meta-analysis. Adv Nutr. https://pubmed.ncbi.nlm.nih.gov/34967840/