L-Arginine for Exercise Performance

Research suggests that L-arginine supplementation has limited direct evidence for improving exercise performance in humans, with a 2023 narrative review finding that typical doses did not meaningfully enhance physical performance or increase nitric oxide production in either recreational or trained athletes. Studies indicate that whatever benefits exist in the nitric oxide pathway appear more reliably attributed to dietary nitrate sources like beetroot and, to some extent, L-citrulline rather than L-arginine itself, a finding echoed across multiple reviews and a 2021 meta-analysis of 118 randomized controlled trials. Some supportive animal research, including a 2024 mouse study showing improved endurance and muscle fiber composition changes and a 2017 rat study showing performance gains with supplementation, offers mechanistic interest but cannot be directly applied to human athletic populations. Overall, the body of evidence leans toward neutral to unsupportive for L-arginine as a standalone exercise performance aid in humans, with researchers noting that responses may vary by fitness level, sex, and study design, and that further well-controlled human trials are needed before stronger conclusions can be drawn.