L-Arginine for Athletes: Does It Really Boost Performance?

review PMID: 40733000

Quick Summary: A recent study looked at the research on L-arginine, a popular supplement for athletes. It found that previous studies claiming L-arginine boosts performance might have been flawed, and the benefits are likely much smaller than originally thought.

What The Research Found

The original research suggested L-arginine could improve athletic performance. However, this new analysis found that the original study had some errors. When the errors were corrected, the benefits of L-arginine seemed much less significant. The corrected analysis showed that L-arginine might not provide a noticeable performance boost.

Study Details

Who was studied: The original research looked at data from 24 different studies. These studies included a total of 498 athletes, both men and women, with an average age between 23 and 35.

How long: The athletes in the original studies took L-arginine for varying lengths of time, from just before exercise to several months.

What they took: Athletes took L-arginine in doses ranging from 1 to 12 grams per day, usually in pill or powder form.

What This Means For You

If you're an athlete considering L-arginine, this research suggests you might not see the performance gains you're hoping for. It's important to be skeptical of claims about supplements and look for solid evidence. Focus on proven methods like proper training, nutrition, and recovery.

Study Limitations

The new analysis only looked at the data from the original studies. It couldn't access the raw data. Also, the original studies might have had some issues, like not including all relevant research or not accounting for differences between studies. This means the results should be interpreted with caution.

Key Findings

This critical review identifies methodological flaws in Viribay et al.’s 2025 meta-analysis on L-arginine supplementation and athletic performance. The original study reported a moderate pooled effect size (SMD 0.42, p=0.003), but after correcting errors in trial selection, statistical pooling, and data extraction, the recalculated effect size dropped to 0.18 (p=0.10, 95% CI -0.04 to 0.40), rendering it nonsignificant. The authors conclude that Viribay et al.’s findings were distorted by inconsistent inclusion criteria, failure to account for heterogeneity, and inappropriate handling of overlapping data from multi-arm trials.

Study Design

This is a systematic review and meta-analysis comment published in Nutrients (2025). It reanalyzed Viribay et al.’s dataset, which included 24 randomized controlled trials (RCTs) involving 498 athletes (70% male, 30% female; mean age 23–35 years). The original analysis pooled outcomes across diverse exercise types (aerobic, anaerobic, resistance training) and durations (4 weeks to 6 months).

Dosage & Administration

The original meta-analysis evaluated L-arginine doses ranging from 1–12g/day, administered primarily via oral tablets or powders. Supplementation durations varied from acute pre-exercise dosing (≤1 hour) to chronic regimens (≥4 weeks). The comment notes that Viribay et al. did not stratify results by dosage or timing, potentially conflating acute and long-term effects.

Results & Efficacy

Viribay et al. initially found L-arginine improved performance metrics like time-to-exhaustion and power output (SMD 0.42, p=0.003). However, after excluding trials with overlapping cohorts and applying random-effects models to account for heterogeneity (I²=62%), the corrected SMD was 0.18 (p=0.10). Subgroup analyses revealed no significant benefits for aerobic capacity (VO₂ max: SMD 0.11, p=0.25) or strength (1RM: SMD 0.23, p=0.15). Confidence intervals for corrected estimates crossed zero, indicating uncertainty in true efficacy.

Limitations

The original meta-analysis suffered from selection bias (excluding non-English studies), failure to adjust for multiple comparisons in multi-arm trials, and inconsistent blinding of outcome assessors. The comment authors acknowledge their analysis is limited to re-evaluating published data without access to raw datasets. Additionally, Viribay et al.’s pooled estimates may have been inflated by small-study effects (Egger’s test p=0.03), suggesting publication bias. Future research requires standardized protocols for dosing, exercise modalities, and reporting.

Clinical Relevance

For athletes and practitioners, these findings caution against overinterpreting prior claims about L-arginine’s performance-enhancing effects. The corrected analysis suggests minimal benefits, particularly when methodological rigor is applied. Users should prioritize well-controlled trials and consider individual variability in response to supplementation. The study underscores the importance of critically appraising meta-analyses for methodological transparency before applying conclusions to real-world settings.