What do the states mean?+
- Solid: well studied, and it works.
- Half-there: the science is still forming.
- A ghost: almost no real studies.
- Hollow: well studied, and it does not work.
- A cord: the pair itself has been tested together.
- Air: nobody has ever tested this pair.
The full scoring method: How we score
L-arginine benefits: where the science stands
For endurance: not settled yet.
Endurance is what most people take L-arginine for, and the best studies disagree: one found it helps, one found no effect. As of August 2026, the verdicts on this page rest on evidence from 110 trials, drawn from the strongest research among the 2,502 papers on PubMed that mention L-arginine. Every claim is checked below.
2,502 papers on PubMed · evidence from 110 trials · 1 caution
Claim by claim
- EnduranceThe science is still forming. The best studies disagree.
- Asthma and breathingThe science is still forming. No real difference found so far.
- Blood pressureThe science is still forming. Results lean positive, but there is not much yet.
- CholesterolThe science is still forming. No real difference found so far.
See 11 more scored claims+
- Gut and digestionThe science is still forming. The best studies disagree.
- HeartWell studied, and it does not work. The biggest review covered 13 trials.
- Immunity and coldsThe science is still forming. The best studies disagree.
- InflammationThe science is still forming. No real difference found so far.
- Performance and vitalityThe science is still forming. No real difference found so far.
- PregnancyAlmost no real studies. What exists leans positive.
- Sprint and repeated-effort powerThe science is still forming. Results lean positive, but there is not much yet.
- Strength and powerThe science is still forming. A safety question was raised; later testing found no change.
- Testosterone and libidoThe science is still forming. Results lean positive, but there is not much yet.
- Weight and body fatWell studied, and it does not work. The biggest review covered 8 trials.
- Wound healingThe science is still forming. The best studies disagree.
Pairs people ask about
The 26 sources we read
- 2006Randomized trial · 35 people · no clear effect on endurance; benefit for sprint and repeated-effort power; benefit for strength and power; no clear effect on weight and body fatsource
- 2009Meta-analysis · pools 2 trials, 927 people · no clear effect on heartsource
- 2011Crossover trial · 12 people · a harm signal on strength and powersource
- 2013Randomized trial · 83 people · no clear effect on gut and digestionsource
- 2014Meta-analysis · pools 11 trials, 321 people · moderate benefit for immunity and coldssource
- 2016Meta-analysis · no clear effect on performance and vitalitysource
- 2017Meta-analysis · pools 3 trials, 285 people · large benefit for gut and digestionsource
- 2018Randomized trial · 20 people · no clear effect on strength and powersource
- 2018Meta-analysis · pools 13 trials · no clear effect on heartsource
- 2019Meta-analysis · no clear effect on cholesterolsource
- 2019Meta-analysis · pools 11 trials · no clear effect on inflammationsource
- 2020Meta-analysis · large benefit for endurance; small benefit for sprint and repeated-effort powersource
- 2020Meta-analysis · no clear effect on weight and body fatsource
- 2020Meta-analysis · no clear effect on heartsource
- 2020Crossover trial · 50 people · no clear effect on asthma and breathingsource
- 2021Meta-analysis · pools 8 trials · no clear effect on weight and body fatsource
- 2021Meta-analysis · pools 5 trials · benefit for wound healingsource
- 2022Randomized trial · 48 people · no clear effect on inflammation; no clear effect on weight and body fatsource
- 2022Randomized trial · 74 people · no clear effect on immunity and coldssource
- 2022Meta-analysis · pools 22 trials · moderate benefit for blood pressuresource
- 2024Meta-analysis · benefit for testosterone and libidosource
- 2025Randomized trial · 100 people · no clear effect on cholesterol; benefit for heartsource
- 2025Meta-analysis · pools 15 trials, 1,085 people · no clear effect on wound healingsource
- 2025Randomized trial · 69 people · benefit for wound healingsource
- 2025Meta-analysis · pools 4 trials · moderate benefit for pregnancysource
- 2026Crossover trial · 16 people · no clear effect on strength and powersource
Chosen as the strongest evidence out of 2,502 papers on PubMed. Every row links to its paper.
Fair questions
Does L-arginine work?+
For endurance, it is not settled. The best studies disagree.
Is L-arginine safe?+
One caution is recorded: Searching 21 health outcomes returned no trial of L-arginine on its own for any of them. This is not the same as a supplement nobody has studied. L-arginine is a nutrient your body needs, and there is research on it. What that research is about is multi-antioxidant fertility formulations and clinical nutrition, rather than arginine taken alone. None of it tells you whether taking extra helps someone who already gets enough.
Why only 26 sources, when PubMed lists 2,502?+
The 2,502 is every paper that mentions L-arginine in any way: animal studies, blood measurements, papers where it is a side note. The strongest sources are combined reviews, and each one already gathers every trial its authors could find. Our 26 cover 110 trials between them, and every one is linked above. Both counts are measured, not estimated.