A1
L-citrulline
- Product declaration
- L-Citrulline: 5000 mg
- Selected studied range
- 3000 to 9000 mg
- Protocol and duration
- per day, in the studies NIH ODS summarizes
- Studied context
- Studied as a nitric-oxide pathway precursor (converted to arginine via the urea cycle) for aerobic exercise performance measures such as oxygen-uptake (VO2) kinetics, blood lactate, and rate of perceived exertion, and for acute resistance-exercise performance and muscle oxygenation. NIH ODS describes evidence for enhancing performance as limited, with few studies and conflicting results.
- Limitations
- A 2022 systematic review/meta-analysis found no significant benefit for endurance-performance outcomes specifically. A single 8 g acute dose did not enhance isometric force production, muscle endurance, or muscle-oxygenation parameters in one resistance-exercise study. NIH ODS characterizes overall performance-enhancement evidence as limited.
Selected evidence: NIH ODS, Dietary Supplements for Exercise and Athletic Performance · Open source
A1
Betaine anhydrous
- Product declaration
- Betaine Anhydrous: 2000 mg
- Selected studied range
- 2000 to 5000 mg
- Protocol and duration
- per day, studied for up to 15 days
- Studied context
- NIH ODS describes betaine as studied for strength- and power-based performance in bodybuilders and cyclists, with "potential but modest" improvements from a limited set of small, sometimes conflicting studies. A 2024/2025 systematic review focused specifically on endurance performance (VO2max, time-to-exhaustion, time-to-completion, power output).
- Limitations
- The endurance systematic review explicitly states "limited and inconclusive evidence regarding the definitive ergogenic effect of betaine supplementation on endurance exercise performance". Only 2 of 5 reviewed studies showed a significant improvement, and the authors call for "additional, more rigorous research."
Selected evidence: NIH ODS, Dietary Supplements for Exercise and Athletic Performance · Open source
A2
Taurine
- Product declaration
- Taurine: 1500 mg
- Selected studied range
- 1000 to 3000 mg
- Protocol and duration
- per day, acutely across 6 to 15 days
- Studied context
- Studied for aerobic performance (VO2max, time-to-exhaustion, time-trial performance), anaerobic/strength performance, exercise-induced muscle damage, and recovery. A 2018 review ("Taurine in sports and exercise," PMC8152067) reports small-to-moderate improvements across several of these outcomes in some studies.
- Limitations
- The 2018 review states plainly: "limited and varied findings prohibit definitive conclusions regarding the efficacy of taurine on aerobic and anaerobic performance," and separately notes no peer-reviewed evidence exists for an independent role of taurine in skeletal-muscle hypertrophy.
Selected evidence: Taurine in sports and exercise, 2018 · Open source
A2
Agmatine sulfate
- Product declaration
- Agmatine Sulfate: 500 mg
- Selected studied range
- No dose range selected
- Protocol and duration
- Not recorded in the selected comparison
- Studied context
- Human data is comparatively sparse. A randomized double-blind placebo-controlled trial studied oral agmatine sulfate (1,335-3,560 mg/day for up to 3 weeks) for lumbar disc-associated radiculopathy (a clinical/pain context, not sports performance). A 2019 Scientific Reports paper examined safety and neurochemical profiles of acute and sub-chronic oral agmatine sulfate treatment.
- Limitations
- Sports-performance-specific human efficacy data for agmatine sulfate (e.g., a dedicated ISSN position stand) was not located in this research pass. Evidence located centers on safety/tolerability and non-sports clinical contexts rather than an authoritative performance-outcome verdict. Long-term safety in larger populations remains an open gap per the safety literature reviewed.
Selected evidence: Safety and neurochemical profiles of oral agmatine sulfate, 2019 · Open source