A1
L-citrulline
- Product declaration
- L-Citrulline: 10 g
- 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
L-arginine
- Product declaration
- L-Arginine: 1.25 g
- Selected studied range
- 2000 to 20000 mg
- Protocol and duration
- per day across the studies NIH ODS reviewed
- Studied context
- Plain L-arginine has been studied for exercise-related vasodilation, blood flow, and exercise metabolites, per NIH ODS. The branded ingredient Nitrosigine (inositol-stabilized arginine silicate) has been studied in a series of company-funded and academic trials for acute and sustained plasma arginine elevation, exercise-induced muscle damage markers (serum creatine kinase), perceived energy, and post-exercise cognitive performance. A randomized double-blind study (PMC5133120) reported cognitive-test-score changes (including RBANS measures) in healthy physically active adults.
- Limitations
- NIH ODS states plain arginine supplementation shows "little to no effect on vasodilation, blood flow, or exercise metabolites" and "little to no enhancement of athletic performance" overall. A notably weak evidence verdict for the free amino acid form. For Nitrosigine specifically, this research pass relied on the trademark holder's own technical page and holder-affiliated trial write-ups (A3-level sourcing); no independent NIH/FDA/EFSA evaluation of Nitrosigine's efficacy claims was located.
Selected evidence: NIH ODS, Dietary Supplements for Exercise and Athletic Performance · Open source
A2
Beta-alanine
- Product declaration
- Beta Alanine: 3.2 g
- Selected studied range
- 4000 to 6000 mg
- Protocol and duration
- per day in divided doses, for at least 2 to 4 weeks, not as a single pre-workout dose
- Studied context
- Studied for high-intensity exercise capacity in the 60-240 second range via elevation of muscle carnosine, which acts as an intracellular pH buffer against acidosis. ISSN 2015 position stand: greatest performance benefits in "open end-point" tasks/time trials lasting 1-4 minutes; some benefit noted in aerobic exercise up to roughly 25 minutes; attenuation of neuromuscular fatigue, particularly noted in older adults.
- Limitations
- Strength/resistance-training outcomes remain mixed; training volume may increase without a clear strength gain. Tasks under 60 seconds do not show benefit. Endurance benefit beyond about 25 minutes is not established. Long-term safety data beyond roughly a year, and effects in special/tactical populations, are flagged as needing more research.
Selected evidence: ISSN position stand on beta-alanine, 2015 · Open source
A1
Betaine anhydrous
- Product declaration
- Betaine [from betaine nitrate NO3-T (1.6 g), trimethylglycine (1.5 g)]: 2.5 g
- 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: 2 g
- 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
L-tyrosine
- Product declaration
- L-Tyrosine: 1.5 g
- Selected studied range
- 2000 to 2000 mg
- Protocol and duration
- per day for five days, in the cadet study
- Studied context
- Studied as the dietary precursor to norepinephrine for mitigating cognitive performance decrements under acute stress. A 2015 Military Medicine evidence review (rapid evidence assessment, 14 trials: 10 RCTs + 4 controlled clinical trials) issued a "weak recommendation" in favor of tyrosine for cognitive stress specifically, stating "all studies showed a positive effect" on that outcome. A widely cited primary study (Deijen et al. 1999, Brain Research Bulletin) gave cadets 2 g tyrosine daily for five days during a combat training course and found better memory and tracking-task performance, plus lower systolic blood pressure, versus a carbohydrate control.
- Limitations
- The 2015 Military Medicine review states explicitly that "no recommendation could be made" for tyrosine's effect on physical performance under stressful physical conditions, and concludes "available evidence is insufficient to make confident recommendations on the effectiveness of tyrosine for mitigating stress effects on physical/cognitive performance" overall, despite the positive signal on cognition. A separate heat-stress study found tyrosine ingestion did not influence cognitive function or physical performance during exercise heat stress despite raised serum tyrosine. NIH ODS's exercise/athletic-performance fact sheet does not cover tyrosine at all.
Selected evidence: Deijen et al., Brain Research Bulletin, 1999
A1
Choline bitartrate
- Product declaration
- Choline Bitartrate (Vitacholine): 550 mg
- Selected studied range
- 425 to 550 mg
- Protocol and duration
- Adequate Intake for adults, a nutrient reference and not an ergogenic dose
- Studied context
- NIH ODS's Choline Health Professional fact sheet establishes choline's core physiological roles: synthesis of phosphatidylcholine and sphingomyelin for cell-membrane structure, acetylcholine (a neurotransmitter for memory, mood, and muscle control) production, methyl-group donation, gene-expression modulation, and brain development. Choline bitartrate is named as one of three supplement forms (with phosphatidylcholine and lecithin).
- Limitations
- NIH ODS states explicitly: "No studies have compared the relative bioavailability of choline from these different forms". Meaning choline bitartrate's absorption/efficacy relative to phosphatidylcholine, lecithin, or non-bitartrate forms (like alpha-GPC) is not established by NIH's own review.
Selected evidence: NIH ODS, Choline fact sheet · Open source
A2
Vincamine
- Product declaration
- Vincamine: 20 mg
- Selected studied range
- No dose range selected
- Protocol and duration
- Not recorded in the selected comparison
- Studied context
- Vincamine has been studied as a pharmacologically active alkaloid in older human clinical and pharmacokinetic research. Those studies are not pre-workout efficacy studies and do not establish a dietary-supplement dose range.
- Limitations
- The product label does not establish pharmaceutical formulation, purity, or equivalence to the preparations in the older studies. No sports-performance benefit is established by the cited sources.
Selected evidence: Severe ventricular arrhythmia following parenteral administration of vincamine · Open source