Citrulline / L-Citrulline for Endurance
For aerobic endurance, the evidence indicates that citrulline (including citrulline malate) does not work: multiple meta-analyses and randomized trials consistently find no meaningful benefit on endurance capacity. It is graded Counter-Evidence because the highest-quality studies point clearly to a null effect.
Why this grade7-layer evidence engine
The grade rests on consistent negative findings at the top of the evidence hierarchy. Two systematic reviews with meta-analysis report essentially zero effect on aerobic endurance: pooled time-to-exhaustion SMD was 0.03 (95% CI -0.27 to 0.33) and time-to-completion SMD -0.07 in one analysis (PMID 37155582, n=158), while a second found aerobic-performance SMD 0.15 (p=0.08), with perceived exertion, VO2 kinetics, and blood lactate also non-significant (PMID 36079738). Because high-quality reviews are negative and concordant, lower-tier trials cannot overturn the verdict.
Randomized trials agree. An 8 g citrulline-malate crossover RCT showed no difference from placebo in time-to-exhaustion or power output (PMID 31994989, n=28), and a 2024 high-quality trial that directly compared L-citrulline, citrulline malate, and placebo found no benefit from either form (PMID 39662304, n=43). A critical review further noted that most citrulline-malate products failed quality control (roughly 1.1:1 to 1.6:1 malate ratio versus the labelled 2:1), confounding many earlier positive claims (PMID 34417881).
Regulators and health bodies offer no support. The EU EFSA position is unfavourable, with two Article 13(5) opinions concluding insufficient evidence of cause-and-effect and no authorised health claims; the US FDA lists citrulline only as a dietary-supplement ingredient with no endorsement, while the UK NHS and WHO do not address it, and NIH ODS and sports-nutrition guidance are cautious. Any positive signals are confined to short resistance or anaerobic repetition work, not aerobic endurance, and individual trials are small and acute, limiting generalizability.
Scoring transparency
All scores computed by a 7-layer evidence engine — fully auditable▸View the full decision path (audit trail)
- compute_raw_score — 加權公式: L2×0.30 + L3×0.25 + L5×0.25 + L11×0.10 + L1×0.10 = 0.462
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 negative 主導 (3 negative > 0 positive)，下層 RCT 不能推翻
- apply_hec_override — HEC-1 高階證據 negative — 強制由 C 改為 D
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status