Conjugated Linoleic Acid (CLA) for Muscle Gain
For building muscle, conjugated linoleic acid (CLA) shows only a tiny, disputed signal in lean mass that researchers themselves call clinically questionable. It is not an effective muscle-building supplement, and major regulators have rejected related body-composition claims.
Why this grade7-layer evidence engine
The grade is Weak (and flagged as Disputed) because the data point in one direction but barely move the needle. The largest pooled analysis, a 2024 meta-analysis of 70 trials (n=4,159, PMID 37671495), found CLA raised fat-free mass by just +0.27 kg (P=0.003) — a result its own authors say may not be clinically important. A long-term meta-analysis (PMID 21990002) likewise concluded there was no convincingly meaningful body-composition effect.
The few clearly positive results come from small, short studies: a 12-week trial in 48 adults with obesity (+0.64 kg lean mass, PMID 17449580) and a 7-week resistance-training trial in 76 people (+1.4 vs +0.2 kg, PMID 16531905). These were mostly overweight or obese cohorts on 5–6 g/day, so they say little about healthy people training for muscle, and durability beyond three months is unknown.
Authoritative bodies do not back this use. The EU's EFSA explicitly rejected the claim that CLA increases lean body mass, judging the causal link unproven, while the US FDA treats CLA only as a generally-recognized-as-safe food ingredient, not an effective supplement. Mayo Clinic, Cleveland Clinic and Harvard Health do not address it, and a sports-nutrition society review called the clinical evidence insufficient and inconsistent, with documented side effects. This clash between a marginal benefit and regulatory rejection is why the verdict is disputed.
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 = 0.607
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (1 篇 > 0 negative)
- tier_strict_requirement_check — | B→C 因 scope.conflation_risk=true 且 L11 獨評較低 (B7-2 tier cap)
- detect_disputes — 偵測到 1 個 hard + 1 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status