HMB / Beta-Hydroxy Beta-Methylbutyrate for Muscle Gain
For the heavily marketed claim that HMB builds muscle and strength, the best independent evidence says it does not work in resistance-trained adults. The few positive trials come from industry-conflicted authors and have not been independently replicated, so the field only appears "disputed" on paper.
Why this grade7-layer evidence engine
This earns a Counter-Evidence (D) grade because the most direct, conflict-free studies are null. The largest independent meta-analysis in trained athletes (Sanchez-Martinez 2018, PMID 29249685, 6 RCTs, n=193) found trivial, non-significant effects on strength and fat-free mass (ES 0.00–0.16), and an independent academic review (Jakubowski 2020, PMID 32395175, 11 RCTs, n=302) confirmed no benefit to body composition or strength. An older meta-analysis (PMID 19387395) saw only a small strength signal in untrained lifters, with trivial effects once people were trained.
The grade reads as "disputed" only because two positive sources sit against these nulls, but both are compromised. Wilson 2014 (PMID 24599749) reported an implausible +7.4 kg lean-mass gain in 12 weeks; it was never independently replicated, and a 2017 critique (PMID 29209404) flagged data-integrity problems across linked papers. Its authors and the supportive ISSN position stand (PMID 39699070) carry HMB patents and MTI Biotech ties.
Regulators reinforce the skeptical read: the EU EFSA rejected all 12 HMB health claims for muscle mass and strength, finding no cause-and-effect relationship. One small crossover trial in combat athletes (PMID 28708126) showed modest gains, but any real-world benefit appears confined to untrained or clinical (elderly/sarcopenia) populations, not the general muscle-building use it is sold for.
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 = 0.282
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 內部嚴重矛盾 (2 positive vs 2 negative，各 ≥2)
- tier_strict_requirement_check — Tier 條件達標，未降階
- detect_disputes — 偵測到 1 個 hard + 0 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status