HMB / Beta-Hydroxy Beta-Methylbutyrate for Sarcopenia
HMB shows a small, fairly consistent benefit for handgrip strength in older adults with sarcopenia, but its effects on muscle mass are borderline and inconsistent, and it does not reliably improve physical function. The overall evidence is weak, and no major regulator or specialty society endorses it for this use.
Why this grade7-layer evidence engine
Recent meta-analyses converge on a small signal for one outcome only: a 2024 analysis found grip strength improved (MD 1.26 kg) while gait speed, fat mass, fat-free mass, and skeletal muscle index did not (PMID 39071082), and a 2025 analysis found grip strength (SMD 0.65) and a borderline muscle-mass gain (SMD 0.32, p=0.048, CI touching zero) but no physical-performance benefit (PMID 39999663). A 2023 RCT mirrored this, improving grip, gait, and chair-stand time but not muscle mass (PMID 37248756).
Earlier work is encouraging but thin. A 2021 meta-analysis found a fat-free-mass effect (SMD 0.37) that vanished when HMB was combined with exercise (PMID 33034021), an odd result given exercise is the proven core treatment. A 2019 review (PMID 30697623) pooled just three RCTs, and the mechanistically strongest bed-rest RCT preserved lean mass but enrolled only 19 people (PMID 23514626), so it cannot be generalized to community-dwelling older adults.
Regulatory and clinical backing is absent to negative. EFSA rejected all of HMB's muscle-related health claims, finding no established cause-and-effect; the US FDA grants it no approved claim, and the UK NHS and WHO do not address it. NIH ODS and the sarcopenia specialty guidance are cautious, rating the evidence very limited with no formal recommendation. With small, heterogeneous trials, undisclosed industry funding, and benefits confined to a secondary outcome, the weak grade is appropriate.
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 = 0.553
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (3 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 0 個 hard + 2 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status