Casein for Muscle Gain
Casein is a high-quality complete protein that supports muscle gain when it helps you reach your daily protein target, and a pre-sleep dose may aid overnight muscle recovery. However, the evidence does not show casein outperforming whey or other proteins when total protein intake is matched.
Why this grade7-layer evidence engine
This earns a moderate (A) grade because the supporting evidence is consistent but largely shows that casein works as protein, not as something uniquely better. A 2018 meta-analysis (PMID 28698222, n=1,863) found that protein supplementation, pooling sources including casein, raised fat-free mass by about 0.30 kg and strength by 2.49 kg over placebo. A 2013 head-to-head RCT (PMID 24149728) reported essentially identical lean-mass gains for casein versus whey when the dose was equated, and a 2026 network meta-analysis (PMID 41635649, n=4,755) ranked whey as significant for fat-free mass and strength while casein lacked enough independent trials to rank on its own.
The most-cited reason to choose casein specifically is its slow digestion and a pre-sleep timing strategy. This is biologically plausible and partly supported: a 12-week RCT (PMID 25926415) found greater quadriceps growth and strength with 27.5 g of casein before bed, and mechanistic trials (PMID 27643743, PMID 36857005) confirm that pre-sleep protein boosts overnight muscle protein synthesis. The catch is that the 12-week trial used a calorie-free placebo rather than a protein-matched control, so part of the benefit likely reflects extra total protein, and PMID 36857005 found casein and whey worked equally well.
Regulators and clinics back casein's quality but not a specific muscle claim. The US FDA recognizes casein as GRAS for use as a nutrient supplement, and the WHO/FAO Codex framework uses it as the top protein-quality benchmark (a perfect PDCAAS score of 1.0). The Mayo Clinic lists casein only as one acceptable complete-protein option, noting that resistance training and adequate whole-food protein matter more than any single supplement. Bottom line: casein is a legitimate tool for hitting protein goals and supporting training, but its evidence for a casein-specific advantage remains limited.
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 = 0.715
- tier_from_score — 依分數區間映射至 tier letter
- apply_hec_rules — 高品質 SR/MA 顯示 positive (2 篇 > 0 negative)
- 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