Casein for Exercise Recovery
Casein taken before sleep modestly supports overnight muscle recovery after exercise, but the benefit comes from adding protein at night rather than from casein itself, which performs no better than other high-quality proteins when the protein dose is matched.
Why this grade7-layer evidence engine
The grade is Preliminary (B) because a small but consistent body of randomized trials shows a real, modest effect. In a crossover RCT, 40 g of pre-sleep casein raised overnight whole-body and muscle protein synthesis by roughly 22% versus placebo (PMID 22330017), and a 12-week double-blind trial found greater gains in thigh muscle size and strength in the casein group (PMID 25926415). A 2021 systematic review concluded pre-sleep casein reliably stimulates overnight synthesis in young adults (PMID 32811763).
The warning, and the ceiling at B rather than higher, reflects a key limitation: casein is not uniquely superior. A double-blind trial directly comparing casein with whey found no difference between them (p>0.44; PMID 36857005), so the benefit appears to come from eating protein before sleep, not from casein specifically. Several trials were small, acute, or industry-funded, and a 2025 open-label soccer study (PMID 41470882) reported implausibly large effects and was rated low quality.
Regulators treat casein only as a food, not a recovery aid. The US FDA lists it as GRAS for food-safety purposes with no efficacy claim, and WHO/Codex cite casein as the gold-standard reference for protein quality (PDCAAS 1.0), not as proof it speeds recovery. Evidence in older and non-resistance-trained people remains thin.
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 = 0.679
- 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 — Tier 條件達標，未降階
- detect_disputes — 偵測到 0 個 hard + 1 個 soft dispute
- decide_status — 依 tier + dispute 結果決定 status