Supplement

Casein Protein

Casein protein

Evidence TierBWADA NOT PROHIBITED

tuneTypical Dose

Common pre-sleep casein range

watchEffect Window

Acute overnight MPS effects are immediate.

check_circleCompliance

WADA NOT PROHIBITED

Overview

Clinical Summary

Casein is a practical slow-digesting protein, especially for pre-sleep use, but it is not clearly superior to other quality proteins for long-term muscle gain.

Casein’s clearest unique role is pre-sleep protein feeding because it digests more slowly and can support overnight amino acid availability. That supports overnight muscle-protein synthesis. The stronger version of the claim, that casein is clearly superior for long-term hypertrophy, is not well established. It is mainly a practical protein-timing option.

Casein digests more slowly than whey, helping sustain amino acid availability over several hours and making it useful in overnight feeding contexts.

Outcomes

What This Is Expected To Influence

Primary Outcomes

  • Increased overnight muscle protein synthesis in pre-sleep use

Secondary Outcomes

  • Practical protein-timing option

Safety

Contraindications and Interactions

Contraindications

  • Milk protein allergy

Side effects

  • GI discomfort

Interactions

No entries provided

Avoid if

  • You have dairy allergy or significant dairy intolerance

Evidence

Study-level References

cas-SRC-001Randomized controlled trial
Sourceopen_in_new

Trommelen J, et al. Protein Ingestion before Sleep Increases Overnight Muscle Protein Synthesis Rates in Healthy Older Men: A Randomized Controlled Trial. Am J Clin Nutr. 2018;108(5):1009-1017. doi:10.3945/ajcn.117.161570. PMID:28855419.

Population: Healthy older men.

Dose protocol: 20 to 40 g casein before sleep

Key findings: Increased overnight muscle protein synthesis.

Notes: Best direct RCT.

Paper content

This is the cleanest direct casein trial for pre-sleep use. It supports overnight muscle protein synthesis rather than unique long-term hypertrophy superiority.

cas-SRC-002Systematic review
Sourceopen_in_new

Snijders T, et al. Effects of pre-sleep protein consumption on muscle-related outcomes: A systematic review. Eur J Sport Sci. 2020;20(9):1180-1192. doi:10.1080/17461391.2020.1793440. PMID:32811763.

Population: Young and older adults in pre-sleep protein studies.

Dose protocol: Various pre-sleep protein protocols

Key findings: Acute MPS support with less certain long-term superiority.

Notes: Best overview.

Paper content

This review is useful because it narrows the casein story. Acute overnight MPS is supported, but long-term superiority claims are much weaker.

cas-SRC-003Randomized controlled trial.
Sourceopen_in_new

Bayrakdaroglu S, Ates ZH, Ceylan HI, Kul M, Muntean RI, Dhahbi W. Casein Supplementation Timing and Exercise Performance in Soccer Players: Pre-Sleep vs. Post-Exercise Intake-A Randomized Controlled Trial. Nutrients. 2025;17(24):3938. doi:10.3390/nu17243938. PMID:41470882.

Population: Highly trained male soccer players.

Dose protocol: 30 g micellar casein pre-sleep or post-exercise vs control (n=24)

Key findings: Both timing conditions improved anaerobic performance. Pre-sleep improved jump height and mean power. Post-exercise improved peak power and fatigue index.

Notes: Small sample in trained athletes. Supports casein's performance utility beyond MPS.

Paper content

This RCT compared pre-sleep versus post-exercise casein supplementation (30 g micellar casein) in 24 trained male soccer players across three groups. Both timing conditions enhanced anaerobic performance metrics compared to control. Pre-sleep intake improved countermovement jump height and mean power, while post-exercise intake improved peak power and fatigue index. Neither timing strategy was clearly superior to the other. The study supports the practical value of casein supplementation for athletic performance but does not establish an optimal timing window.

cas-SRC-004Randomized controlled trial.
Sourceopen_in_new

Trommelen J, van Lieshout GAA, Pabla P, et al. Pre-sleep Protein Ingestion Increases Mitochondrial Protein Synthesis Rates During Overnight Recovery from Endurance Exercise: A Randomized Controlled Trial. Sports Med. 2023;53(7):1445-1455. doi:10.1007/s40279-023-01822-3. PMID:36857005.

Population: Healthy young men.

Dose protocol: 45 g casein (or whey) before sleep after evening endurance exercise (n=36)

Key findings: Pre-sleep casein increased mitochondrial and myofibrillar protein synthesis overnight. No difference between casein and whey.

Notes: Extends pre-sleep casein evidence from resistance to endurance exercise. Well-designed acute study.

Paper content

This RCT tested whether pre-sleep protein (45 g casein or 45 g whey) could enhance overnight muscle protein synthesis after evening endurance exercise in 36 healthy young men. Pooled protein ingestion resulted in greater mitochondrial and myofibrillar protein synthesis rates compared to placebo. Casein and whey produced equivalent results. The study extends the pre-sleep protein literature from resistance exercise to endurance exercise recovery and confirms that casein supports overnight protein synthesis in this context, though it does not show superiority over whey for this specific application.

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