Casein Protein

Micellar casein · Casein supplementation

Snapshot

Indications	Contraindications
Pre-sleep protein timing^1–5 Soccer aerobic capacity, with casein⁶ Endurance recovery markers⁷ Functional gut symptoms⁸	Milk allergy⁹ Soy allergy (some blends)¹⁰

Casein is the main protein in cow's milk, a slow-digesting amino acid source sold as micellar casein, caseinates, or hydrolysates. Supplementation is used to supply protein around resistance training and before sleep, where the timing is attributed to better muscle adaptation¹. Casein hydrolysate is also given with carbohydrate during multiday endurance racing, and partly hydrolysed milk casein is used where milk provokes functional gut symptoms.

Evidence for metabolic claims is weak. Pre-sleep casein showed limited to no effect on metabolism or appetite, and data are limited.¹ A systematic review found limited to no effect of pre-sleep casein on metabolism or appetite¹, and a crossover trial in women found no change in next-morning resting metabolic rate or appetite⁴. In soccer players, casein plus probiotics improved time to exhaustion over placebo, while casein alone did not differ significantly⁶. In mice, a 2021 feeding study found duckweed protein could replace part of dietary casein without changing growth or organ weights; no human trial has tested this. Products listing casein protein number in the tens of thousands, nearly all powders; see Form comparison.

The consequential caution is milk allergy, since casein is a milk derivative.⁹ Health Canada labels ask for a practitioner's advice before use in pregnancy, breastfeeding, or liver or kidney disease⁹.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

43 sources, 28 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources