How it works
Casein makes up about 80% of milk protein. In the acidic stomach it forms a gel, which slows digestion and produces a smaller but longer-lasting rise in blood amino acids than whey. This steady release suits long gaps without food, such as overnight. Studies show protein eaten before sleep is digested and absorbed overnight and built into muscle. Longer training studies suggest pre-sleep protein may add to strength and muscle gains, though total daily protein still matters most.
What research supports
- Provides a sustained release of amino acids over several hours
- Pre-sleep intake (about 30–40 g) increases overnight muscle protein synthesis in studies
- Helps meet daily protein targets and may increase fullness
- Supports muscle gains with resistance training as part of adequate total protein intake
Dosage
Typical research dose: 30–40 g of casein about 30–60 minutes before sleep, or 0.25–0.4 g/kg per serving at other times, within a total daily intake of around 1.6–2.2 g/kg for muscle gain.
Timing
Casein is most often used before bed or when a long gap between meals is expected. It can also be used at any time to reach daily protein targets. Mixed with less liquid, micellar casein becomes thick enough to eat like a pudding.
Side effects
- Bloating or digestive discomfort in some people, especially in large doses
- Symptoms in people with lactose intolerance, depending on the product
Cautions
- Avoid if you have a cow's milk protein allergy
- People with kidney disease should discuss protein intake with a doctor
- Adds calories before bed; account for it in daily intake if managing weight
- Athletes subject to anti-doping rules should only use products certified by an independent third-party testing program for banned substances; certification lowers, but does not eliminate, the risk of contamination.
Food sources
Cottage cheese, Greek yogurt and skyr, Milk, Quark, Hard cheeses.