New FAQ added
We added a FAQ about A1 beta casein. Overall, there's some preclinical research suggesting that A1 beta casein may be associated with certain diseases, but human evidence is lacking.
Casein is a type of protein found in milk, and it makes up around 80% of the proteins in cow’s milk. Casein is sometimes called a slow-digesting protein because it forms a gel in the stomach and therefore takes longer to digest than whey protein.
Casein is most often used for
Last Updated:June 4, 2024
Casein is a group of phosphoproteins that is found in milk and milk-based products. When a coagulant is added to milk, it separates into curds (the casein) and whey. Casein is most often supplemented in the form of a dry powder. The most common supplement forms of casein are micellar casein and casein hydrolysate. Micellar casein is most commonly used, and this form is digested very slowly. Casein hydrolysate is a predigested form of casein and will be absorbed more quickly.
Casein offers the same benefits as any other protein supplement — an easy way to increase your protein intake. The benefits of a higher protein intake include limiting muscle loss during periods of caloric restriction, slowing down muscle loss due to aging (sarcopenia), and supporting muscle growth with resistance training.
Casein contains all the essential amino acids. It also contains leucine (although less leucine than whey protein) which helps stimulate muscle protein synthesis (MPS).[3] Casein ingestion will result in a slow release of amino acids into the bloodstream. This can be useful as a nighttime drink to ensure ongoing MPS while asleep. Following casein intake, the amino acid concentration slowly rises, peaking at about 7 hours post intake (compared to whey protein which peaks at 1-3 hours).[4]
Casein may also increase satiety, helping you to stay fuller for longer compared to other types of protein, since it is slower to digest. This effect is not universal[5] but is especially noted in the long term when casein is used regularly over a period of weeks.[6]
Other possible benefits — including lowering glucose in diabetics, lowering blood pressure, and lowering lipids — remain uncertain.[7] Casein also does not have any direct benefit in terms of fat loss, although it might help with satiety.[8]
Casein supplementation is safe for most people. It is a dairy product, so people who do not tolerate dairy may experience mild gastrointestinal side effects, especially bloating and flatulence, when using casein. These symptoms could point to being intolerant to casein proteins themselves, or they could indicate lactose intolerance.[9]
A casein allergy is also possible. This is an inappropriate immune reaction to the proteins in casein.[10] Although avoiding casein would be prudent in the case of casein intolerance or allergy, an allergic reaction is more severe and can be life-threatening.
Once ingested, casein coagulates (curdles) in the acidic environment of the stomach, which is why it is digested slowly. It moves into the intestine and is broken down into amino acids that can be used to initiate and maintain the process of muscle protein synthesis. This process takes several hours, with amino acid concentrations reaching their peak around 7 hours after ingestion.[6]
Casein supplements can be used as a part of your daily protein intake. You can use our protein intake calculator to work out your own optimal daily protein intake.
While the RDA for protein is 0.8 grams of protein per kilogram of body mass per day (g/kg/day), most people would benefit from having a higher protein intake in the range of 1.2g/kg/day to 1.6g/kg/day. Older people, athletes, and highly active people could need up to 2g/kg/day.[1][2]
New FAQ added
We added a FAQ about A1 beta casein. Overall, there's some preclinical research suggesting that A1 beta casein may be associated with certain diseases, but human evidence is lacking.
Full FAQ and database update
The casein page was update to include more specific and detailed FAQs. Additional research was reviewed regarding casein as a protein supplement, especially its use as a pre-sleep protein bolus. Finally, we added data from 2 recent meta-analyses to the database.