Last Updated: March 20, 2024

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

What is casein?

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.

What are casein’s main benefits?

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]

What are casein’s main drawbacks?

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.

How does casein work?

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]

What are other names for Casein?
Note that Casein is also known as:
  • Casein
Casein should not be confused with:
Dosage information

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]

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Update History
2024-03-20 00:30:03

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.

  1. ^Stuart M Phillips, Stéphanie Chevalier, Heather J LeidyProtein "requirements" beyond the RDA: implications for optimizing healthAppl Physiol Nutr Metab.(2016 May)
  2. ^Jäger R, Kerksick CM, Campbell BI, Cribb PJ, Wells SD, Skwiat TM, Purpura M, Ziegenfuss TN, Ferrando AA, Arent SM, Smith-Ryan AE, Stout JR, Arciero PJ, Ormsbee MJ, Taylor LW, Wilborn CD, Kalman DS, Kreider RB, Willoughby DS, Hoffman JR, Krzykowski JL, Antonio JInternational Society of Sports Nutrition Position Stand: protein and exerciseJ Int Soc Sports Nutr.(2017 Jun 20)
  3. ^van Vliet S, Burd NA, van Loon LJThe Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein ConsumptionJ Nutr.(2015 Sep)
  4. ^Antonio J, Ellerbroek A, Peacock C, Silver TCasein Protein Supplementation in Trained Men and Women: Morning versus EveningInt J Exerc Sci.(2017 May 1)
  5. ^Justin Dela Cruz, David KahanPre-Sleep Casein Supplementation, Metabolism, and Appetite: A Systematic ReviewNutrients.(2021 May 30)
  6. ^Line Q Bendtsen, Janne K Lorenzen, Nathalie T Bendsen, Charlotte Rasmussen, Arne AstrupEffect of dairy proteins on appetite, energy expenditure, body weight, and composition: a review of the evidence from controlled clinical trialsAdv Nutr.(2013 Jul 1)
  7. ^McGregor RA, Poppitt SDMilk protein for improved metabolic health: a review of the evidence.Nutr Metab (Lond).(2013-Jul-03)
  8. ^Pal S, Radavelli-Bagatini S, Hagger M, Ellis VComparative effects of whey and casein proteins on satiety in overweight and obese individuals: a randomized controlled trial.Eur J Clin Nutr.(2014-Sep)
  9. ^Sebely Pal, Keith Woodford, Sonja Kukuljan, Suleen HoMilk Intolerance, Beta-Casein and LactoseNutrients.(2015 Aug 31)
  10. ^Wąsik M, Nazimek K, Nowak B, Askenase PW, Bryniarski KDelayed-Type Hypersensitivity Underlying Casein Allergy Is Suppressed by Extracellular Vesicles Carrying miRNA-150.Nutrients.(2019-Apr-23)
  11. ^Res PT, Groen B, Pennings B, Beelen M, Wallis GA, Gijsen AP, Senden JM, VAN Loon LJProtein ingestion before sleep improves postexercise overnight recoveryMed Sci Sports Exerc.(2012 Aug)
  12. ^Kim JPre-sleep casein protein ingestion: new paradigm in post-exercise recovery nutrition.Phys Act Nutr.(2020-Jun-30)
  13. ^Steininger K, Wodick RE, Späte WChondropathia patellae--study of the femoropatellar joints of healthy, athletic children.Sportverletz Sportschaden.(1990-Jun)
Examine Database References
  1. Metabolic Rate - Justin Dela Cruz, David KahanPre-Sleep Casein Supplementation, Metabolism, and Appetite: A Systematic ReviewNutrients.(2021 May 30)