Some athletes say that using casein protein improves weight training results by providing a steady supply of amino acids over several hours.
What Do the Advocates Say?*
Protein is necessary for building and repairing muscle, and this is especially important for bodybuilders. All types of protein, including casein, provide the body with amino acids. However, compared with other protein supplements, casein is slowly digested, resulting in a slower yet more prolonged rise in blood levels of amino acids, so some fitness professionals believe it may help support muscle growth and strength gains in weight-training programs.
How Much Is Usually Taken by Athletes?
In a controlled trial,1 1.5 grams per day of predigested casein protein per 2.2 lbs body weight helped overweight men gain strength and lean body mass, and lose body fat during a weight loss diet and weight training program. These changes were greater than for men using a similar amount of whey protein along with the same diet and exercise plan.
People who are allergic to dairy products could react to casein protein and so should avoid it. Predigested casein protein may cause fewer reactions in people with dairy allergies, but may nonetheless cause reactions in some.2
Some, though not all, preliminary research has suggested that diets high in milk products, and therefore high in casein, might be associated with increased risk of type 1 diabetes and heart disease.3, 4 One type of casein protein has been suggested as the possible contributor to these diseases,5, 6 but other milk proteins have also been implicated in type 1 diabetes,7 and other components of dairy products, such as saturated fat and cholesterol are known to increase heart disease risk.8, 9, 10 At this time, whether casein protein plays a role in the causation of type 1 diabetes or heart disease is unclear and requires more research.
Animal and preliminary human research has also suggested that some types of casein protein might be associated with increased risk or severity of autism.11 Uncontrolled trials have suggested that eliminating sources of casein as well as gluten or other proteins may reduce symptoms of autism to some degree.12 Controlled studies have also reported promising results,13, 14 but have been criticized,15 and a double-blind trial found no effect of a casein- and gluten-free diet on autism symptoms.16 More research is needed to further explore any potential link between casein protein and autism.
Animal research has suggested that a diet high in casein protein (but not a diet with similar amounts of plant proteins) might increase cancer risk.17, 18, 19 No human research has specifically studied casein protein as a potential cancer risk. Preliminary human studies of dairy foods, which are high in casein, find little association between high dairy consumption and cancer risk. For example, milk consumption may be associated with small increases in prostate cancer risk,20 and small decreases in colorectal cancer risk,21 but no change in risk for other cancers.22 More research is needed to determine whether regular use of casein protein supplements affects cancer risk.
As with protein in general, long-term, excessive intake of casein protein may be associated with deteriorating kidney function and possibly osteoporosis. However, neither kidney nor bone problems have been directly associated with casein consumption, and the other dietary sources of protein typically contribute more protein to the diet than does casein.
Interactions with Supplements, Foods, & Other Compounds
At the time of writing, there were no well-known supplement or food interactions with this supplement.
Interactions with Medicines
As of the last update, no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
Where to Find It
Milk protein is 70 to 80% casein, so milk, yogurt, cheese and other dairy products are high in casein. Nondairy foods sometimes contain added casein as a whitening or thickening agent. Casein is also used in some protein supplements.
*Athletes and fitness advocates may claim benefits for this supplement based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles.
1. Demling RH, DeSanti L. Effect of a hypocaloric diet, increased protein intake and resistance training on lean mass gains and fat mass loss in overweight police officers. Ann Nutr Metab 2000;44:21-9.
2. Wal JM. Cow’s milk proteins/allergens. Ann Allergy Asthma Immunol 2002;89(6 Suppl 1):3-10.
3. Truswell AS. The A2 milk case: a critical review. Eur J Clin Nutr 2005;59:623-31 [review].
4. German JB, Gibson RA, Krauss RM, et al. A reappraisal of the impact of dairy foods and milk fat on cardiovascular disease risk. Eur J Nutr 2009;48:191-203 [review].
5. Elliott RB, Harris DP, Hill JP, et al. Type I (insulin-dependent) diabetes mellitus and cow milk: casein variant consumption. Diabetologia 1999;42:292–6.
6. McLachlan CNS: b-casein A1, ischaemic heart disease mortality, and other illnesses. Med Hypotheses 2001;56;262–72 [review].
7. Martin JM, Trink B, Daneman D, et al. Milk proteins in the etiology of insulin-dependent diabetes mellitus (IDDM). Ann Med 1991;23:447-52 [review].
8. Tholstrup T. Dairy products and cardiovascular disease. Curr Opin Lipidol 2006;17:1-10.
9. Sun Z, Cade JR. A peptide found in schizophrenia and autism causes behavior changes in rats. Autism 1999:3;85–95.
10. Kamiński S, Cieslińska A, Kostyra E. Polymorphism of bovine beta-casein and its potential effect on human health. J Appl Genet 2007;48:189-98.
11. Sun, Z, Cade JR, Fregly M, Privette RM. β-casomorphin induces Fos-like immunoreactivity in discrete brain regions relevant to schizophrenia and autism. Autism 1999:3:67–83.
12. Christison GW, Ivany K. Elimination diets in autism spectrum disorders: any wheat amidst the chaff? J Dev Behav Pediatr 2006;27:S162-71 [review].
13. Knivsberg, A-M, Reichelt, KL, Høien, T, Nødland, M. Effect of dietary intervention on autistic behavior. Focus on Autism and Other Developmental Disablities 2003;18:247-56.
14. Whiteley P, Haracopos D, Knivsberg AM, et al. The ScanBrit randomised, controlled, single-blind study of a gluten- and casein-free dietary intervention for children with autism spectrum disorders. Nutr Neurosci 2010;13:87-100.
15. Millward C, Ferriter M, Calver S, Connell-Jones G. Gluten- and casein-free diets for autistic spectrum disorder. Cochrane Database Syst Rev 2008;2:CD003498 [review].
16. Elder JH, Shanker M, Shuster J, et al. The gluten-free, casein-free diet in autism: Results of a preliminary double blind clinical trial. J Autism Developmental Disorders 2006;36:413-20.
17. Campbell TC. Dietary protein, growth factors, and cancer. Am J Clin Nutr 2007;85:1667 [letter].
18. Youngman LD, Campbell TC. The sustained development of preneoplastic lesions depends on high protein intake. Nutr Cancer 1992;18:131-42.
19. Youngman LD, Campbell TC. The sustained development of preneoplastic lesions depends on high protein intake. Nutr Cancer 1992;18:131-42.