Is Casein Protein Safe?

Casein is the predominant protein in milk.

Casein is the predominant protein in milk.

Casein is the predominant protein in milk, commonly used as a nutritional supplement. The amino acids, or protein building blocks, in casein can help support muscle growth and other physiological functions either as a substitute for or in addition to whole-food protein sources. Casein is a high-quality protein that can benefit your health; however, it may also have the potential to cause unwanted side effects.


Casein makes up between 70 and 80 percent of the protein in cow’s milk, according to a report in the September 2004 issue of the “Journal of Sports Science and Medicine.” It is isolated from milk using either an enzyme or an acid solution to precipitate the protein. The precipitated casein is then washed and dried, and at that point, it is ready to be incorporated into protein supplements. The process results in a product that contains not only casein but also additional milk components such as calcium and phosphorus.


As a protein containing all of the essential amino acids -- those that you must consume through your diet -- casein can help you to avoid a deficiency of any of the amino acids you need for optimal health. It is a highly digestible protein. Because the casein you consume releases its amino acids into your bloodstream in a slow and controlled manner, it allows a steady influx of nutrients into your system. Isolated casein contains almost no lactose, making it a safe milk product to consume if you are lactose intolerant.


Despite its benefits, casein can also be unsafe for consumption. If you suffer from a milk allergy, this protein can aggravate your symptoms. Other safety issues concern high protein intake in general and are not necessarily related specifically to casein; however, including concentrated levels of casein supplements in your diet can negatively impact your health. A high-protein diet may cause calcium to leach from your bones. In the presence of kidney disease, a high-protein diet can stress your kidneys.


Preliminary studies suggest that casein consumption, either alone or as a component of milk products, may potentially play a role in increasing the risk of Type 1 diabetes, autism and prostate cancer, according to the University of Michigan Health System. However, no substantiated or clear link exists between casein and these disorders.

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About the Author

A writer since 1985, Jan Annigan is published in "Plant Physiology," "Proceedings of the National Academy of Sciences," "Journal of Biological Chemistry" and on various websites. She holds a sports medicine and human performance certificate from the University of Washington, as well as a Bachelor of Science in animal sciences from Purdue University.

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