Caseins are proteins in milk containing amino acids, which are important for growth and development, especially of young nursing children and animals.
The key reasons why cow milk is such an important human food is that the milk contains casein.
Caseins are highly digestible in the intestine and are a high quality source of amino acids.
Most whey proteins are not as easily digested in the intestine as are casein proteins, but all of the whey proteins do digest to some degree. A person with a milk protein allergy has more difficulty in digesting whey proteins. Thus, the amount of undigested whey protein in the intestine would be large enough to trigger an immune system response.
The whey protein most often responsible for milk protein allergy is ß-lactoglobulin.
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