Source and Components

1.1. Source

Casein is a protein that is derived from the milk of many species; most human consumption of casein comes from bovine (cow) milk.

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Casein is the insoluble portion of the milk, whereas whey is the soluble portion; the amount of casein in standard milk protein is approximately 80%, and human milk is variable depending on time spent lactating.[1][2][3][4]

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1.2. Components

Casein protein, like all protein, is a source of dietary amino acids. As it is an animal source, it is complete in the sense that it contains all essential amino acids in adequate enough numbers for proper human functioning at the minimum level of protein intake recommended.

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Casein protein also contains various bioactive peptides. These peptides are partially digested in the stomach, and prior to being broken down into their constituent amino acids they are able to exert effects in the intestines (prior to absorption). These effects may be wide-reaching, and are discussed in the following bullets.

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Like other dairy sources, Casein may  help your dental health. Studies have shown that it has the potential to strengthen tooth enamel against acid erosion and damage with its calcium, phosphate and hydroxide content.

List of Peptides in Casein

2.1. AlphaS-1 Peptide

Casein contains various Bioactive peptides, which can be defined as sequences of amino acids that are contained in dietary proteins and are partially denatured in the stomach to reveal short sequences. These sequences can exert biological effects in the intestines prior to being digested, or maybe digested through a peptide transporter.

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When supplemented to humans, the AlphaS-1 peptide is known to produce an anxiolytic effect. Two doses of 200mg may be able to reduce the response to perceived stressors. The anxiolytic effect may also provide better sleep in those with high levels of stress.

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Similar to the c12 peptide, AlphaS-1 may also have an ability to induce ACE-inhibitor like effects and reduce blood pressure.

AlphaS-1 is also a peptide that is noted to cause allergies, and thus persons allergic to dairy may also be allergic to this peptide in supplemental form.

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2.2. c12 Peptide

When administered in the form of tablets, the c12 peptide is able to reduce blood pressure in pre-hypertensive subjects in one study.[20] This is due to the c12 peptide having the properties of an ACE inhibitor

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2.3. Glycomacropeptides

Glycomacropeptides can be found in the casein portion of whole milk products, but due to their water soluble nature they leave the casein portion during chymosin treatment at the beginning stages of processing.[22] They do tend to be associated with casein protein as they originate with kappa casein molecules, hence their inclusion in this Examine page. Unless otherwise added afterwards however, they are not a normal component of casein supplementations.

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2.5. Casoxins and Casomorphins

Casoxins and Casomorphins are peptides which are able to act on the opioid system, which is involved in the rate of digestion. The class of casomorphins are opioid agonists (activators) and the casoxins opioid antagonists.[23]

Casein seems to have a higher relative content of casomorphins to casoxins, which may explain the reduced transit speed after consumption (as activation of the opioid system reduces intestinal motility).[24]