Food and Health, cilt.7, sa.2, ss.128-137, 2021 (Hakemli Dergi)
Milk is composed of water, proteins, lipids, lactose, vitamins, and minerals. More than 80% of
most mammals’ milk proteins are constituted by caseins. Casein is a group of proteins and they
are sub-divided into αs1-, αs2-, β- and κ-casein families. Among these casein families, β-casein is
the second most abundant protein. Different mutations in the cow milk β-casein gene led to 12
genetic variants and most common of these are genetic variants A1 and A2. The A1 and A2 variants differ only at amino acid position 67, which is histidine in A1 or proline in A2 milk. This
difference in amino acid sequence suggests a conformational change in the secondary structure of
the expressed β-casein. Milk that contains A1 β-casein and A2 β-casein are known as A1 milk and
A2 milk, respectively. A1 β-casein milk releases an amino acid bioactive peptide called beta-casomorphin-7 (βCM-7) in small intestine. Beta-casomorphin-7 released from A1 β-casein is responsible for many human disorders like type-1 diabetes, autism, schizophrenia, alzheimer’s disease
(AD), attention deficit hyperactivity disorder (ADHD), multiple sclerosis (MS) and heart diseases.