Milk is very common term for any human being. Since our childhood, we are drinking milk as one of the essential part of our diet. The classifications in layman term for milk are on the basis of source e.g. cow’s milk, buffalo’s milk, goat’s milk, camel’s milk, etc. With the advancement in food technology, the classification of milk took another side based on the fat percentage in milk e.g. full cream milk, toned milk, double toned milk, skimmed milk, standardised milk, etc. These are the most common classifications anyone knows.
But have you heard about A1 milk and A2 milk? What is this classification based on? Can you guess? Surely not on the basis of quality grade.
Then What???
Well, to understand this, we have to take a deep dive into the chemistry of milk. Milk contains two different types of proteins: whey protein and casein protein. Whey consist of only 20% portion of total protein whereas major portion, 80% is composed of casein. The casein proteins are further classified into four subtypes: αs1, αs2, β, and k casein. β-casein is one of the important casein subtype as it consist of 35-40% of total casein in milk. β-casein differs on the basis of genetic variations and it causes 13 different types of β-casein availability in cow’s milk. This β-casein variation is the reason behind A1 and A2 variety of milk. A1 β-casein (A1 milk) and A2 β-casein (A2 milk) varies from each other in one amino acid i.e. 67th amino acid in the chain. A1 contains histidine whereas A2 contains proline at this position. Due to this difference in amino acid, there is a huge variation in digestibility and impact of A1 milk and A2 milk on human health.
When the milk is ingested, various digestive enzymes starts working on it and breaks down the milk protein into small peptide chains. In A1 milk, due to the presence of histidine, the chain is broken down into a peptide of 7-amino acids which is called Beta-casomorphin-7 or BCM-7 whereas in A2 milk, this BCM-7 is not released due to absence of histidine at 67th position.
Since BCM-7 is a kind of morphin, has opioid like properties and linked with many human health related issues like type-1 diabetes, health diseases, autism, digestive issues, and infant death. Although sufficient in vivo research is not present about impact of BCM-7 in healthy adults but it has been found by many researchers that BCM-7 affects infants and adults with compromised digestive health (Celiac disease, stomach ulcers, etc.) predominantly. The reason behind this is the improper functioning of DPP(IV) i.e. dipeptidyl peptidase IV or high permeability of intestinal membrane which facilitates the release of BCM-7 in blood stream. Whereas in healthy adults, DPP(IV) enzyme breaks down the BCM-7 into BCM-5 or BCM-3 or furthermore to make it less adverse.
ICAR-NBAGR, Karnal conducted the study on Indian cow breeds to check the presence of A1 and A2 breed ratio. It has been found that 91% of cows had A2A2 alleles, 9% has heterogeneous A1A2 alleles whereas A1A1 alleles was found absent in Indian breeds. It was further researched that India has high milk contribution from buffalos as well that produce A2-type milk, henceforth the chances of consumption of A1 milk by Indians has reduced to 0.24g/day which is 5-10 times lesser than western countries surveyed.
As we know India is the world largest producer of milk as well as consumer of milk. If the milk is converted to A1-type, one can imagine its health impact on wide population.
So the question is, how can it be stopped?
National Academy of Agricultural Sciences has published a report on A1 and A2 milk and has recommended to avoid the cross-breeding of cows with bulls having A1 alleles. This has been found in researches that thousands of years ago, A1 alleles carrying bulls were found genetically superior for higher yield and henceforth chosen for crossbreeding programme. Unconsciously it caused mutations in cows and converted them to produce A1 milk.
Moreover, World Health Organisation (WHO) recommends to provide mother’s milk to infants for 6 months at least, continued to 2 years further. It creates healthy digestive system in infants and prevent them from milk-protein intolerances.
Despite of all these studies, there is still lack of in vivo research about A1 milk impact on humans. Majority of research has been conducted on laboratory animals and its exact effects on humans are still debatable. The A1 alleles hypothesis is very crucial for human health if it’s proven correct in in vivo studies however, research finding are not sufficient to prove it presently. Precautions are the only measures that can be adopted while crossbreeding native breeds until the research finding on A1 milk impact is proven.
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