Humans depends on milk of cow mostly when we compare with that other being in early 19th century some of the researchers has found that some substance in milk which is from cow is causing problems to the human beings later in the end of 19th century some other analyst has found that milk is of various categories among them some commonly A1 and A2 is observed and they are mostly consumed by humans. When milk is consumed it goes into the stomach and there it breaks into fragments of proteins and amino acids they are absorbed into the intestine . when we compare difference between A1 and A2 variants of milk the position of amino acids in their chain, In case of A1 67 th place there will be histidine and in case of A2 proline will be where as humans and A2 milk will be almost same and they don’t show any changes whereas A1 milk is taken into account they gets converted into the BCM-7 which is a very potent substance.

Effects of the A1 & A2 milk in human actually this study has been conducted in rabbits where the A1 milk has fed to some rabbits and A2 milk is given to some group of rabbits later reports has shown that the rabbits which have been fed with the A1 milk have shown fatty contents on the walls of blood vessels which may progress and causes severe cardiac problems like angina and etc. Whereas the A2 milk has does not shows such effects. A1 milk also has the potentiality to increase the number of low-density lipoproteins and to decrease the number high-density lipoproteins which is referred as the good cholesterol. Fatty traces are made up of foam cells while in the case of normal atherosclerosis develop from macrophages that have taken up ox-LDL.  In a damaged vessel. The devouring of beta casein leads to aggravation of symptoms related to the autism and schizophrenia. But These effects were imputed by the opioid activity of BCM-7 and to oxidative stress, that leads to the neurological deficits that materialize as symptoms of autism and schizophrenia.

The European Food Safety Authority reviewed some scientific literature based on the BMC-7 concept and published a review article in 2009 saying about the variations in milk and problems in it. Even through BCM-7 contains some useful effects but less Actually, this problem has been occurred due to the mutation in the cow before thousands of years ago and cattle has been taken to western countries where the proline is replaced with histidine at position 67, spreading widely throughout the herds of the western world through breeding till now. Whereas the Asian especially in subcontinental countries like India are with A2 milk producing breeds till 18th century only a few amounts of cows in India used to produce A1,but this has been changed in this century it may be due to increase the demand for milk in India, many of the herdsmen has shown interest in A1 milk producing breed cows like jersey, Karan swiss, Holstein breed cows especially this breed cows do produce more amount of milk when compare with that of A2 breed cows which happened with the help of White Revolution it introduced foreign cow breeds to India which are capable of producing bulk amount of milk and replaced the Indian cow. In New Zealand and Australia now they started finding a solution to these problems by pushing the people to drink the A2 milk which may be a high cost for them.

source: http://www.ijamscr.com/sites/default/files/articles/IJAMSCR-17-124-163-167.pdf