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| What to consume: A1 milk or A2 milk? | | | Dr. Wahied Khawar Balwan | 7/3/2021 11:58:27 PM |
| Milk is one of the most nutritious foods for human and is consumed right from the birth and almost throughout the life as such or in the form of milk products. Milk is highly nutritious providing an important source of high quality proteins, carbohydrates and micronutrients and is considered as almost complete food. Dairy cow milk is considered as nutritionally superior over other species. Nutritionally cow milk is about 87 % water, 4.6% lactose sugar, 3.7% triglycerides, 2.8% milk protein, 0.54% minerals and 3.36% other constituents. Milk protein constitutes of 36% b-casein, 27% ?-Casein, 9% ?-casein and 27% peptides and amino acids. Among the caseins, ?casein is the second most abundant protein, constitutes roughly 2.5 grams per glass of the cow milk. There are two types of milk available in market A1 and A2. A1 milk is produced by European cow breeds (Holstein, Jersey etc.), while Indian cow (Desi cow) is source of A2 milk. World consumers are paying more attention on this topic because of recent correlation between A1 b-casein intake and the incidence of certain non-communicable diseases. This boosted A2 milk sales and prompted the New Zealand Food Safety Authority and European Food Safety Authority to propose rigorous analysis of A1 milk health claims.
A1 AND A2 TYPE MILK
b-casein is 209 amino acids long peptide and amino acid at position 67 differentiates A1 and A2 milk. A1 milk has histidine at position 67 of b-casein 4 while A2 milk has proline at the same position. Thus, milk having b-casein with proline at position 67 is referred as A2 type milk while milk having b-casein with histidine at position 67 is A1 type milk.
EVOLUTION OF A1 MILK FROM A2 MILK
Originally all cow milk was of the A2 type but during evolutionary process, genetic mutation affected some European cattle (Jersey, Guernsey, Holstein Friesian) in b-case in gene, probably 5000- 10,000 years ago. This mutation led to genetic variants of b-casein and out of these, A1 and A2 are the most common. The gene at position 67 encoding amino acid proline mutated during evolution and started encoding histidine. The frequency of A1 allele was increased gradually in the population during selection of animals for higher milk production. While Indian cattle have evolved naturally without any selection pressure and have A2 allele of b-casein. However, with the onset of white revolution in India to increase the milk production, exotic breeds like Jersey, Guernsey, Holstein Friesian etc. were used for cross breeding or their semen was used for the purpose of artificial insemination. This increased the proportion of A1 allele in the population.
EFFECTS OFA1 MILK ON HEALTH
The bovine ?-casein variants for A1 and A2 milk differ in amino acid at position 67 with histidine and proline, respectively. This leads to key conformational changes in the secondary structure of ?-casein protein and their susceptibility to the gastrointestinal proteolytic digestion. Presence of histidine in A1 milk and proline in A2 milk at position 67 in the ?-casein of milk, results in different products on proteolytic digestion. Gastrointestinal digestion of A1 ?-casein releases bovine betacasomorphin-7 (BCM-7), while A2 ?-casein digestion releases bovine beta-casomorphin-9 (BCM-9). BCM-7 is a strong opioid and has affinity for the mu opioid receptors. Generally, opioids are group of substances that act on opioid receptors to produce morphine-like effects. BCM-7 is devil as it can potentially affect mu opioid receptors present in the gastrointestinal, nervous, endocrine and immune system. It is also known to be an oxidant of low dietary lipoproteins (LDL) and oxidation of LDL is believed to be important in formation of arterial plaque. Hence generation of BCM-7 is considered to be the major causative factor responsible for many A1 milk related health disorders like type1 diabetes, autism, coronary heart disease, arteriosclerosis, sudden infant death syndrome etc. However, A2 ? casein, which yields BCM-9 on digestion, has not been linked to such type of illnesses.
TYPE-1 DIABETES
Epidemiological evidences claim that consumption of A1 milk is associated as a risk factor for type1 diabetes. Animal trials have supported the linking of type1 diabetes to milk exposure in general and A1 ?-casein in particular. Type1 diabetes is typically diagnosed in children, and is characterized by lack of insulin in the body. Scientific studies have concluded that risk of type1 diabetes is higher among children consuming A1 milk during childhood. Animal studies have provided conflicting results whereas, some workers have found no difference between A1 and A2 ?-casein milk consumption and Type I diabetes. Others have shown the adverse effects of A1 ?-casein on type1 diabetes. Studies at global level demonstrates that incidence of Type1 diabetes is higher in the people consuming A1 ?casein. However, no clinical trials on humans have been carried out to study the effect of A1 ?-casein on type1 diabetes.
HEART DISEASE
Consumption of A1 milk also leads to higher incidence of heart diseases on long term basis. Various studies have linked the consumption of A1 milk with an increased risk of heart disease. Experimental trials on rabbits showed that consuming A1 ?-casein promoted fat deposition in blood vessels. The fat deposition was far much lower when the rabbit food was supplemented with A2 ?-casein. Accumulation of fat potentially clogs blood vessels and causes heart diseases. BCM-7 is known to possess oxidant property that leads to the oxidation of LDL. It is believed to be important in the formation of arterial plaque. Rabbits fed A1 ?casein developed more plaque in their aorta than rabbits fed A2 ?-casein. Some researchers support the hypothesis that consumption of A1 milk risk of heart diseases, but many studies have not linked higher rates of heart diseases with consumption of more milk.
SUDDEN INFANT DEATH SYNDROME
Sudden infant death syndrome (SIDS) is one of the most common cause of mortality among infants and is defined as unexpected death of an infant, without an apparent cause. Various studies have reported that infants who temporarily stopped breathing during sleep(known as sleep apnea and is linked to SIDS),had higher level of BCM-7 in their blood and urine, which indicates that some children might be sensitive to A1 ?-casein found in cow's milk.
AUTISM AND SCHIZOPHRENIA
Autism is a type of neurological condition in which patient suffers from poor social interaction and repetitive behavior. Theoretically, peptides like BCM-7 might play a role in the development of autism. It has been reported that drinking cow milk worsen behavioral symptoms in autistic children. Infants fed A1 milk, in comparison to breastfed infants, retained higher levels of BCM-7 and it was strongly associated with an impaired ability to plan and perform actions. Many studies on autistic and schizophrenic patients indicate that they excrete larger quantities of BCM-7 in their urine. However, the only known source of BCM-7 peptide is ?-casein.
DIGESTIVE DISORDERS
Cow milk is considered to be common cause of digestive discomfort (i.e. flatulence, bloating, abdominal distension etc.) possibly due to lactose intolerance among people. Receptors for muopioid peptides are expressed widely throughout the gastrointestinal tract. BCM-7 bioactive peptides released on the digestion of A1 ?-casein interact with mu opioid receptors and lead to intestinal inflammation, interferes with colonic microbiota and ultimately affects the stool composition. A study on rodents concluded that A1 milk consumption resulted in delayed gastrointestinal transit time as compared to A2 milk.
INFLAMMATORY PROBLEMS
The intake of A1 milk casein causes inflammatory responses which leads to lymphatic congestion and metabolic suppression. National Dairy Research Institute reported that mice fed on A1 ?-casein produced far more inflammatory compounds linked to heart diseases, eczema and asthma in comparison to mice fed A2 ?-casein. A1 milk worsens acne, eczema, upper respiratory infections, asthma and allergies. Ear infections, bronchitis and tonsillitis are also driven by A1 ?casein. A1 milk casein causes endometriosis (a condition in which the cells from the inner lining of uterus flourish outside the uterus) due to its inflammatory and immune-disruptive effect. Thus women consuming A1 milk may suffer from endometriosis and other reproductive complications.
CONCLUSION
The controversy about the health benefits of A1 and A2 milk cannot be solved until we have comprehensive research on this matter. The hypothesis 'A1/A2 milk and its impact on human health' is potentially very important for public health if proven. But we can still conclude that we should start changing our dairy herds to A2 milk producing cows. However, more research is required to prove the reality of the hypothesis of A1 and A2 milk. But as far as public health is concerned, we should not wait for A1/A2 hypothesis to be proven correct. Consuming A2 milk as precautionary measure will protect us atleast from A1 milk born disorders. By consuming A2 milk, one is no longer exposed to BCM-7 which is considered to be responsible for increased risk of type 1 diabetes, autism, digestive disorders, schizophrenia, SIDS etc. Hence role of government shall be decisive and support is indispensable to sort out anomalies regarding milk quality and standards for the betterment of human health.
'Any error in this manuscript is silent testimony of the fact that it was a human effort' |
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