Discover the differences between A1 and A2 milk proteins, their potential health impacts, and the variation in cow breeds. While some studies suggest A2 milk may be healthier, conclusive evidence is lacking. This article highlights key differences to help consumers choose.
A1 milk releases a compound called β-casomorphin-7, which is held responsible for adverse health outcomes, including inflammation and gastrointestinal discomfort.
Different cow breeds produce varying proportions of A1 and A2 milk. For example, Charolais, Guernsey, Jersey, and Limousin have higher proportions of A2 milk.
While some studies link A1 milk to health issues like type 1 diabetes and gastrointestinal problems, conclusive evidence is lacking.
Sheep, buffalo, goat, and European-type cattle milk are A1 milk-free options.
What is A1 and A2 milk?
Milk is a good source of protein. The main protein of cow's milk is casein, constituting 80% of the total protein. Casein variants include beta-casein (β-casein), about 40% of the total casein found in cow's milk. β-casein has 13 genetic variations found in cow's milk, including:
- A1 milk. A1's β-casein chemical structure differs from A2 milk by one amino acid. The difference in chemical structure causes A1 β-casein to release a compound called beta casomorphin-7 (BCM-7) when exposed to digestive enzymes. The compound is suspected to cause inflammation and gastrointestinal discomfort.
- A2 milk. A2 β-casein was initially identified in cow's milk. However, A1 β-casein mutated from A2 β-casein — and it's been more prevalent in cow's milk since.
Different breeds produce different percentages of A1 and A2 β-casein. For instance, Charolais, Guernsey, Jersey, and Limousin cows primarily produce a higher proportion of A2 milk compared to Holstein Friesian, another internationally bred dairy cow. For example, only one-third of Holstein Friesian cows produce A2 milk — the remaining produce a mix of A1 and A2 milk or only A1 milk.
Does A1 milk cause disease?
Some studies suggest that A2 milk is healthier than A1. For instance, A1 milk has been claimed to affect health adversely by causing several diseases. Let's take a look at what the research says:
Type 1 diabetes
Type 1 diabetes is an autoimmune disorder that is a common chronic childhood disease. Since type 1 diabetes has increased in children, environmental factors such as nutrition have gotten the attention of researchers.
In type 1 diabetes, the body misdiagnoses its cells as foreign cells. As a result, misled immune cells attack insulin-secreting cells leading to organ dysfunction.
A1 milk has been on the radar due to its BCM-7 content. This is because researchers have hypothesized that BCM-7 activates autoantibodies. In the case of type 1 diabetes, BCM-7 may damage insulin-producing cells in genetically susceptible children.
In Scandinavia, the incidence of type 1 diabetes in children was higher than in Iceland. Researchers studied A1 and A2 milk consumption in those countries to determine whether the consumption of A1 or A2 milk contributes to disease incidence. Results showed that A1 milk consumption was significantly higher in Scandinavia than in Iceland. In addition, the consumption of A1 milk was positively correlated with type 1 diabetes incidence in 2-year-old children. The study concluded that lower consumption of A1 milk can be associated with a lower incidence of type 1 diabetes in Iceland than in Scandinavia.
Keep in mind that no conclusive evidence shows that A1 milk causes type 1 diabetes.
Coronary heart disease
Coronary heart disease (CHD) is a condition that develops when the blood vessels become damaged. This usually happens due to the buildup of deposits containing cholesterol and other substances in the arteries, known as atherosclerosis.
Some risk factors for developing coronary heart disease include obesity, impaired blood glucose metabolism, high blood pressure, and high cholesterol.
Some studies showed a correlation between ischemic heart disease mortality and A1 milk. For example, one study investigated the effects of A1 β-casein and A2 β-casein supplementation in individuals with a high risk of heart disease. However, the results revealed that consumption of neither A1 β-casein nor A2 β-casein has a disadvantage for cardiovascular disease.
Therefore, the results of studies don't provide enough evidence for the cause-and-effect relationship between heart disease and A1 milk.
A1 milk is thought to increase gastrointestinal problems. Studies showed a correlation between A1 milk consumption and gastrointestinal symptoms, including abdominal pain.
A systematic review examined the gastrointestinal effects of A1 β-casein and A2 β-casein. Researchers concluded a limited study on humans that showed A1 milk could cause delayed intestinal transit, changes in stool consistency, and digestive discomfort.
As a result, some people may have gastrointestinal issues after consuming A1 milk. In this case, A2 milk may benefit some people regarding digestive symptoms.
Sudden infant death
Sudden infant death is a common cause for under one-year-olds, and researchers hypothesize that BCM-7 may play a role. Therefore, some children may be more susceptible to the adverse effects of A1 milk.
A study has been proposed on the possible role of beta-casomorphin (beta-CM) in apnea, which may lead to sudden infant death. However, the evidence is inconclusive.
On the other hand, according to the European Food Safety Authorities (EFSA), no strong evidence shows the relationship between β-casomorphin-7 and chronic diseases such as diabetes and heart diseases. However, the report indicated that some people may experience gastrointestinal changes and disorders caused by A1 milk.
- If you prefer A2 milk, you can consume sheep, buffalo, or goat milk which are A1 milk-free options.
- In some countries, A1-free milk is commercially available; you can check your supermarkets to see if they sell A1-free milk.
- It can be helpful to know milk of European-type cattle does not contain A1 milk.
There is no conclusive evidence showing the superiority of A2 milk over A1. However, you should always consult your healthcare provider to inform them about your nutrition and health.
- European Journal of Clinical Nutrition. The A2 milk case: a critical review.
- Journal of Food Engineering and Technology. A1- and A2-Milk and Their Effect on Human Health.
- Annals of Nutrition and Metabolism. Lower Consumption of Cow Milk Protein A1 β-Casein at 2 Years of Age, Rather than Consumption among 11- to 14-Year-Old Adolescents, May Explain the Lower Incidence of Type 1 Diabetes in Iceland than in Scandinavia.
- British Journal of Nutrition. Effect of dietary supplementation with beta-casein A1 or A2 on markers of disease development in individuals at high risk of cardiovascular disease.
- Advances in Nutrition. Systematic Review of the Gastrointestinal Effects of A1 Compared with A2 β-Casein.