Answers to frequently asked questions on A2 milk protein

1)    What proteins are found in cows’ milk and why are they important?

Cow’s milk is a very good source of protein (around 9% by weight), which is important for health at any age, and particularly to support healthy growth and development in infancy and childhood.

Casein and whey are the two main forms of protein in cow’s milk.  Casein is around 4/5 of the total protein in cow’s milk, and whey makes up the rest.¹

Proteins are vital to the structure of all our body’s tissues. They also help to create and regulate chemical reactions, and act as messengers, so that our cells, tissues and organs can function normally. 

This is why dietary protein is important at any age for both physical and mental health, but particularly for growing babies and young children.

Unlike many plant-derived proteins, the milk proteins casein and whey both contain all the essential amino acids (building blocks of protein) that we need but can’t make for ourselves.

These milk proteins - and substances we make from them - also have benefits for heart health, energy metabolism, dental health and immune regulation, including prevention of some cancers.^1–3

These positive effects of the proteins in cow’s milk, along with the vitamins and essential minerals that it contains (particularly calcium, but also iodine, for which milk is a major dietary source) explain why milk is recommended as part of any healthy diet.⁴ 

Individuals who exclude milk and dairy products from their diets – including vegans and/or individuals with allergies and intolerances therefore need to make sure that their diet is carefully planned and/or supplemented to include adequate intakes of all the essential nutrients that milk and dairy products would provide.

2)    What is A2 milk protein?

A2 milk protein refers to a particular form of ‘beta-casein’, one of the major casein proteins found in cow’s milk.

Milk from individual cows may contain the A2 form of the beta-casein protein only, or a slightly different form of beta-casein known as A1 milk protein only, or a combination of the two. 

• This means that standard cow’s milk in the UK, US and most other developed countries provides a mixture of both A1 and A2 milk protein.^5–8

Proteins are made of long chains of different amino acids linked together, which can fold and twist into complex 3-dimensional shapes, allowing them to carry out their many different roles in the body and brain.

When consumed in food and digested, proteins are broken down into shorter chains (called peptides) or to individual amino acids, which can then be used up or re-assembled into new proteins as needed.

The beta-casein protein found in cows’ milk contains 209 amino acids, and very slight differences in these are found in milk from different cows.  

• Just one different amino acid (at position 67) is used to distinguish A2 from A1-type milk proteins.^5–9

A2 protein is the form of beta-casein found in human breastmilk,^8,10 and also in some – but not all – cow’s milk.^5–9

3)    Where does A2 protein milk come from?

Human breastmilk contains an A2-type form of beta-casein.^8,10,11  Similarly, A2 is also the main form of the beta-casein protein in all other animal milks except for standard cows’ milk - including goat’s and sheep’s milk (as well as milk from donkeys, camels, native buffalo etc).^8,12,13

A2 protein milk can also be obtained from cows with a particular genetic ancestry – because this is what determines whether their milk contains A2 protein, A1 protein, or a combination of the two.^5–9

Native cattle in many parts of Asia and Africa produce milk that contains only A2 protein. Some other breeds, such as Guernsey cows, produce mainly A2 protein milk.  But most breeds have more varied ancestry, so the proportions of A1 and A2 protein in their milk will differ between cows.^5–9  

• This means that cow’s milk from mainstream dairy herds in the UK and Europe, the USA, Australia and New Zealand contains a mixture of both the A1 and A2 protein forms.

However, simple genetic testing can identify those cows whose milk contains only the A2 form of beta-casein – so in some countries, ‘A2 cows’ milk’ is available, derived from dairy herds made up exclusively of cows selected for producing only A2 beta-casein in their milk (by simple non-invasive genetic testing).

4) What makes A2 protein milk different?

The differences between A2 protein milk and ordinary cows’ milk (which also contains A1 protein) follow from what happens during their digestion.¹⁴ 

The tiny structural difference in the A2 protein means that during digestion, this form of beta-casein breaks down differently from the A1 form. 

This leads to formation of a different balance of protein fragments called peptides: short chains of amino acids with biological effects.^14–17

Many of the benefits associated with consuming milk proteins - for heart health, energy metabolism, immune regulation and cancer prevention among others – come from the actions of different peptides that are released when milk proteins are broken down.^1,2,18,19

Some evidence indicates that consuming milk containing A2 protein only may reduce the digestive discomfort that some people experience after consuming standard cow’s milk.^20–22

This is thought to be because some of the peptides created by the digestion of A2 beta-casein are less likely to trigger ‘intolerance’ reactions in vulnerable individuals than those released when A1 beta-casein is digested.

Very importantly, intolerance reactions to milk are not the same as milk allergy (which can be identified via medical tests).

Individuals with a classic cow’s milk allergy need to avoid all dairy products -including A2 versions - and follow professional advice to ensure their diet provides all the nutrients and energy they need.

6) Are there any benefits of drinking A2 protein milk?

There are good scientific reasons why drinking A2 protein milk may have benefits for some people,^7,23–25 but most evidence for this comes from experimental or animal studies,^{26,27,36–38,28–35} or from general population studies that are purely observational,^39,40 and so can’t establish cause-and effect.⁸ 

For clear evidence of causal effects, human clinical trials (involving random allocation, placebo-control, and double-blinding) are needed.  

There are a few such trials of A2 protein milk – but only in adults, and mainly for digestive symptoms indicating milk intolerance.²⁵

In two clinical trials, Chinese adults with intolerance to lactose (the sugar in milk) showed significantly fewer digestive symptoms when drinking A2 protein milk versus standard cow’s milk.^21,22  Their attention and memory performance (as measured via computerised tests) was also better when consuming A2 protein milk compared with standard cows’ milk.²¹

Another randomised controlled trial found that in US adults, drinking A2 protein milk led to higher blood levels of a key antioxidant enzyme (glutathione), but other measures of health or wellbeing weren’t included.⁴¹

• More research is still needed to confirm other possible benefits of A2 protein for health and wellbeing – and any such benefits may only apply for particular individuals or subgroups who have higher-than-average risks for digestive, immune or other health issues.

Meanwhile, one important potential benefit of A2 protein milk can be in allowing individuals who would otherwise avoid milk to include this highly nutritious food in their diets.⁴

Anecdotal reports suggest possible benefits for some children and adults from consuming A2 protein milk rather than standard cows’ milk – typically for digestive symptoms (particularly constipation) - but also ‘chronic stuffy nose’, wheeze or bronchitis, eczema; and difficulties with memory, attention and concentration (often called ‘brain fog’).

There is a plausible scientific rationale (involving complex links between the gut, brain and immune system) for why A2 protein milk could make such positive differences for some people.^{7,26,35–38,27–34}

However, more research is still needed to find out exactly which individuals or subgroups of the population may derive any health benefits from consuming milk that contains the A2 form of the beta-casein protein only, compared with standard cows’ milk (containing both A1 and A2 beta-casein).

References

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