How did you start your day this morning? Did you have a bowl of your favourite cereal or weetbix with milk? Apparently, the average person consumes roughly 6,178 litres of milk in their lifetime, about half the volume of an Olympic size swimming pool!
Being a dairy addict (and a geek), every time I walk into the supermarket to get my milk, I get quite excited at the plethora of options on offer. The selection is truly diabolical, from the basic full cream, light and trim to ‘super’ variants of the latter, not to mention the organic range.
Recently, there has been a new addition to the dairy aisle of the supermarket, the ‘A2 milk’.
The companies that produce A2 milk claim that it is “milk as nature intended” and “milk that is better for you”.
Obviously my inner skeptic perked up! so I did a little digging and I must say, the issue is worth thinking about. Here’s what I found.
The protein perplexity : A bit of background
(Heads up! Science incoming)
Proteins are essentially the molecules that make up life; all tissues in the body are made up of these complex three-dimensional structural protein molecules. Proteins are in turn made up of strings of smaller molecules called amino acids, which each have unique chemical properties such as size, charge and chemical reactivity, which affect the way proteins interact in the body.
The amino acids are strung together like beads on a necklace to make proteins. The sequence of these amino acid ‘beads’, is determined by genes encoded in DNA. Genes are essentially codes made up of four chemical molecules called nucleotides which are arranged in different sequences to code for different information (like alphabets arranged differently to make different words).
You can think of genes as the ‘instructions’ to make proteins, if these instructions change, the protein’s amino acid sequence will (in most cases) change also. And this in turn, will affect the structure of the protein and hence it’s function.
There are various types of proteins. About 95% of cow’s milk is made up of two types of protein: caseins and whey proteins Beta-caseins are the second most-abundant protein in cows’ milk. Based on the sequence of amino acids in the protein, Beta-caseins found in cow’s milk can be further divided into 12 variants.
Two of these Beta-casein variants are especially relevant for our purposes: A1 and A2. A1 and A2 can be identified, because they both have a different specific amino acid located at position 67 in the peptide (protein) chain. Different cows naturally produce milk with variations in the amino acid at this position in the Beta-casein protein molecule. This occurs due to a naturally occurring variation in the genetic ‘instructions’. In A1 (normal milk-contains a mixture of A1 and A2) the amino acid Histidine at position 67 in the sequence, is substituted by another amino acid called Proline in A2 milk.
The point at issue: What does A2 milk offer?
Whether a particular cow produces A2 or A1 is significant because certain amino acids influence the breakdown of food. When A1 protein (normal milk) is broken down in the body, due to the presence of the Histidine amino acid, a protein fragment called ‘beta-casomorphin-7’ is created. Beta-casomorphin-7 (BCM7) is thought to lead to a number of human ailments (see below). It has, for example, been linked to Type 1 Diabetes, heart disease, Sudden Infant death Syndrome and Autism.
While the link between beta-casomorphin-7 and these diseases is still controversial, it has been suggested that people with a susceptibility to certain diseases should avoid milk that lacks the Histidine amino acid in casein (A1 or normal Milk).
In A2 milk the troublesome amino acid Histidine in the protein is replaced by a different amino acid called Proline, and is hence broken down by the body differently with no beta-casomorphin-7 being produced (negating related harmful effects).
Interestingly, human breast-milk and most other species have the A2 variant of Beta-casein!
A point of contention
Producers of A2 milk claim that this is “milk as nature intended”. This is not entirely accurate, since nature does not intend to do anything. Nature, works with spontaneous changes as raw material. This gives the impression that normal milk is somehow “un-natural”, which is unfair. Bovine milk originally only contained A2 beta casein. The mutation seems to have occurred spontaneously (this happens, more often than you think… such is nature) in European cow breeds (which could explain the increased prevalence of health ailments linked to dairy in Europe compared to Asia). Cows in other parts of the world such as Asia still produce the A2 version of Beta-casein in their milk. The point is both types of milk are found in nature, we are not paying homage to ‘nature’ by consuming A2 milk.
A poisoned chalice? Health Issues with milk (A1)
- Epidemiological evidence shows increased rates of Type-1 diabetes and heart disease in countries where A1 milk is consumed in large quantities. Animal studies have been able to show a “cause and effect relationship” with A1 Beta-casein consumption and oxidized LDL cholesterol and a consequent increase in arterial plaques (think heart attacks).
- In babies, BCM7 has been prime suspect for Sudden Infant Death Syndrome (SIDS). The tight junctions between cells in the intestine are not completely formed until after 12 months of age. Casomorphins (products of casein metabolism) have been found in the brainstems of children who died of SIDS. It may be that some children have genetically determined lower levels of the enzymes that breakdown BCM7 and are more at risk. Children who suffer from apnoea a condition where breathing is arrested for short periods of time) show higher blood levels of BCM7. Interestingly, bovine BCM7 is also found in the blood of infants only on breast-milk, suggesting that BCM7 from mum’s diet may be passed on through breast-milk.
- Autism is a much contested health issue lately. Studies show that BCM7 can cross the blood brain barrier and may aggravate autistic behaviour (increase symptoms in autistic children, NOT cause Autism). Autistic children often suffer from digestive complaints, and it may be that a ‘leaky gut’ leads to increased absorption of BCM7.
- Another major issue with dairy is milk intolerance (not to be confused with an allergy, which is an immune response). Milk intolerance is caused by the inability to digest lactose, which is still found in A2 milk. Nonetheless, consumers have reported an increased ability tolerate A2 milk. This could be because of the absence of BCM7 which specifically causes intolerance in some people. BCM7 also functions to slow down the passage of food in the gut, allowing more time for lactose fermentation, which leads to the production of gas. In A2 milk, the absence of BCM7 leads to decreased lactose fermentation and due to quicker passage in the gut.
- Milk allergies are caused by the body mounting an immune response specific milk proteins. Allergies associated with BCM7 can cause eczema and asthma. BCM7 also stimulates the production of proteins that make mucus (think snot or chesty cough) sticky. So A2 milk consumption may relieve these symptoms.The composition of normal milk and A2 milk is similar except for the beta-casein molecule, so A2 milk may still not be suitable for those who are allergic to other milk proteins, so it is best to seek medical advice in situations where allergy is an issue.
Who is at risk?
If you love dairy, there’s no need to panic. This could actually be a good thing. Here’s why…
The health concerns of A1 milk are thought to stem from the intestinal absorption of BCM7. A2 milk may be a better alternative for those more likely to absorb excess BCM7 due to a damaged gut. People who suffer from stomach ulcers, Crohn’s Disease, Coeliacs’s Disease may do well to stick to A2 milk. Additionally, people at risk of diabetes and cardiovascular disorders may also benefit from switching to A2 milk.
Milk mechanics: How is A2 Milk made?
A2 milk is produced from cows that naturally produce milk with the A2 version of beta-casein. These cows naturally have genetic instructions that code for milk casein proteins with a different amino acid at the specified position. According to A2 Corporation (a major A2 milk supplier), sires carrying the desired genetic variation can be identified through a simple DNA test performed on cow tail hairs (no invasive testing). Cows carrying the gene are then bred to create offspring that produce milk with the desired qualities, owing to the right composition of…
Importantly, there is no genetic engineering involved in the production of A2 milk! (How about that, hippies ;)?). There is no introduction of foreign genes from other species and no tampering with the natural genetic code of the cows. In fact, this method of breeding animals with desired properties has been performed by humans since Neolithic times…only we called it “farming”or “husbandry”.
There has been some contention about the validity of suggested health benefits pertaining to A2 milk (see references). Although more studies are required to establish a direct cause and effect relationship, current evidence shows that A2 milk does not pose any risk to human health not already associated with A1 milk and may in fact offer many benefits.
There is a general misconception that advances in genetics cannot be applied to food production without interfering with nature or creating a ‘Franken-food’. Selection for naturally occurring genetic variation is an ancient concept. Only now, we have advanced technologies to enhance the efficiency of this process, especially with a view to upgrading the nutritional value of consumed foods.
Regardless of the controversy surrounding the benefits of A2 milk consumption, this is a classic example of implementing genomic technologies to improve animal breeding refining food production and benefitting human health.
That’s it for today folks! Thanks for reading!
Woodford, K. (2009). Devil in the Milk: Illness, Health and the Politics of A1 and A2 Milk. Chelsea Green Publishing.
Ho, S., Woodford, K., Kukuljan, S., & Pal, S. (2014). Comparative effects of A1 versus A2 beta-casein on gastrointestinal measures: a blinded randomised cross-over pilot study. European journal of clinical nutrition, 68(9), 994-1000.
Truswell, A. S. (2005). The A2 milk case: a critical review. European journal of clinical nutrition, 59(5), 623-631.
Woodford, K. B. (2006). A critique of Truswell’s A2 milk review. European journal of clinical nutrition, 60(3), 437-439.
Bell, S. J., Grochoski, G. T., & Clarke, A. J. (2006). Health implications of milk containing β-casein with the A2 genetic variant. Critical reviews in food science and nutrition, 46(1), 93-100.
Allison, A. J., & Clarke, A. J. (2006). Further research for consideration in/the A2 milk case/\’. European journal of clinical nutrition, 60(7), 921-924.
Sodhi, M., Mukesh, M., Kataria, R. S., Mishra, B. P., & Joshii, B. K. (2012). Milk proteins and human health: A1/A2 milk hypothesis. Indian J Endocrinol Metab, 16(5), 856.