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A1 or A2?

Cows' milk contains a protein called beta casein, which comes in several forms depending on the genetic makeup of the cow - but what is the difference, and why does it matter?

Molecules in milk

Milk is a mixture of water, fats, proteins, sugars, and minerals. Cows’ milk contains six main proteins, one of which is called beta-casein (β-casein). β-casein makes up around 30% of the protein in cows’ milk and comes in different varieties, including A1 β-casein and A2 β-casein. A cow can produce one or more forms of β-casein, depending on her genetic make up.

A1/A2 beta casein and human health

The form of β-casein present in in milk may have implications for human health. It has been suggested that the A1 β-casein might lead to or aggravate Type I diabetes, heart disease, schizophrenia and autism. Whereas, A2 β-casein is not associated with these diseases and might consequently be better for you. Because of these findings a2 Milk™, which has naturally maximised levels of A2 β-casein, is now being produced and marketed in New Zealand and overseas.

Truth or rumour?

In 2004, the New Zealand Food Safety Authority (NZFSA) employed an expert, Professor Boyd Swinburn, to examine the current research on A1 and A2 β-caseins and human health. He reported that:

  • Countries with high consumption of A1 β-casein had high rates of Type I diabetes and heart disease; and
  • Some individuals with schizophrenia or autism show improvement when put on a casein- and gluten-free diet.

He concluded that there was no direct evidence to support claims that A1 β-casein played a role in disease, but that it was worth further investigation.

Breeding cows for β-casein

Some farmers are using selective breeding methods to create herds of cows that only produce milk containing A2 β-casein. In other words, only calves produced by bulls and cows that have the A2 β-casein gene will be kept on a farm. Using this method a farmer can increase the proportion of cows in their herd that produce the A2 β-casein protein in their milk over several generations.

Farmers can tell whether a cow will produce A1 or A2 β-casein using a DNA test developed in New Zealand by Livestock Improvement Corporation.

Get information sheet: Testing for the casein gene

Written by Sara Loughnane, NZ Science, Mathematics, and Technology Teacher Fellow, 2006.

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