In the first human trial, subjects on a diet of A2 milk reported less abdominal pain, compared to a diet of regular A1 milk.

The Curtin University study, funded by the A2 Milk Company, has been published today in the European Journal of Clinical Nutrition, by the Nature Publishing Group.

Less than 5 per cent of the population are medically diagnosed with an allergy to milk, lactose, but there are an unknown number of people self-diagnosing intolerance.

For nearly 20 years, there have been claims that the A2 beta-casein protein is easier to digest than A1, but it's been dismissed as unscientific.

This pilot study at Curtin University, by Associate Professor Sebely Pal of the School of Public Health, found subjects on an A2 milk diet reported less bloating abdominal pain, and firmer stools, by staying off A1 beta-casein.

"The surprising finding in this study is that ordinary milk drinkers, who did not consider themselves to be milk-intolerant, found they had slightly softer stools when they consumed A1 as opposed to A2 milk.

"These softer stools can be associated with increased abdominal pain and this was highly significant."

Curtin University recruited 41 people, for a double-blind randomised trial over eight weeks.

They were asked to consume no dairy for two weeks, followed by two weeks of either A1 or A2 beta-casein milk. This was repeated and reversed after two weeks.

The subjects were asked to record their responses.

"The results show there is a difference in gastrointestinal responses in some adults consuming the A1 versus A2 beta-casein type," Professor Pal said.

"The logical next step is to source further funding for more scaled human studies to further understand the digestion differences."

One European scientist reviewing the research for the Journal wrote:

"The study is performed on 41 volunteers; that is sufficient to obtain statistically significant pilot data.

"These are very important for medical science and require confirmation in a larger study of participants with perceived intolerance to ordinary A1 beta-casein containing milk."

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Listen Duration: 4 minutes 52 seconds 4 m 52 s Associate Professor Sebely Pal of Curtin University says her pilot study into A2 milk made significant findings that need longer and larger verification. ( Sarina Locke ) Download 2.2 MB

Beta-Casein

Cows milk contains either A1 or A2 beta-casein protein.

A mutation occurred nearly 10,000 years ago in dairy cows in Europe which produced A1 as the dominant breed. Africa and India, by contrast, have A2 cows.

Animal studies of the beta-casein has shown 'digestion of A1 but not A2 beta-casein affects gastrointestinal motility and inflammation through the release of beta-casomorphin-7'.

Never before has the digestion been studied in people.

DNA selected A2 Cows

Selecting his herd for A2 beta-casein protein, Michael Perrich at Leppington Pastoral DNA tested a hair from the tail of each cow.

At Leppington, 1,500 cows have been selected with the A2 gene and are milked separately to the remaining A1 cows. The milk is kept separate, with the A2 milk going to the nearby A2 processing and bottling plant in outer south-west Sydney.

Leppington is owned by the Perrich family supplied the A2 milk for the trial in Perth.

The Perrich family have a stake in Freedom Foods, which is the largest shareholder of A2.

For Michael Perrich, the A2 milk story is about bringing people back to dairy.

"A lot of people have moved away from dairy due to digestion issues or just intolerances they've felt when they drink milk, and they've moved to non-dairy, and so they've come back because they can digest the (A2) milk better."

He hopes this is not the end of the research.

"With any trial it would be good to see something like that replicated."

Dairy Australia, the research and development corporation, has made no comment on the Curtin University research.

But dairy analysts say they won't be satisfied with anything less than a long-term and large health study.

The A2 Milk business

The results represent a significant boost to marketing of A2 milk by the A2 Milk company, the only one that produces milk free of A1.

Amid aggressive milk discounting by supermarkets, A2 has seen sales grow 12 fold in the last seven years.

In 2013, the A2 company recorded a $4 million profit, and its share of the fresh Australian milk market has grown from one per cent in 2008 to nine per cent in 2014.

The A2 Company, now owned largely by Australian interests is listed in New Zealand has had a 7 per cent drop in share price in the past 12 months.

Recently, copycat branding by Lion and Parmalat prompted consumer group Choice warn of spin, as is the milk is no different to before, and contains both proteins A1 and A2.