COULD the type of milk you are drinking be leading to digestive discomfort?
It’s a question Curtin University researchers are hoping to answer by comparing A1 and A2 milk, where there is a very small difference in the structure of the beta-casein protein.
School of Public Health research assistant Dr Suleen Ho said the A1 variant arose from a Proline67 to Histidine67 point mutation of the progenitor in European herds 5000 to 10,000 years ago.
“Because of this difference, A1 beta-casein leads to the release of the betacasomorphin-7 (BCM-7) peptide, which may be impacting on a variety of tissues and organs,” she says.
“The regular milk available in supermarkets has not been tested to determine the amount of A1 and A2 beta-casein protein but, based on the breed of cows used, it would be mostly A1.
“The difference in cost for A2 milk is due to the DNA testing of the cows to determine if they are A2 producers.
“Other than this upfront cost, production would be about the same – although the milk currently needs to be processed separately from non-A2 producers.”
While many attribute digestive discomfort to lactose intolerance, it only affects about 32 per cent of people who receive this discomfort from milk consumption.
However, the remainder could be put down to a non-allergic reaction against cow's milk protein.
“People have a variety of problems with A1 milk, such as gastrointestinal issues and chronic diarrhoea or constipation,” Dr Ho says.
“They have also reported sinus problems with stuffy and runny noses and rashes, which clear up after switching to A2 milk.
“Not a lot of research has been done in this area yet and improvements are from anecdotal evidence.
“Animal studies do implicate BCM-7 in digestive problems but specific mechanisms are still unclear.”
As part of the Curtin study, headed by Associate Professor Sebely Pal, the research team will be using gastrointestinal symptom diaries to compare digestive discomfort between A1 and A2 milk, also taking blood samples to test levels of BCM-7.
They will also measure gut permeability with a five-hour urine collection and gut inflammation by analysing levels of calprotectin in faecal samples.
The study will test people between 18 and 65 with no milk allergies, no diagnosed lactose intolerance, are not pregnant or lactating, no cardiovascular events in the past six months, do not take opioids, have not received antibiotic treatment in the past two months and have not taken immunosuppressive medications or anti-inflammatory drugs in the past four weeks.
A2 Dairy Australia is providing the funding and milk for the research.