a2 Milk™ digested differently to conventional milk

“We found a strikingly different pattern of digestive symptoms in people we identified as lactose intolerant after drinking a2 Milk™ compared to conventional milk,” says study lead Dr Amber Milan, a Research Fellow at the University of Auckland-based Liggins Institute, which is conducting the research jointly with AgResearch, a nationally owned research institute supporting New Zealand’s agriculture.

“a2 Milk™ was at least as effective as lactose-free milk at preventing or easing some of the symptoms of lactose intolerance, including nausea, stomach pain and bloating, but didn’t reduce levels of flatulence and gastric reflux,” says Dr Milan.

The women’s self-ratings of ‘overall digestive comfort’ were the same after a2 Milk™ as after regular milk, suggesting over the course of 12 hours, the other symptoms were unpleasant enough to not shift overall digestive comfort.”

Conventional milk contains both the A1 and A2 types of beta-casein, a protein comprising 25-30 percent of total milk protein. It’s thought that originally all cows produced only the A2 protein type, and the A1 mutation appeared 5000-10,000 years ago. a2 Milk ™ comes from cows that naturally produce only the A2 type.

“There is some evidence that the symptoms of lactose intolerance may be influenced by the proteins in milk,” says AgResearch senior research scientist Matthew Barnett. “We wanted to investigate this more closely.”

Globally, about 70 percent of adults consider themselves lactose intolerant, and experience bloating, nausea or other unpleasant symptoms after consuming it.

The study was the first to compare the digestive response to conventional milk, a2 Milk™ and lactose-free conventional milk between people who are able to digest lactose, people with lactose intolerance and people with dairy intolerance. It was funded through the New Zealand Government High-Value Nutrition National Science Challenge, with co-funding from The a2 Milk Company Limited.

Participants were 30 healthy young women (aged 20-30, BMI in the normal range) who said they had trouble digesting milk, and a control group of 10 dairy-consuming women. First they drank 50g of lactose – equivalent to about a litre of milk – to determine if they had lactose intolerance or not. Then, on three separate visits, the same women drank 750ml of the three types of milk.

Immediately after the women consumed the milk, and at 30 minute intervals for three hours, the researchers took blood, urine and breath samples, measured their waist, and performed MRI scans. The women also recorded how they felt for the 12 hours following consumption.

Analysis revealed that the lactose intolerant women:

• did not feel nauseous or have an urgent need to go to the toilet after drinking a2 Milk™ and lactose-free milk, but did after drinking conventional milk

• had fewer bowel movements over the three hours both after a2 Milk™ and lactose-free milk compared to conventional milk

• were half as likely to report abdominal pain, fullness and bloating over the course of 12 hours both after a2 Milk™ and lactose-free milk relative to conventional milk

• experienced a smaller and later rise in breath hydrogen after a2 Milk™ versus conventional (breath hydrogen is a by-product of gut bacteria digesting any lactose that isn’t absorbed by the body, and is partly responsible for symptoms like bloating and flatulence)

• experienced the same levels of flatulence and gastric reflux after drinking a2 Milk™ and conventional milk, self-reported similar levels of “overall digestive discomfort” both after a2 Milk™ and conventional milk (lactose-free milk was rated most comfortable on this measure)

• experienced a higher spike in insulin levels immediately after drinking lactose-free milk, but not after a2 Milk™ and conventional milk (to be expected because lactose-free milk is created by breaking down lactose into two simple sugars). Spikes in insulin can affect metabolism in many ways, for example lowering blood sugar and making you feel hungrier sooner

Dr Milan says animal studies show a breakdown product of the A1 protein causes inflammation in the small intestine, which seems to somehow exacerbate lactose intolerance.

“What our findings suggest is while we can’t fix the inability to digest lactose, we might be able to minimise the exacerbating action of the A1 protein.”

The researchers also showed that dairy intolerance is distinct from lactose intolerance. Dairy intolerant women reported all three milk types as equal in terms of digestive discomfort over the first three hours.
A planned second study by the same team will track the effects of a2 Milk™ on gut comfort over two weeks, focusing on small intestinal inflammation.

Dr Milan will present the current findings at the Food and Nutrition Conference and Expo hosted by the American Academy of Nutrition and Dietetics on October 22.

[This press release was originally issued by Liggins Institute(external link)]