New research reaffirms role of A2 protein in lactose intolerance

A new clinical trial has reaffirmed the idea that the A1 beta-casein protein in cow’s milk is the root cause of lactose intolerance, and not the lactose itself, highlighting the value of brands such as a2 Milk.

The trial, conducted in China and published in Nutrition Journal, involved 600 adults who said they were lactose-intolerant.

The Chinese researchers investigated the ‘acute’ impacts of drinking 300ml of milk on symptoms often associated with milk intolerance, with the effects being measured after one, three and 12 hours.

Those symptoms included flatulence, bloating, abdominal pain, and both the frequency and consistency of stool.

The study concluded that “milk containing A2 beta-casein attenuated acute gastrointestinal symptoms of milk intolerance, while conventional milk containing A1 beta-casein reduced lactase activity and increased gastrointestinal symptoms”.

The results are good news for a2 Milk, the Australian dairy company which separates the two proteins found in natural cows’ milk in order to offer products that are easier to digest for consumers who would otherwise be lactose-intolerant.

Depending on a cow’s genetic make-up, milk traditionally contains either A1 or A2 proteins, or a mix of both – but simple genetic tests can determine whether individual members of the herd produce milk that is A1/A1, A1/A2, or A2/A2.

Conventional dairies pool their milk during processing, but a2 Milk has built its brand on using cattle that fall exclusively into the latter group.

The brand has already received a vote of confidence in the form of a study, published in December, which suggested that A2 protein doubles the concentration of the essential antioxidant glutathione – a critical part of the body’s defence system.

The latest research adds weight to similar but smaller clinical trials that also found a link between the two beta-casein proteins in cow’s milk and lactose intolerance. The first – conducted at Curtin University in Australia – showed that milk with only the A2 protein is easier on the digestive system. 

Last year, another small-scale study in China showed that those with lactose intolerance can drink A2 milk with no digestive discomfort.

Dr Anton Emmanuel, a consultant gastroenterologist at University College Hospital in London, said: “This is the largest human trial to date examining the differences between the impact of the A1 and A2 protein. It suggests that proteins found in dairy can have a significant impact on digestion, and that lactose may not be the only cause of gastrointestinal issues in those with an intolerance – around 60% of the world’s population.

“Given that the underlying biochemistry and symptoms of lactose intolerance are identical in Asian and Caucasian/British populations, these results are highly significant to both regions.”

Analysis: How many people are lactose-intolerant?

Studies have shown that around 60% of people on a global basis suffer from lactose intolerance – that’s over 4.5 billion people – but that figure is heavily dependent on race. Northern European consumers are more easily able to produce the enzyme lactase into adulthood, which then helps them digest milk, compared with people of Asian or African descent. This is why the A2 Milk Company, which isolates the A2 beta-casein protein in its milk, says that as many as 90% of Chinese consumers are lactose intolerant. But with an increasing number of people avoiding dairy for health and lifestyle reasons and with the availability of products like a2 Milk, which allow anybody to consume cow’s milk that is easy to digest, it’s difficult to discern how much of the world is truly incapable of drinking milk.