According to new research, lactose intolerance may be a myth for many, with resulting symptoms from drinking milk most likely an inflammatory response to the A1 protein found in conventional cow's milk.
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Published in the U.K.-based Nutrition Journal, the study led by Professor Sun Jianqin from Huadong Hospital, an affiliate of the Fudan University in Shanghai, China compared the impact of humans drinking conventional cow's milk – milk with the A1-protein – to that of milk that is A1-protein free.
China has been chosen for clinical research due to the high prevalence of lactose intolerance in the country (nearly 90% of population reports lactose intolerance).
First human study-based research testing the effects of the A1 versus A2 protein types on participants with clinically diagnosed lactase deficiency/lactose intolerance.
Conventional cow's milk (containing A1 protein type) caused significantly higher gastrointestinal inflammation, stool transit delays, and elevated blood markers for inflammation and immune response compared to milk containing only the A2 protein (free-from the A1 protein type).
The study was supported by The a2 Milk Company, an Australian milk company specializing in milk from cows selected because they naturally produce only milk containing the A2 protein type.
After overwhelming success in Australia and more recently growing popularity in China, a2 Milk launched in the United States, with major plans for nationwide distribution.
The a2 Milk Company entered select U.S. markets, first in California, and is available in all major grocers, including Whole Foods, Sprouts and Fresh Market nationally.
"This research confirms the post-dairy digestive discomfort may not always be the result of lactose intolerance," said Jeff O'Neill, president, The a2 Milk Company, U.S.
"Lactose is what usually takes the blame for millions of people worldwide with digestive issues associated with ordinary cow's milk, leading many to give up milk altogether. The evidence is strong that an inflammatory response to the A1 protein may be the issue for a large proportion of people."
Originally, all cows only produced milk containing the A2 type of beta-casein protein. However, after domestication, another milk protein type – A1 protein type – appeared in European herds and spread along with human migration. A1 protein is contained in the vast majority of cow's milk consumed in the U.S. today.
A 2009 study published in Nutrition Today, found approximately 1-in-4 Americans (significantly higher proportions within Asian, African American and Hispanic populations) experience digestive issues when consuming conventional cow's milk, with the majority incorrectly associating these symptoms to lactose intolerance. The new China based research further supports these findings.
This Chinese research is the first human-based research testing the effects of the A1 versus A2 protein types on participants, half who were clinically confirmed as truly having issues with lactose digestion.
The trial found milk containing only the A2 protein type caused no gastrointestinal disturbance in any study participants, including those confirmed to have issues digesting lactose.
Study participants who drank conventional cow's milk (containing the A1 protein), experienced elevated gastro-intestinal inflammation, stool transit delays, and elevated markers for inflammation and immune response.
When participants drank milk containing only the A2 protein, it was significantly gentler on their digestive system, with less inflammation associated with bloating and abdominal pain.
According to contributing author, Associate Professor Xia, Gastroenterologist at the Shanghai Jiaotong University School of Medicine, and Adjunct Associate Professor at Johns Hopkins University School of Medicine, "These are significant findings for those who believe they suffer from lactose intolerance.
"The research suggests milk that only contains the A2 type protein (A2 beta-casein) has a natural affinity with the human body and digestion. Gut inflammation caused by the A1 type protein can be avoided by consuming milk products with only the A2 type protein.
"With so many people believing they are lactose intolerant, both in China and around the world, the findings are truly noteworthy." ■