Photo: Sharyn B (flickr)
Researchers say new evidence bolsters a theory that milk from the majority of cows in the U.S. contains a possible intestinal irritant. Most of the milk cows in the U.S. and Europe produce milk with a mutated protein known as A1 beta-casein. Milk from Asian and African bovine breeds only contains an older form of the protein, A2 beta-casein.
The new study, published in the International Journal of Food Sciences and Nutrition, found that rats that drank A1 milk digested their food more slowly than rats that drank the A2 milk, and suffered from some bowel inflammation. The study follows reports earlier this year that a New Zealand company plans to market A2 milk in North America.
The new research lines up with anecdotes from African and Asian immigrants who claim they can drink milk at home, but U.S. milk makes them sick.
When digested, A1 beta-casein breaks down into a bunch of protein fragments, including one known as BCM-7. That peptide has opium-like characteristics that could be absorbed through a person’s intestinal wall, slowing peristalsis to an uncomfortable crawl.
Keith Woodford, professor of farm management and agribusiness at Lincoln University in New Zealand and co-author of the study, has been a steadfast champion of A2 research. He said a growing body of evidence is showing that a significant number of people who complain about gas after consuming dairy might not actually be lactose intolerant.
“If food is delayed going through the system, even a small amount like 10-20 percent, that would allow 2-3 times the fermentation,” he said.
Woodford said trying goat’s milk is an easy and safe way to test whether A1 milk might be a bigger culprit than lactose, because goat milk contains lactose but not BCM-7.
“As a front-line strategy, it has been incredibly successful in dealing with digestive issues,” he said.
There’s been a lot of debate about the benefits of A2 milk over the years, and plenty of critics remain unconvinced. Naysayers include New Zealand’s department of food standards, which took Woodford to task for suggesting that A1 milk could pose health risks for some consumers. At issue is whether significant amounts of that BCM-7 culprit is able to enter the bloodstream. A release blasting Woodford’s claims cited an earlier study that concluded “insufficient overall evidence that either milk has benefits over the other.”
The European Food Safety Authority published a report in 2009 declaring that “a cause and effect relationship is not established between the dietary intake of BCM7, related peptides or their possible protein precursors and non-communicable diseases.”
Woodford says persistent critics have dismissed evidence because “there’s a lot of strong forces out there that wish this would just go away.”
“Everything that’s written (about A2 milk) will get attacked because there are elements of the mainstream industry that are very scared of this,” he added.
About 25 percent of Americans and 75 percent of the world population suffer from lactose intolerance. Most mammals stop producing the lactose-breaking enzyme after weaning, but research has shown that a human mutation some thousands of years ago allowed some early Europeans to be lifelong milk drinkers.