Eating milk fats can cause colitis and other bowel diseases in some people, new research suggests.
University of Chicago researchers have found that milk fats alter the population of bacteria in the gut and can lead to inflammatory bowel diseases (IBD) in genetically susceptible people.
The experiments were conducted on mice that mimic human IBD. The mice were engineered so they couldn't produce interleukin 10, a molecule which acts as a brake on the immune response to gut bacteria, according to a press release from the university.
The researchers found that an uncommon microbe was found at much higher levels in mice fed diets containing concentrated milk fats.
Bilophila wadsworthia made up 6 per cent of the bacteria in the bowels of mice fed milk fats. In mice fed a low-fat or polyunsaturated fat diet, these bacteria were almost undetectable.
B. wadsworthia has previously been found at high levels in patients with IBD, appendicitis and other inflammatory disorders.
A diet rich in milk fats forces the liver to make a sulphur-rich form of bile to aid digestion.
Study author Eugene Chang said it was this bile which increased the levels of the harmful bacteria.
"Presented with a rich source of sulphur, they bloom, and when they do, they are capable of activating the immune system of genetically prone individuals."
Suzanne Devkota, a co-author of the study, explained that the bacteria interacted with the bile and actually amplified the immune response.
"By increasing the permeability of the bowel, they enhance immune-cell infiltration, and that can induce tissue damage."
Chang said changing diets were increasing the incidence of IBD.
"This is the first plausible mechanism showing step-by-step how Western-style diets contribute to the rapid and ongoing increase in the incidence of inflammatory bowel disease."
He said the results may provide an avenue for treatment of inflammatory disorders.
"Right now we can't do much about correcting genes that predispose individuals to increased risk for these diseases, and while we could encourage people to change their diets, this is seldom effective and always difficult.
"The balance between host and microbes can be altered back to a healthy state to prevent or treat these diseases. We are testing that right now."
The study was published in the journal Nature.
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