Diets high in saturated milk fats, found in processed foods and sweets, may increase the risk of developing immune disorders like inflammatory bowel disease in those who are genetically predisposed, a study of mice found.
About 60 percent of mice fed a diet high in saturated milk fats developed ulcerative colitis, an autoimmune inflammatory bowel disease, within six months, compared with about 25 to 30 percent of the animals who ate a low-fat diet or one high in polyunsaturated fats such as safflower oil, according to research online today in the journal Nature. The severity and extent of the colitis was much greater in the mice fed milk fats than those fed low-fat diets, the study found.
Autoimmune disorders such as inflammatory bowel disease, which include colitis and Crohn’s disease, are more common now than 50 to 100 years ago, Eugene Chang, a senior study author, said. Today’s findings show that environmental factors including food may be contributing to the rise in these and other immune disorders like asthma, he said.
“These immune disorders are all linked together. As we’re beginning to understand the basis of these diseases they have very common mechanism of actions that seem to cause them,” said Chang, a professor of medicine at the University of Chicago, in a June 11 telephone interview.
“They’re a combination of genetic susceptibility and changes in environment,” he said. “In most cases the environment alters the microbes that we live with and that alters our relationship with our microbes. In most people, that relationship we can compensate for but certain individuals have a mutation or genetic factor that might cause them to react in an abnormal way.”
Saturated fats are those that are solid and are found, for example, in high-fat cuts of meat and cheeses and whole milk. Milk fat is a type of saturated fat that’s left over when the fat has been separated from butter and dehydrated into a powdered substance. Milk fats are found in ice cream and chocolate products such as chips and candy.
The researchers found that mice fed a diet high in milk fat had more of a bacterium called Bilophila wadsworthia in their gut than those fed other diets.
Milk fats are hard to digest, requiring the liver to secrete a form of bile high in sulfur to help break them down in the intestines, the researchers said. Bilophila wadsworthia thrives on sulfur so when the fats reach the colon the bacteria numbers increase. The bacteria can then activate the immune system in those genetically prone to bowel diseases causing colitis, they said.
“Environment plays such a huge role in human disease,” Chang said. “In our study we are what we eat. If you had a genetic abnormality and you grew up in parts of Africa or rural areas of Asia you may not get any of these disorders but if you come to a culture where the environmental signals and stimuli are completely different and very artificial that may set off a whole new relationship between you and the environment and increase your risk for these disorders.”
Chang and Suzanne Devkota, a lead study author and post-doctorate student at Harvard Medical School in Boston, said more studies are needed to show whether a diet rich in milk fats causes autoimmune diseases in humans and if changing the foods people eat can reverse the diseases or prevent them from occurring in those genetically predisposed.
The findings also don’t account for potential environmental triggers for autoimmune diseases such as different dietary components including the amount of lard or processed sugars eaten which have been tied to the illnesses, Chang said.
Today’s study was funded in part by the U.S. National Institutes of Health, the Gastrointestinal Research Foundation and the Crohn’s and Colitis Foundation of America.