Common additives in ice cream, margarine, packaged bread and many processed foods may promote the inflammatory bowel diseases ulcerative colitis and Crohn's disease as well as a group of obesity-related conditions, scientists said on Wednesday.
The researchers focused on emulsifiers, chemicals added to many food products to improve texture and extend shelf life. In mouse experiments, they found emulsifiers can change the species composition of gut bacteria and induce intestinal inflammation.
Such inflammation is associated with the frequently debilitating Crohn's disease and ulcerative colitis as well as metabolic syndrome, a group of conditions that increase risk for type-2 diabetes, heart disease and stroke.
Mice were fed emulsifiers diluted in drinking water or added into food, which were found to trigger low-grade intestinal inflammation and features of metabolic syndrome such as blood glucose level abnormalities, increased body weight and abdominal fat weight.
Consuming emulsifiers increased the risk of colitis, mimicking human inflammatory bowel disease, in mice genetically susceptible to the condition, the study found.
Georgia State University microbiologist Benoit Chassaing, whose study appears in the journal Nature, said the effects seen in mice "may be observed in humans as well."
The study involved two widely used emulsifiers, polysorbate 80 and carboxymethylcellulose. The researchers are planning human studies and are already studying other emulsifiers.
Emulsifiers are used in margarine, mayonnaise, creamy sauces, candy, ice cream, packaged processed foods and baked goods. They can make products like mayonnaise smooth and creamy instead of an unappetizing amalgam of water and oily globules.
A key feature of inflammatory bowel diseases and metabolic syndrome is a change in the gut microbiota - the roughly 100 trillion bacteria that inhabit the intestinal tract - in ways that promote inflammation. In mice given emulsifiers, the bacteria were more apt to digest and infiltrate the dense mucus layer that lines and protects the intestines.
Incidence of inflammatory bowel disease and metabolic syndrome started rising in the mid-20th century at roughly the same time that food manufacturers began widespread emulsifier use, the researchers said.
"We were thinking there was some non-genetic factor out there, some environmental factor, that would be explaining the increase in these chronic inflammatory diseases," Georgia State immunologist Andrew Gewirtz said.
"And we thought that emulsifiers were a good candidate because they are so ubiquitous and their use has roughly paralleled the increase in these diseases. But I guess we were surprised at how strong the effects were."