Emulsifiers, a common food additive, can alter the gut microbiota composition and localization to induce intestinal inflammation that promotes the development of inflammatory bowel disease (IBD) and metabolic syndrome. Emulsifiers are added to most processed foods to aid texture and extend their shelf life. The research team suggests that the current means of testing and approving food additives may not be adequate to prevent use of chemicals that promote diseases driven by low-grade inflammation and/or which will cause disease primarily in susceptible hosts.
The research team fed mice two very commonly used emulsifiers, polysorbate 80 and carboxymethylcellulsose, at doses seeking to model the broad consumption of the numerous emulsifiers that are incorporated into almost all processed foods. They observed that emulsifier consumption changed the species composition of the gut microbiota and did so in a manner that made it more prone to inflammation. The altered microbiota had enhanced capacity to digest and infiltrate the dense mucus layer that lines the intestine, which is normally, largely devoid of bacteria; and alterations in bacterial species resulted in bacteria expressing more flagellin and lipopolysaccharide, which can activate pro-inflammatory gene expression by the immune system.
Changes in the bacterial population triggered chronic colitis in mice genetically prone to this disorder, due to abnormal immune systems. On the other hand, in mice with normal immune systems, emulsifiers induced low-grade or mild intestinal inflammation and metabolic syndrome, characterized by increased levels of food consumption, obesity, hyperglycemia and insulin resistance. These side effects of emulsifier consumption were eliminated in germ-free mice, which lack a microbiota. Transplant of microbiota from emulsifiers-treated mice to germ-free mice was enough to transfer some parameters of low-grade inflammation and metabolic syndrome, indicating a central role for the microbiota in mediating the adverse effect of emulsifiers.
Researcher Andrew T. Gewirtz said, "We do not disagree with the commonly held assumption that over-eating is a central cause of obesity and metabolic syndrome. Rather, our findings reinforce the concept suggested by earlier work that low-grade inflammation resulting from an altered microbiota can be an underlying cause of excess eating." Researchers are now testing additional emulsifiers and designing experiments to investigate how emulsifiers affect humans.
The research is published in 'Nature'.