Processed foods are suspected of causing a variety of heath issues. Foods high in sugar and refined carbohydrates, for example, are known to cause high blood sugar and obesity. But recent research has uncovered an entirely new mechanism by which many metabolic disorders can be triggered. Certain additives that are commonly used in processed foods are being shown to impact health, at least in mice, by altering the body’s population of bacteria that live in the gut. Collectively referred to the microbiome, the importance of this bacterial community of millions is just beginning to be understood.

Research published last September demonstrated that artificial sweeteners can raise blood sugar levels in mice, stimulate their appetites, and possibly lead to obesity and diabetes. The artificial sweeteners appear to create these conditions by changing the micriobiome’s composition.  

Last month, a different set of research was published that also suggested a disease pathway mediated by microbiome disturbance. This time, commonly used food additives called emulsifiers are the culprits.

Emulsifiers help keep sauces smooth and ice cream creamy, they hold dressings together and prevent mayonnaise from separating into oil and water. The new research gives reason to suspect that emulsifiers could raise your blood sugar, make you fat and even make your butt hurt.

The study, published in Nature, looked at two common emulsifiers, Polysorbate 80 and carboxymethylcellulose (CMC), and found a range of metabolic problems that appeared in mice who were given water dosed with these chemicals in quantities proportional to what a human might consume. The mice who drank either emulsifier tended to eat more, gain weight and develop conditions like irritable bowel syndrome, colitis and metabolic syndrome, which is a range of pre-diabetic conditions.

The effects of these additives were dependent on the dosage; the more emulsifier the mice consumed, the worse off they were. A control group drank water laced with a common preservative, sodium sulfite, and did not show any negative effects on the gut.

The team found that the bacterial diversity of the mice microbiomes were altered. They also discovered the mucous membrane of the gut was thinner in mice who were fed emulsifiers. The thinner mucous membrane allowed the microbes closer to the gut wall than they would normally get, they wrote, which could cause the observed inflammation of the gut wall, and diseases like irritable bowel syndrome.

John Coupland, a professor of food science at Penn State University, thinks this research could be a game changer, providing it can be shown that these emulsifiers can do to humans what they do to mice. “[It] really challenges a lot of the way we think about assessing toxicology and nutritional value of foods,” he said in an email.

Coupland noted that Polysorbate 80 and CMC are very different molecules. While Polysorbate 80 is small, and doesn’t carry an electrical charge, CMC is large, and charged. These molecules are not only built differently, but they behave differently, he said, pointing out that CMC is technically not even an emulsifier, but a thickener that makes emulsions more stable. That they both cause similar microbial disruptions, mucous reductions and associated health problems is a striking discovery.  

In an email interview, the study’s co-author, Benoit Chassaing, acknowledged that CMC is more of a thickener than an emulsifier, but noted that it does have emulsification properties, due to its charge. He suspects the resulting emulsifying activity is to blame.