They found what’s making us fat and sick in processed foods

Sugar, salt, ingredients you need a college degree to pronounce let alone understand — there are a lot of reasons to eat less processed foods. But scientists just pinpointed a near universal ingredient that’s in processed foods and not others as a major culprit in metabolic syndrome and inflammatory bowel diseases like Crohn’s.

Emulsifiers, which are added for texture and to extend shelf life, are altering the microbiome in our gut, changing its composition and causing the migration of what are good bacteria in one area to where they’re causing problems like intestinal inflammation. Earlier studies have shown that even low-grade inflammation can cause overeating.

“The dramatic increase in these diseases has occurred despite consistent human genetics, suggesting a pivotal role for an environmental factor,” says co-author Dr. Benoit Chassaing of Georgia State University. “Food interacts intimately with the microbiota, so we considered what modern additions to the food supply might possibly make gut bacteria more pro-inflammatory.”

A healthy microbiome in the human gut contains about 100 trillion bacteria, which are rarely found in the intestines. But when those bacteria end up there, they cause inflammation that can lead to debilitating diseases like ulcerative colitis and metabolic syndrome, an umbrella term for obesity-related disorders that can lead to Type 2 diabetes and liver diseases.

The incidence of intestinal and metabolic diseases have shot up since the 1950s, when emulsifiers started becoming widely used in processed foods.

The researchers tested their theory by feeding mice two commonly used emulsifiers — polysorbate 80 and carboxymethylcellulsose — in doses that resembled a typical diet. The rodents’ microbiome tipped in favor of inflammation-causing bacteria, which moved into the intestines and ate away at the protective mucus that lines them.

This caused genetically predisposed mice to develop colitis, while mice with normal immune systems showed mild intestinal inflammation and symptoms of metabolic syndrome such as overeating, significant weight gain, high blood sugar and insulin resistance. These results were not seen in mice that had been bred to lack a microbiome.

The team is now testing a wider range of emulsifiers and designing human trials.They also warm that moderation with regard to any food remains key to better health.

“We do not disagree with the commonly held assumption that over-eating is a central cause of obesity and metabolic syndrome,” says co-author Dr. Andrew T. Gewirtz. “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.”