Additives that keep foods fresh may sour in the gut

Food additives may keep snacks fresh and tasty looking, but they can wreak havoc on the gut. These additives disrupt the intestine’s protection from bacteria and boost inflammation in mice, scientists report online February 25 in Nature.

The new research “underscores the fact that a lot of things we eat … may not be as safe as we think they are,” says Eugene Chang, a gastroenterologist at the University of Chicago.

Additives called emulsifiers help many foods, including ice cream, salad dressing, pasta sauce, bread and cookies, stay fresh on supermarket shelves. To see whether the additives play a role in inflammatory conditions, researchers fed emulsifiers to mice for 12 weeks.

The mice put on weight and made proteins that signal inflammation. More inflammation-causing microbes also showed up in the bacterial communities in the mice’s guts.

Mice engineered to lack gut bacteria experienced none of these effects after eating emulsifiers. But when the researchers transplanted bacteria from the first group of mice into the second group, the microbe-free mice developed the same symptoms.

Tests showed that bacteria had penetrated the layer of mucus that normally protects the cells lining the gut. This mucus layer also became thinner.

Emulsifiers may make the mucus layer more permeable, allowing certain bacteria to penetrate and cause inflammation, says study coauthor Andrew Gewirtz, an immunologist at Georgia State University in Atlanta. Bacteria are thought to infiltrate the mucus layer in inflammatory conditions such as Crohn’s disease and metabolic syndrome, a collection of symptoms that predispose people to problems such as diabetes and heart disease.

“Emulsifiers are a plausible candidate to have promoted the increase in these inflammatory diseases. They are there at the scene of the crime,” says Gewirtz, who hopes to investigate the link in humans.