By Roberta Attanasio
“For centuries, additives have served useful functions in a variety of foods. Our ancestors used salt to preserve meats and fish, added herbs and spices to improve the flavor of foods, preserved fruit with sugar, and pickled cucumbers in a vinegar solution. Today, consumers demand and enjoy a food supply that is flavorful, nutritious, safe, convenient, colorful and affordable. Food additives and advances in technology help make that possible.” But, are food additives safe? Results from a recent study show that some food additives known as emulsifiers can alter the composition and location of the gut microbiota — the diverse population of 100 trillion bacteria that inhabit the intestinal tract — thus inducing intestinal inflammation. This inflammation, in turn, promotes the development of inflammatory bowel disease (Crohn’s disease and ulcerative colitis) and metabolic syndrome — disorders that are often severe and debilitating and afflict millions of people.
The ancient Greeks used the emulsifying power of beeswax in cosmetic products. Egg yolk was probably the first emulsifier ever used in food production back in the early 19th century. Emulsifiers are now added to bread, chocolate, ice cream, margarine, processed meat, and more. But why? Add oil to water and the two liquids will never mix. At least not until an emulsifier is added. Emulsifiers are molecules with one water-loving (hydrophilic) and one oil-loving (hydrophobic) end. They make it possible for water and oil to become finely dispersed in each other, creating a stable, homogenous, smooth emulsion.
The study results show that, in a mouse model, two common emulsifiers — caboxymethylcellulose (CMC) and polysorbate-80 (P80) — not only change the composition of the gut microbiota, they also make the gut more porous. The altered microbiota has enhanced capacity to digest and infiltrate the dense mucus layer that lines the intestine — bacteria reach immune cells, thus inducing activation of inflammatory pathways and the development of severe inflammation.
Such changes in bacteria trigger chronic colitis in mice genetically prone to this disorder, due to abnormal immune systems. In contrast, in mice with normal immune systems, emulsifiers induce low-grade or mild intestinal inflammation and metabolic syndrome, characterized by increased levels of food consumption, obesity, hyperglycemia and insulin resistance.
Fergus Shanahan (University College Cork), who was not involved in the study, told Ed Yong: “This work cannot be ignored.” He doubted that most people would be significantly affected by occasionally eating foods with emulsifiers — but risk might change for those who have a genetic predisposition to inflammatory bowel disease, or who eat lots of processed foods.
Andrew Gewirtz, senior author of the study, said in a press release: “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.”
Together, the researchers note that the current means of testing and approving food additives may not be adequate. Thus, we consume food containing chemicals that may promote diseases driven by low-grade inflammation or may cause disease in susceptible individuals.
Gewirtz told Ed Yong: ““We’re certainly eating less processed food since we’ve been doing this work. It took a lot of effort, but we did find one type of ice-cream in the supermarket that’s emulsifier-free.”
What about the U.S. Food and Drug Administration (FDA)? According to Ed Young, the FDA said in a statement: “The FDA closely monitors the scientific literature for information that might indicate a potential public health concern with a food substance. At this time, the FDA does not have sufficient evidence to alter its previous conclusion that polysorbate 80 and carboxymethyl cellulose are considered safe under their intended conditions of use in food.”