Humans have a habit of playing with their food, which is evident from the steady increase in food additives in packaged produce we have witnessed in the past half-century. Food scientists chuck in these extra ingredients for a variety of reasons, such as to improve texture and flavor, or to make a product last longer or look more appealing. Perfectly whipped ice-creams and velvety smooth chocolate bars are both possible thanks to emulsifiers, for example, which are substances that help different things mix together when they ordinarily wouldn’t.
Although studies have indicated that emulsifiers are safe, new research suggests that these tests may have been inadequate with the discovery that they can alter the delicate composition of microbes in the gut. Not only that, but these additives were found to trigger intestinal inflammation in rodents and increase the risk of inflammatory bowel disease and a cluster of obesity-related conditions collectively known as metabolic syndrome. Although the researchers have yet to prove whether the same thing is happening in humans, they propose that these ingredients may have contributed to the observed increase in these diseases since the mid-20th century. The study has been published in Nature.
The intestinal tract is home to a diverse and vast collection of microbes known as the gut microbiota. Far from being unwelcome guests, these bugs bestow a variety of benefits to the host, such as assisting in the production of hormones and vitamins. While we need these microbes to stay healthy, we don’t want them to get too close to our delicate intestinal lining. That’s because they can arouse the immune system and trigger inflammation, and if this inflammation isn’t controlled, it can lead to things like inflammatory bowel disease and maybe even metabolic syndrome—a group of conditions that raise the risk of heart disease and diabetes.
To prevent this from happening, our gut is lined with mucus that keeps the microbes at a safe distance. Things that disturb the interactions between gut bacteria and this protective mucus may therefore have the potential to promote the onset of diseases associated with chronic gut inflammation. Since emulsifiers are detergent-like molecules that have been shown to increase the movement of bacteria across sheets of cells in the lab, scientists wondered whether they could also be promoting inflammation and therefore inflammatory bowel disease.
To explore this idea, scientists added two commonly used emulsifiers to the diet of mice at concentrations comparable to what would be found in processed foods. Soon enough, their guts became inflamed and they showed tell-tale signs of metabolic syndrome, such as obesity and increased blood sugar levels. Further investigation revealed that alongside these symptoms, their gut microbiota composition had significantly changed. Not only was there an increase in species that are renowned for triggering inflammation and being able to digest and burrow through mucus, but there was also a decrease in the presence of anti-inflammatory species. Interestingly, the metabolic syndrome-like symptoms were not experienced in mice bred to be germ-free, but these animals quickly developed these problems when transplanted with feces from emulsifier-fed mice.
Of course, these findings may not translate to humans, which is why the researchers plan to take this work further and attempt to find out whether or how they are affecting our gut microbiome, which could have implications for the obesity epidemic.