Food emulsifiers linked to metabolic syndrome and gut flora disturbance
Emulsifiers used in many processed foods may increase the risk of inflammatory bowel diseases and metabolic disorders, according to findings in a mouse study from Georgia State University in Atlanta.
The study, published 25 February 2015 in the journal Nature, found that in mice, chemicals known as emulsifiers were found to alter the make-up of bacteria in the colon. This is the first time that these additives have been shown to affect health directly.
About 15 different emulsifiers are commonly used in processed Western foods for purposes such as smoothing the texture of ice cream and preventing mayonnaise from separating. Regulatory agencies such as the US Food and Drug Administration (FDA) rule that emulsifiers are “generally regarded as safe”, because there is no evidence that they increase the risk of cancer or have toxic effects in mammals.
However, when immunologist Professor Andrew Gewirtz at Georgia State University in Atlanta and his colleagues fed common emulsifiers carboxymethylcellulose and polysorbate-80 to mice, they found evidence that the chemicals affected the animals’ health.
Although the animals’ diet was not otherwise changed, healthy mice whose water contained the chemicals became obese and developed metabolic problems such as glucose intolerance. In mice genetically engineered to be prone to inflammatory gut diseases, emulsifiers also seemed to increase the severity and frequency with which the animals developed inflammatory bowel disease.
The most severe health effects were seen in mice that consumed the chemicals at a level similar to a person whose diet consists of only ice cream, according to Professor Gewirtz. However, the researchers said they saw effects even at one-tenth of the concentration of emulsifiers that the FDA allows in a food product.
To understand why emulsifiers affected the health of mice, researchers analysed bacteria from the animals’ colons. They found less diversity in the microbial species than in healthy mice, and found evidence that the microbes had migrated closer the cells lining the gut. Professor Gewirtz said he and his colleagues suspected that the emulsifiers could break down the heavy mucus that lines the mammalian gut and prevents bacteria from coming into contact with gut cells. If this happens, the bacteria cause inflammation in the gut, which can also lead to changes in metabolism.
Professor Gewirtz says that previous studies may have missed these links because newly developed food additives are tested in large swathes of the population, masking any subtle effects in people whose genetics or gut-microbe composition predispose them to these diseases. Professor Gewirtz said “the idea that a subset of the population may be sensitive isn’t on the radar” for regulators.
The researchers said they hoped to incorporate consumption of emulsifiers, sweeteners and other artificial additives into their study, but caution that there were “many components to inflammatory and metabolic diseases”.
Professor Gewirtz said that many more human and animal studies need to be completed before regulatory agencies would consider changing how additives are approved. The researchers hope to complete a study in humans soon.
‘Exaggerated’ reports criticised by experts
However, reporting of the study has been criticised by some experts, saying the Georgia State University study in mice indicated further study was needed in humans, but that saying emulsifiers caused obesity in humans was “jumping to conclusions”.
Fred Brouns, from Brouns Health Food Consulting in the Netherlands said such news streams “may not be of much help to inform consumers”.
“The real story tells us that a link has been found between the consumption of 2 types of emulsifiers (out of 15) and inflammation in the gut of mice, causing them to eat more,” Mr Brouns said.
“Yet, concluding that “eating emulsifiers cause overweight” is jumping to conclusions and misleading consumers,” Mr Brouns said.
He pointed out that the study was in mice and not in humans; effects were observed in 2 out of 15 types emulsifiers; that emulsifiers cause inflammation in humans has not been shown yet; that they might not cause inflammation in all individuals; that many non-processed- natural- foods contained emulsifiers; and that the human body produces emulsifiers to improve fat absorption in the small intestine.