The microbiota, an ally for predicting individual sensitivity to food additives

Widely used by the food industry, emulsifiers – a type of food additive – are found in many daily foods (sliced bread, ice creams, crème fraîche, plant milks, etc.). Given their omnipresence in our diet, the health effects of their consumption have become a real public health issue. Benoit Chassaing, Inserm Research Director and leader of the Microbiome-Host Interactions team at Institut Pasteur (Inserm/Université Paris Cité/CNRS), has previously reported that by acting directly on our gut microbiota, these additives could promote the development of chronic inflammatory diseases and metabolic deregulations. In a new study published in Gut, he and his team developed a human microbiota modelling system capable of predicting each person's sensitivity to an emulsifier, using a simple stool sample. This discovery paves the way for a personalised nutrition approach based on the gut microbiota in order to maintain good gut and metabolic health.

The food industry is making increasing use of many additives to improve the texture and extend the shelf life of its products. Several studies have reported their harmful effects on gut and metabolic health, linked to their interactions with our microbiota. In 2015, Inserm Research Director Benoit Chassaing looked at the effects on the microbiota and gut health of consuming an emulsifier, carboxymethylcellulose (CMC), commonly found in industrial brioches [sweet buns], sliced bread and ice creams[1]. The results of his research suggested that consuming this additive over the long term could have a negative impact on the microbiota and, as a consequence, promote chronic inflammatory diseases and metabolic deregulations.

Then, during a clinical trial on healthy volunteers, Chassaing and his team were able to report that we are not all equal when it comes to emulsifiers. Some people, deemed to be emulsifier-sensitive, have a microbiota that is highly reactive to them, whereas others appear to have a microbiota that is completely resistant to their negative effects. Given the omnipresence of this class of food additives in our modern diet, it has become necessary to better understand these variations in sensitivity between individuals, in order to promote better gut and metabolic health.

With this goal in mind, Chassaing’s team has succeeded in predicting a given person’s sensitivity to an emulsifier, by performing an in-depth analysis of their microbiota.

To do this, the researchers developed a laboratory microbiota modelling system capable of reproducing the human microbiota. This model enabled the researchers to test the effect of CMC on different microbiotas in vitro, leading to the observation that a given microbiota can either be sensitive or resistant to CMC. In addition, it was possible to perfectly validate the predicted sensitivity of a given microbiota thanks to microbiota transfer approaches in a mouse model, with the observation that only those microbiotas predicted to be sensitive to emulsifiers were in fact able to lead to severe colitis in animals consuming CMC.

Using stool samples, the researchers then identified a specific metagenomic signature (analysis of the bacterial DNA contained in intestinal microbiota) of  sensitivity to CMC, making it possible to predict perfectly, by means of simple molecular analyses, whether a given microbiota is sensitive or resistant to this emulsifier.

'These discoveries could be used in the near future to determine someone’s sensitivity to emulsifiers, in order to offer everyone a suitable nutritional programme, explains Chassaing, leader of an Inserm research team at Institut Pasteur and last author of the study.

'Detecting this sensitivity in healthy people could also help prevent the onset of various intestinal disorders – and in patients, prevent the progression of the disease and/or reduce its symptoms.'

The scientists will now use a much larger cohort of patients with Crohn’s disease to validate these predictive approaches of emulsifier sensitivity. They will also now try to explain the molecular reasons for this sensitivity to emulsifiers, and identify approaches aimed at beneficially manipulate the intestinal microbiota to protect against emulsifier-mediated inflammation.

[1]On processed products, CMC is also referred to as E466.