A study conducted by scientists from the Pasteur Institute and Inserm has found that the consumption of food emulsifiers by mice during pregnancy and lactation can negatively impact the gut microbiota of their offspring. These early changes in the composition of gut bacteria are linked to a higher risk of developing chronic inflammatory bowel diseases and obesity later in life. The findings highlight the potential long-term health consequences that may be passed down through generations and emphasize the need for similar studies in humans to assess the long-term effects of emulsifiers on health. The research was published in the journal Nature Communications.

What are emulsifiers and where are they found?

Emulsifiers are food additives widely used in processed foods to improve texture and extend shelf life. They are commonly found in dairy products, baked goods, ice cream, and certain types of powdered infant formulas. Despite their widespread use, the impact of these substances on human health—especially on the gut microbiota—remains insufficiently studied.

The course of the experiment

Under the guidance of Benoit Chassaing, Inserm research director and head of the Host-Microbiota Interactions Laboratory, female mice were given two common emulsifiers—carboxymethylcellulose (E466) and polysorbate 80 (E433). The additives were administered for ten weeks before pregnancy and throughout pregnancy and lactation. The offspring of these mice never received emulsifiers directly, but scientists studied their gut microbiota.

The results showed that even in the first weeks of life, young mice exhibited significant changes in the composition of their gut bacteria. This period is especially important, as mothers naturally transfer part of their microbiota to their offspring through close contact.

Changes in microbiota and their consequences

The offspring showed an increase in the number of flagellated bacteria, which are known to activate the immune system and trigger inflammation. It was also observed that more bacteria were found closer to the intestinal mucosa. This process, known as bacterial “encroachment,” led to the premature closure of certain pathways in the gut that normally allow small bacterial fragments to pass through the mucus layer, helping the immune system learn to tolerate its own microbiota.

When these pathways closed too early, the connection between the gut microbiota and the immune system was disrupted. As the animals matured, this led to excessive immune activity and chronic inflammation, significantly increasing the risk of inflammatory bowel diseases and obesity. Thus, the study links early microbiota changes in mice—even without direct emulsifier consumption—to a higher likelihood of developing chronic diseases in the future.

Implications for future generations

“It is extremely important to better understand how our diet can affect the health of future generations. These results underscore the importance of regulating the use of food additives, especially in powdered infant formulas, which often contain such substances and are consumed during a critical period of microbiota development,” notes Benoit Chassaing. The researchers plan to continue their work with clinical trials to study the transmission of microbiota from mother to child—both with and without maternal consumption of food additives, as well as the direct effects of these substances on infants through baby formulas.

The study was supported by grants from the European Research Council (ERC).