Dietary emulsifiers are widely used in the modern food supply. They’re found in a variety of products, including ice cream, baked goods, and salad dressings. These additives help stabilize oil-water mixtures and extend the shelf life of foods. However, there are some concerns that emulsifiers could be harmful to human health.

These fears stem from the results of some animal and in vitro studies that examined the potential effect of emulsifiers on gut health. Because emulsifiers act as surfactants, they may disrupt the protective mucus layer that lines the gut, which potentially increases the risk of digestive diseases like inflammatory bowel disease. One in vitro study found that CMC can make mucus thicker and more dense, which can trap bacteria and other pathogens, whereas P-80 may thin out certain parts of the mucus, which allows bacteria to move through it quickly.^[1] Another study in mice found that consuming 2% of CMC in drinking water for 3 weeks led to increased intestinal inflammation, bacterial overgrowth, and bacteria adhering to and penetrating deep into the intestinal lining.^[2] However, human evidence of these effects has been limited.

The most notable aspect of the summarized study is the observed effect of emulsifiers on fecal short-chain fatty acids. These molecules support intestinal health by providing energy for gut cells, exerting anti-inflammatory effects, and helping to maintain the intestinal barrier. At week 6, the CMC group had significantly lower levels of acetate and butyrate, compared to the placebo group, whereas the P-80 group had lower levels of propionate. Critically, more advanced analyses confirmed that these differences persisted even after accounting for fiber and intake of other macronutrients, which suggests that emulsifiers impaired short-chain fatty acid production from bacteria rather than only reflecting dietary differences.

Whether these reductions in short-chain fatty acids result in disease or other health problems is still unclear. A recent large observational study from the French NutrtiNet-Santé cohort did find an association between emulsifier intake and an increased risk of cancer, cardiovascular disease, and type 2 diabetes.^[3]^[4]^[5] The reduced production of short-chain fatty acids in the summarized study and the observational research could align with the proposed mechanisms that emulsifiers may promote chronic inflammation and increase the risk of diseases over time.

However, there are some gaps in connecting these dots. Most importantly, the summarized study found no inflammatory changes, which raises fundamental questions about whether the short-chain fatty acid reductions may actually translate into clinical consequences or may only manifest after years of exposure.

This trial does provide an important piece of evidence: at commonly consumed doses in humans, some emulsifiers can suppress short-chain fatty acid production, and this effect appears independent of overall dietary patterns. However, it’s not clear whether this suppression makes a clinical difference and leads to inflammation, disease, or adverse health outcomes. Longer-term experimental research in diverse populations, including people with existing metabolic or inflammatory conditions (in whom the effects might be more pronounced), is needed. For now, the evidence suggests that caution may be warranted, particularly for people with digestive conditions, but definitive dietary recommendations require further research.

Are emulsifiers bad for gut health? Original paper