Food emulsifiers, gut bacteria and metabolic syndrome
What it found
Some common food emulsifiers changed gut bacteria and gut barrier measures in lab tests and animals, and one human trial found a high daily dose of carboxymethylcellulose caused abdominal discomfort and shifted gut bacteria.
Other emulsifiers, such as lecithins and acacia gum, showed signs of feeding beneficial bacteria.
What they found
Studies in people
Human trial with CMC
In a randomized controlled feeding study, healthy adults ate either an emulsifier-free diet or the same diet with 15 g of carboxymethylcellulose per day for 14 days. The CMC group had more postprandial abdominal discomfort and reduced gut bacteria richness and diversity, but fecal lipopolysaccharide and flagellin levels did not change.
Ultra-processed food and metabolic syndrome
A survey of 789 people aged 40 to 70 found a dose-response link between ultra-processed food consumption and metabolic syndrome. Higher intake was also linked to more severe liver disease markers in people with fatty liver.
Animal and lab studies
Gut bacteria shifts in lab tests
In lab models of the human gut, polysorbate 80, carrageenan and agar agar reduced Clostridiales and Verrucomicrobiales bacteria, including groups known for anti-inflammatory properties. Xanthan gum, sorbitan monostearate, glyceryl stearate and carrageenan raised bioactive lipopolysaccharide levels.
Emulsifiers and short-chain fatty acids
In lab tests with human fecal bacteria, carboxymethylcellulose, polysorbate 80, rhamnolipids and sophorolipids lowered bacterial diversity and shifted short-chain fatty acid profiles, with butyrate dropping by up to 96% compared to controls. Rhamnolipids and sophorolipids also increased pathogenic Escherichia/Shigella and Fusobacterium.
Animal studies on gut barrier
In mice and rats, carboxymethylcellulose and polysorbate 80 increased Proteobacteria and E. coli, reduced Bacteroides and Clostridia, raised circulating lipopolysaccharide, and changed the intestinal barrier. Carrageenan disrupted intercellular junctions in animal tissue.
Studies in people and animals
Emulsifiers with possible benefits
Acacia gum promoted Bifidobacteria and inhibited Clostridium histolyticum in lab tests. Lecithins increased butyrate-producing Clostridium leptum in mice. Glycerol monolaurate at high doses in mice improved metabolic markers, but at low doses caused inflammation and gut bacteria imbalance.
What the authors conclude
“There is some progress in understanding how some food emulsifiers could contribute to developing metabolic diseases through gut microbiota alterations while others could have prebiotic effects.”
Also in their conclusions
- They say that certain emulsifiers could contribute to metabolic and inflammatory diseases by shifting gut bacteria toward pro-inflammatory communities and altering the intestinal barrier.
- They note that other emulsifiers could have prebiotic effects, improving gut dysbiosis and metabolic disorders.
- They call for clarification on whether each person's gut bacteria profile affects how they respond to emulsifiers, and on the impact of cumulative intake and mixtures.
How it was done
Emulsifier use in processed foods has risen alongside metabolic syndrome in Western countries, but it was not clear whether emulsifiers affect metabolic disorders through gut bacteria. This made it hard for dietitians to give evidence-based advice on which emulsifiers and how much might matter.
The authors searched three databases up to October 2021 for studies on emulsifiers and gut bacteria, covering lab tests, animal studies and human studies. They also described where common emulsifiers are used in foods and what daily intake limits authorities have set.
What it can’t tell you
- Most of the evidence comes from lab tests and animals, which cannot show what happens in people.
- The human trial used a high dose of one emulsifier for 14 days, so it cannot show long-term effects or effects of typical daily intakes.
- The review cannot say how much emulsifier a person actually eats, because food labels do not list quantities.
Who paid
- Conflicts
- The authors declare no conflict of interest.
- Authors work at
- Fondazione Policlinico Universitario A. Gemelli IRCCS, Italy; Tuscia University, Italy; "Madonna del Soccorso" General Hospital, Italy
The paper
- Title
- Food Emulsifiers and Metabolic Syndrome: The Role of the Gut Microbiota
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- De Siena M, Raoul P, Costantini L, et al (2022). Food Emulsifiers and Metabolic Syndrome: The Role of the Gut Microbiota. Foods (Basel, Switzerland). doi:10.3390/foods11152205Free full textPubMed 35892789DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error