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Randomized controlled-feeding study of dietary emulsifier carboxymethylcellulose reveals detrimental impacts on the gut microbiota and metabolome

Chassaing B, Compher C, Bonhomme B, Liu Q, Tian Y, Walters W, Nessel L, Delaroque C, Hao F, Gershuni V, Chau L, Ni J, Bewtra M, Albenberg L, Bretin A, McKeever L, Ley RE, Patterson AD, Wu GD, Gewirtz AT, Lewis JD. (2021) Gastroenterology   Nov 10;S0016-5085(21)03728-8. doi: 10.1053/j.gastro.2021.11.006. Online ahead of print. 

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Background & aims: 

Epidemiologic and murine studies suggest that dietary emulsifiers promote development of diseases associated with microbiota dysbiosis. While the detrimental impact of these compounds on the intestinal microbiota and intestinal health have been demonstrated in animal and in vitro models, impact of these food additives in healthy humans remains poorly characterized.


To examine this notion in humans, we performed a double-blind controlled-feeding study of the ubiquitous synthetic emulsifier carboxymethylcellulose (CMC) in which healthy adults consumed only emulsifier-free diets (n=9) or an identical diet enriched with 15 grams per day of CMC (n=7) for 11 days.


Relative to control subjects, CMC consumption modestly increased postprandial abdominal discomfort and perturbed gut microbiota composition in a way that reduced its diversity. Moreover, CMC-fed subjects exhibited changes in the fecal metabolome, particularly reductions in short-chain fatty acids and free amino acids. Furthermore, we identified 2 subjects consuming CMC who exhibited increased microbiota encroachment into the normally sterile inner mucus layer, a central feature of gut inflammation, as well as stark alterations in microbiota composition.


These results support the notion that the broad use of CMC in processed foods may be contributing to increased prevalence of an array of chronic inflammatory diseases by altering the gut microbiome and metabolome.

Keywords: Emulsifier; Metabolism; Metabolome; Microbiota.


This human clinical trial showed that just 2 weeks of consuming a diet containing a widely-used synthetic food additive vs a control diet without this led to increased gut and digestive symptoms (consistent with 'indigestion'), and significant changes in the gut microbiota of healthy adults.

Furthermore, two of the nine participants consuming the additive showed marked gut microbial changes, consistent with those seen in inflammatory bowel diseases.

The findings support those of previous studies in animals, showing that consumption of this artificial additive - the emulsifier carboxymethylcellulose (CMC) - causes gut inflammation and disrupts gut microbial balance, promoting both inflammatory bowel disorders and metabolic syndrome, a precursor to Type 2 diabetes and cardovascular disease.

This food additive is extensively used in a wide range of ultra-processed food products, having been classified as safe long ago in the 1960s (on the grounds that most of it is simply excreted), i.e. decades before the fundamental importance of the gut microbiome for almost every aspect of human health was recognised. 

However, these latest findings in a human clinical trial suggest that an urgent review of its safety is now needed, and public health warnings if not regulations on its use seem warranted.

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