Study: Common food additive found to disturb beneficial bacteria in the gut

By Mary Ellen Shoup

- Last updated on GMT

Photo Credit: GettyImages / MARHARYTA MARKO
Photo Credit: GettyImages / MARHARYTA MARKO

Related tags microbiota Food additives

Carboxymethylcellulose, a widely-used emulsifying and thickening food additive ingredient, can alter the intestinal environment of gut microbiome, disturbing levels of beneficial bacteria, suggests new clinical research.

The research, published in Gastroenterology​,​ was led by a team of scientists from Georgia State University's Institute for Biomedical Sciences, INSERM (France) and the University of Pennsylvania. Key contributions also came from researchers at Penn State University and Max Planck Institute (Germany).

Carboxymethylcellulose (CMC) is a common food additive which has been used in processed foods since the 1960s. According to, it functions as a thickening, suspending, emulsifying, stabilizing, and film-forming agent in many food items including beverages, bakery, dairy, dessert products and meat products. 

However, its long-term health impacts on humans have not been studied, argued researchers who cited previous experiments on mice which found that CMC, and some other emulsifiers, altered gut bacteria resulting in a range of chronic inflammatory conditions, including colitis, metabolic syndrome, and colon cancer.

"It had long been assumed that CMC was safe to ingest because it is eliminated in the feces without being absorbed. However, increasing appreciation of the health benefits provided by bacteria that normally live in the colon, and thus would interact with non-absorbed additives, has led scientists to challenge this assumption,"​ noted researchers of the study.

Study methods and conclusions

To study the food additive's impact on humans' gut microbiome, researchers performed a randomized controlled-feeding study among healthy volunteers at the University of Pennsylvania who were given either an additive-free diet or an identical diet supplemented with CMC for a two-week period.

Researchers focused on the levels of intestinal bacteria and metabolites by performing colonoscopies on subjects at the beginning and end of the study.

They noticed that a subset of subjects consuming CMC displayed gut bacteria encroaching into the mucus, which has previously been observed to be a feature of inflammatory bowel diseases and type 2 diabetes. 

"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 62 reductions in short-chain fatty acids and free amino acids,"​ wrote researchers in the study. 

While the two-week study did not result in any disease, the results did support researchers' conclusions that long-term consumption of the food additive might promote chronic inflammatory diseases in humans.

"It certainly disproves the 'it just passes through' argument used to justify the lack of clinical study on additives​," said senior author of the study, Dr. Andrew Gewirtz of Georgia State University.

Researchers also agreed that while further study of carboxymethylcellulose is needed to draw definitive conclusions on its impact on human health, the study "provides a general blueprint to carefully test individual food additives in humans in a well-controlled manner,​" added co-senior author Dr. James Lewis, of the University of Pennsylvania.

Lead author Dr. Benoit Chassaing, research director at INSERM, University of Paris, France, noted the need for large studies to be performed with a larger pool of participants. "Indeed, our results suggest that responses to CMC and likely other food additives are highly personalized, and we are now designing approaches to predict which individuals might be sensitive to specific additives,​" Chassaing said.

Source:​ Gastroenterology

Ubiquitous food additive alters human microbiota and intestinal environment.

Authors:: Chassaing B, et al. 

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