New clinical research indicates that a widely used food additive, carboxymethylcellulose, alters the intestinal environment of healthy persons, perturbing levels of beneficial bacteria and nutrients. These findings were published in GastroenterologyThese results demonstrate the need to further investigate the long-term health effects of this food additive.
A team of scientists from Georgia State University’s Institute for Biomedical Sciences and INSERM (France), led the research. Researchers at Penn State University (USA) and Max Planck Institute Germany (Germany) also contributed to the research.
Carboxymethylcellulose (CMC) is a synthetic member of a widely used class of food additives, termed emulsifiers, which are added to many processed foods to enhance texture and promote shelf life. Although CMC has not been extensively studied in humans, it has been used in processed foods increasingly since the 1960s. CMC has been believed to be safe to ingest since it is eliminated from the feces and not absorbed. Scientists are questioning this assumption due to the increasing awareness of the health benefits provided in part by bacteria that lives in the colon and would interact with non-absorbed additives. CMC, along with other emulsifiers, caused severe intestinal disease in mice. This led to a wide range of chronic inflammatory conditions such as colitis, metabolic syndrome, colon cancer, and even death. However, human applications of these results have not been explored.
The team conducted a controlled-feeding study on healthy volunteers. Participants, housed at the study site, consumed an additive-free diet or an identical diet supplemented with carboxymethylcellulose (CMC). The researchers focused on intestinal bacteria and metabolites, as the diseases CMC causes in mice can take years to manifest in humans. CMC consumption had a significant impact on the colon’s bacteria composition, with a reduction in certain species. CMC-treated patients also showed a dramatic decrease in beneficial metabolites, which are believed to be essential for maintaining a healthy colon.
Finally, researchers performed colonoscopies at the beginning of and end of the study on subjects who had consumed CMC. They discovered that some subjects had gut bacteria that was encroaching into their mucus. This is a characteristic of type 2 diabetes and inflammatory bowel disorders. While CMC did not cause any disease in this two-week study per se, the results from the animal studies support the conclusion that long-term CMC intake might lead to chronic inflammatory diseases. Further studies are needed to determine the effects of this additive.
Dr. Andrew Gewirtz from Georgia State University, one of the paper’s senior authors, stated that “it certainly disproves [the ‘it just passes though’ argument used to justify a lack of clinical research on additives].” Beyond supporting the need for further study of carboxymethylcellulose, the study “provides a general blueprint to carefully test individual food additives in humans in a well-controlled manner,” said co-senior author Dr. James Lewis, of the University of Pennsylvania, where the subjects were enrolled.
Dr. Benoit Chassaing (research director at INSERM University of Paris, France), was the lead author. He noted that such studies must be large enough to account high levels of subject heterogeneity. Chassaing stated that our results indicate that CMC and other food additives responses are highly personalized. Therefore, we are currently developing approaches to predict which individuals might be sensitive.
This study was supported by the National Institutes of Health (NIH), the European Research Council (ERC), the Max Planck Society (MPS), the INSERM, and the Kenneth Rainin Foundation.