Emulsifiers, a common food additive, can alter intestinal bacteria to cause low-grade gut inflammation and promote colorectal cancer, new research shows.
The study, “Dietary emulsifier-induced low-grade inflammation promotes colon carcinogenesis,” was published in the journal Cancer Research.
Inflammatory bowel disease (IBD) carries an increased risk of colorectal cancer (CRC), a fact that gave rise to the concept of “colitis-associated cancer” and the notion that inflammation promotes colon tumor formation. A condition more common than IBD is low-grade inflammation, which correlates with altered gut microbiota — the vast population of microorganisms that inhabits the human intestine — and metabolic syndrome, both also present in many cases of CRC.
Researchers at Georgia State University’s Institute for Biomedical Sciences, working with mice, found that consumption of dietary emulsifiers (common additives to processed foods) may explain this association.
“The incidence of colorectal cancer has been markedly increasing since the mid-20th century,” Emilie Viennois, an assistant professor at the Institute and the study’s lead author, said in a news release. “A key feature of this disease is the presence of an altered intestinal microbiota that creates a favorable niche for tumorigenesis.”
“The dramatic increase in these diseases has occurred amidst constant human genetics, suggesting a pivotal role for an environmental factor,” added Benoit Chassaing, also an Institute assistant professor.
The researchers previously found that low-grade inflammation in the intestine can result from eating emulsifiers — additives that increase the shelf life and add texture to processed foods — because emulsifiers alter the composition of gut microbiota. Evidence has shown that emulsifiers in food promote the translocation of bacteria across epithelial cells, making it easier for bacteria to enter those gut cells. (Intestinal epithelial cells’ homeostasis, or equilibrium, is thought to govern tumor development.)
Using mice models of colitis-induced colon cancer, the researchers examined if emulsifiers could affect the gut microbiota in a way that also promoted colorectal cancer.
They found that regular consumption of two common emulsifiers (polysorbate 80 and carboxymethylcellulose) — fed to mice at doses that corresponded to those often found in processed foods — led to changes in intestinal bacteria that promoted inflammation in a way that could lead to cancer.
The changes in intestinal bacterial species caused bacteria to express more flagellin and lipopolysaccharide, which can activate pro-inflammatory gene expression by the immune system.
The researchers then conducted their experiments in an established mouse model of colon cancer. They found that consuming dietary emulsifiers was enough to make the mice more susceptible to colon tumors, because they helped to establish and maintain a pro-inflammatory environment that is associated with changes in the balance by which cells proliferate and die (apoptosis). A pro-tumor environment was also linked to altered, and potentially pro-inflammatory, intestinal microbiota.
“Overall, our findings support the concept that perturbations in host-microbiota interactions that cause low-grade gut inflammation can promote colon carcinogenesis,” the researchers concluded.
The team now plans to investigate which gut microbiota are responsible for such low-grade inflammation, and to understand the mechanism by which changes in gut microbiota lead to cancer.