Food additive alters gut bacteria to cause colorectal cancer

Of the cancers that affect both men and women, colorectal cancer is the third most common cancer in the United States and the second leading cause of cancer-related death. 

Emulsifiers, which are added to most processed foods to aid texture and extend shelf life, can alter intestinal bacteria in a manner that promotes intestinal inflammation and colorectal cancer, according to a new study.

There are over 100 trillion microorganisms living in the gut, including bacteria, viruses, and fungi. The microbiota is made of the physiological interaction between the host's microorganisms and the ones introduced from the environment.

The microbiota is acquired during the first stages of life and varies with every individual. Having a diverse and balanced microbiota is crucial in keeping a healthy immune system.

Severe changes in the microbiota, either as a result of changing one's diet, lifestyle, or because of an infection, can alter the symbiotic relationship between the host microorganisms and the environmental ones, leading to IBD.

IBD promotes the formation of tumors in the colon. Low-grade inflammation, which has been associated with changes in the microbiota and metabolic disease, has also been observed in many cases of colorectal cancer.

In the new study, the team fed mice the two most common additives have also been linked to low-grade bowel inflammation and metabolic disease: polysorbate 80 and carboxymethyl cellulose.

The doses were replicated so as to mirror the proportions these emulsifiers are commonly added to human processed food.

Not only did emulsifiers alter the microbiotic environment in a way that is pro-inflammatory, but it also changed the balance between cell proliferation and cell death, which enhances tumor development.

The negative effects of consuming emulsifiers disappeared completely in mice that had no germs and therefore no microbiota. Researchers also transplanted microbiota from mice that consumed emulsifiers to germ-free mice, and this was enough to change the balance in the intestine's epithelial cells.

This further reinforces the central role that the microbiota plays in tumor induction and development.

Lead researcher Dr Emilie Viennois said: 'The incidence of colorectal cancer has been markedly increasing since the mid-20th century.

'A key feature of this disease is the presence of an altered intestinal microbiota that creates a favourable niche for tumorigenesis.'

This study demonstrates that emulsifiers induce alterations in the microbiome. These alterations are both necessary and sufficient for changing the balance in the intestinal epithelial cells.

The US researchers are now testing to see what triggers the alteration and the exact way it can cause cancer.

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