What’s good for keeping food products stable and safe on the shelf may not be healthy for the body. Researchers report in the journal Cancer Research that emulsifiers create the ideal conditions for triggering colon cancer in mice.

Emulsifiers are chemicals—in some cases detergents, actually—added to blend oily and water-based ingredients in processed foods and to keep them consistently mixed so they don’t separate. Processed foods often contain several of them; food regulations limit the amount of each emulsifier present in a particular food product to 1% to 2%, but they don’t restrict the number of emulsifiers allowed. Emilie Viennois from the Institute of Biomedical Sciences at Georgia State University, who led the new research, showed in earlier work that emulsifiers changed the good bacteria living in the guts of mice. These changes promoted metabolic syndrome, which is a risk factor for certain chronic diseases such as diabetes, obesity and heart disease, and inflammation; those in turn have been connected to inflammatory bowel disease (IBD). Some cases of IBD can trigger tumors to grow.

In her latest study, Viennois wanted to connect the dots to focus on whether emulsifiers affected cancer risk: specifically colon cancer. After three months of feeding some animals two common ones—polysorbate 80 and carboxymethylcellulose—in their water, she found that animals who consumed emulsifiers showed changes in their gut microbes that were consistent with promoting tumor growth. Using a theoretical model for conditions that promote colon cancer, she found that the higher levels of inflammation created by the microbial changes form the perfect cancer friendly environment.

“We think that can create a niche for tumor development,” she says.

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Whether the same thing happens in people to increase their colon cancer risk isn’t clear. But Viennois notes that most processed foods contain several different types of emulsifiers, and in her study, she only tested two emulsifiers in the mice. She is continuing her work to better understand the role that emulsifiers play in tumor growth in the animals, and is also collaborating with other groups to research the connection in people. She plans to look at things such as the gut bacteria populations and how they change, as well as body weight and blood levels of cancer and metabolic markers.

For now, however, “I would tell people to try to cook instead of using food industry products,” she says, since many processed foods contain emulsifiers. “In meals, mix processed foods with some homemade food so you don’t have huge exposure to emulsifiers in one meal.”

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