Consuming frying oil may worsen colon inflammation and colon cancer, a study in mice suggests.
The study, “Thermally processed oil exaggerates colonic inflammation and colitis-associated colon tumorigenesis in mice,” was published in the journal Cancer Prevention Research.
From french fries to falafel, lots of foods are fried in vegetable oil. Consuming this oil may have health risks, but most studies done have focused on its effect in people who don’t have ongoing diseases in their guts. In this study, researchers set out to determine the effect of this oil consumption in mouse models of colon cancer and inflammatory bowel disease (IBD).
The researchers used consumption-grade oil commonly used in America, in which falafel had been fried. They added that oil to the food of some mice, while other mice were given food supplemented with oil that had not been used for frying.
“We tried to mimic the human being’s diet,” Jianan Zhang, a PhD student at UMass Amherst and co-author of the study, explained in a press release.
The researchers compared inflammation, colon tumor growth, and leakage of gut bacteria in both models, finding that eating the frying oil worsened all those conditions. For example, in the cancer model, “The tumors doubled in size from the control group to the study group,” said study co-author Guodong Zhang, who is a professor at UMass Amherst.
Since frying oil worsened these symptoms as compared to fresh oil — not no oil at all — the researchers hypothesized that chemical changes to the oil that occur during frying were responsible for the observed effects. Specifically, they guessed that polyunsaturated fatty acids that become oxidized, which happens when oil is heated, might be responsible.
To test this, the researchers isolated only the polar compounds in the frying oil (which includes the aforementioned fatty acids). Mice fed a diet supplemented with these compounds had results very similar to mice fed frying oil itself, suggesting the hypothesis holds some validity.
Importantly, these data suggest that eating fried food might make existing disease worse, not cause the disease in the first place: “It’s not our message that frying oil can cause cancer,” said Guodong Zhang. “If somebody has IBD or colon cancer and they eat this kind of food, there is a chance it will make the diseases more aggressive.”
“For individuals with or prone to inflammatory bowel disease,” Guodong Zhang added, “it’s probably a good idea to eat less fried food.”