Colorectal cancer rates among young adults are skyrocketing and researchers may have determined why. The new study found that high-fat diets can alter gut bacteria and increase the risk of colorectal cancer in mice. Experts say the same gut-altering mechanism caused by the typical Western, high-fat diet could apply to humans as well.

 According to CNN, the American Cancer Society reports that the proportion of colorectal cancer cases among adults younger than 55 increased from 11% in 1995 to a whopping 20% in 2019.

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While scientists said that the factors driving that rise remain a mystery, the new study, which was published in Cell Reports, found that high-fat diets may alter the gut bacteria and change digestive molecules known as bile acids. While the study was done in mice, experts say that we can reduce our risk of colorectal cancer by adopting healthy dietary practices and limiting foods high in fat content, says Medical News Today.

Researchers at the Salk Institute and the University of California San Diego fed a high-fat diet to mice with a genetic predisposition to colorectal cancer.  They tracked the changes in gut bacteria and bile acids, digestive molecules produced by the liver that help digest food and absorb cholesterol, fats, and other nutrients.

The study authors observed that a fatty diet boosted the levels of certain gut bacteria that, in turn, altered the bile acids, causing inflammation and inhibiting the replenishment of intestinal stem cells, which help to repair cellular damage in the body. Ronald Evans, director of Salk’s Gene Expression Laboratory, and a senior author of the study said that these changes may increase the risk for colorectal cancer.

“The balance of microbes in the gut is shaped by diet, and we are discovering how alterations in the gut microbial population can create problems that lead to cancer,” Evans said in a news release. “This paves the way toward interventions that decrease cancer risk.”

The new research builds on previous work conducted by Evans and his colleagues in 2019 that showed high-fat diets boosted overall bile levels. It showed that the modified bile acids affected the proliferation of stem cells of the intestines, which could lead to mutations and the growth of cancers.

“We’ve deconstructed why high-fat diets aren’t good for you, and identified specific strains of microbes that flare with high-fat diets,” said Evans. “By knowing what the problem is, we have a much better idea of how to prevent and reverse it.”

Experts say that while human clinical studies are still needed to confirm the study findings, up to 70% of colorectal cancer is preventable through a healthy lifestyle, exercise and balanced diet, according to research.