- Researchers report that high-fat diets may alter the gut microbe and increase the risk of colorectal cancer.
- They say a study involving mice indicated that high-fat diets can cause changes in the gut bacteria and alter digestive molecules known as bile acids.
- Experts say you can reduce your risk of colorectal cancer by adopting healthy dietary practices and limiting foods high in fat content.
Obesity is a known risk factor for colorectal cancer and new research indicates that a high-fat diet can trigger changes in the digestive system that can increase inflammation and raise the prevalence of this type of cancer.
The study, which was published in the journal Cell Reports, suggests that switching to a low-fat diet can help prevent colorectal cancer.
It also identifies a key protein in the gut that could be targeted in anti-cancer therapies.
“This provides a more detailed explanation of how the gut microbiome may be altered resulting in an increase in inflammation, which is one of current explanations for the development and progression of colorectal cancer,” Dr. Anton Bilchik, the chief of medicine and the director of the gastrointestinal and hepatobiliary program at Providence Saint John’s Health Center in California, told Medical News Today.
Details from the study on high-fat diets and colorectal cancer
In their study, researchers at the Salk Institute and the University of California San Diego fed lab mice with a genetic predisposition to colorectal cancer a high-fat diet.
They tracked changes in their gut bacteria and altered digestive molecules called bile acids, which are produced by the liver and help digest food and absorb cholesterol, fats, and nutrients.
The study authors reported that a fatty diet increased the levels of certain gut bacteria that, in turn, altered bile acids in a way that increased inflammation and inhibited the replenishment of intestinal stem cells, which help to repair cellular damage in the body.
Those changes can raise the risk of colorectal cancer, according to Ronald Evans, a senior study author and the director of Salk’s Gene Expression Laboratory, and his colleagues.
“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 in a press statement. “By knowing what the problem is, we have a much better idea of how to prevent and reverse it.”
The link between bile acids and colorectal cancer
In a 2019 study, a research group led by Evans reported that an increase in bile acids shut down a protein in the gut called the farnesoid X receptor (FXR), which is involved in lipid and energy metabolism and reducing inflammation.
The new study showed that the changes in bile acids also affected the proliferation of stem cells in the intestines.
Stem cells that replenish more slowly may mutate and encourage the growth of colorectal cancers, which often arise from stem cells, the paper noted.
Two types of gut bacteria shown to affect bile acids, Ileibacterium valens and Ruminococcus gnavus, were much more prevalent in the guts of mice on high-fat diets, the researchers reported.
How a high-fat increases cancer risks
A high-fat diet seemed to have a more profound effect on the gut microbiome and bile acids than the genetic mutation that made the mice more susceptible to colorectal cancer, the researchers said.
“We’ve known that a high fat diet, along with a diet high in red meat, tends to increase the risk of colon polyp formation and colon cancer,” Dr. Jesse P. Houghton, a senior medical director of gastroenterology at the Southern Ohio Medical Center, told Medical News Today.
“However, this new research links the high fat diet with a detrimental change in the composition of the gut microbiome, leading to an increase in inflammatory bile acids, which in turn leads to a downregulation in the FXR receptor,” he added. “This research elegantly connects the dots in previously known risk factors for colorectal cancer, providing a road map detailing how we go from macronutrients to molecular changes.”
How to reduce colorectal cancer risk
Evans and colleagues suggested that the FXR receptor could be targeted for future interventions to prevent colorectal cancer.
Bilchik said that while human clinical studies are still needed to confirm the study findings and possibly develop new treatments, “up to 70 percent of colorectal cancer is preventable through a healthy lifestyle, exercise and a balanced diet.”
Another study published today in the journal JAMA Network Open suggested that taking vitamin D supplements could help reduce the risk of relapse or death in a specific subset of digestive cancers, including colorectal cancer.
“Being at a normal weight and taking vitamin D improves your ability to survive cancer. Other factors include the patient’s genetic makeup and how the patient utilizes and breaks down vitamin D,” wrote Dr. Michael F. Holick, a professor of medicine, pharmacology, physiology and biophysics as well as a molecular medicine at Boston University’s Chobanian & Avedisian School of Medicine.
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