New grant to explore Mediterranean diet and its effect on colorectal cancer in African Americans

Can a change to a Mediterranean diet reduce the incidence of colorectal cancer in African Americans? Researchers at the University of Illinois Chicago have received a grant from the National Cancer Institute to find out.

“We believe colorectal cancer is more widespread in the African American population due to their higher prevalence of obesity, as their diets are often low in fiber and high in animal protein and saturated fats,” said Marian Fitzgibbon, PhD, professor at the University of Illinois College of Medicine and principal investigator on the grant. “The diets produce a higher abundance of proinflammatory gut bacteria, which in turn promotes tumors.”

Prior research suggests obesity and diet are key modifiable risk factors that contribute significantly to colorectal cancer. Obesity and diets low in fiber and high in animal protein and saturated fat are linked to elevated circulating and fecal bile acids and a shift in bile acid amino acid conjugation from glycine to taurine.

“This shift can foster conditions that allow certain gut microbes to grow and metabolize taurine-conjugated bile acids to genotoxic hydrogen sulfide and deoxycholic acid, microbial metabolites implicated in colorectal carcinogenesis,” said co-principal investigator Lisa Tussing-Humphreys, MS, RD, PhD, associate professor of kinesiology and nutrition at UIC, who also serves as co-leader of the University of Illinois Cancer Center’s Cancer Prevention and Control program.

Fitzgibbon, Tussing-Humphreys and their multidisciplinary research team believe targeting the bile acid-gut microbiome axis through lifestyle intervention to suppress the growth and metabolic activity of certain gut microbes may prevent colorectal cancer.  

Two hundred obese African Americans between the ages of 45 and 75 will be recruited to complete one of four interventions over an eight-month period: maintaining a stable weight eating strictly a Mediterranean diet; losing weight by restricting calories with no change in diet; losing weight through a Mediterranean diet; and control measurements.

A Mediterranean diet, inspired by the eating habits of Spain, Italy and Greece, is typically high in vegetables, fruits, whole grains, beans, nuts and seeds, and olive oil. It normally has a low intake of meats and dairy foods.

This is the first study to conduct a random clinical trial to compare these four interventions, said Fitzgibbon, who also serves as associate director of the Population Sciences program at the University of Illinois Cancer Center.

“We believe our research will reveal critical information on how weight loss and diet can address colorectal cancer risk not only in African Americans but also in other high-risk populations,” she said.

Excluding skin cancers, colorectal cancer is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that 104,270 new colon cancer cases will be diagnosed in 2021, and 45,230 new cases of rectal cancer.

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