Researchers have uncovered that the regular consumption of navy beans may help modulate markers linked to obesity and disease and improve the gut microbiome in colorectal cancer survivors, according to a novel study published by Zhang et al in eBioMedicine.
Background
Obesity, poor diet, and gastrointestinal issues can all cause disturbances in an individual’s typical microbial balance. For patients and survivors of colorectal cancer, these disturbances may result in inflammation and can adversely impact survival. Even after cancer treatment or precancerous polyp removal, a poor diet and an unbalanced gut microbiome can have negative effects on prevention efforts for both cardiovascular disease and additional cancer types. Conversely, a healthy gut microbiome may be associated with cancer prevention and positive treatment outcomes.
Beans, particularly small white navy beans, contain gut-supporting fibers, amino acids, and other nutrients that can help proliferate beneficial bacteria in the colon, support immune health, and regulate inflammation. Despite being accessible and cost-effective, navy beans are frequently avoided by U.S. individuals as a result of their potential to cause mild or acute gastrointestinal side effects—which can be mitigated with proper preparation and consistent consumption.
Study Methods and Results
In the new BE GONE trial, the researchers randomly assigned 48 patients over the age of 30 years who met the criteria for obesity via body mass index or waist size and had a history of bowel lesions—including colorectal cancer and/or high-risk precancerous colorectal polyps detected at colonoscopy—to incorporate 1 cup of organic, canned, pressure-cooked white navy beans into their diets or follow a regular diet for 8 weeks.
The patients were also given the choice to prepare their own meals, with close follow-up and counseling from a dietitian. Every 4 weeks, the patients who participated in the trial were asked to provide stool and fasting blood samples to assess shifts in their gut microbiomes as well as the host metabolites and markers. The researchers considered the patients adherent if they consumed at least 80% of the beans over the intervention period and followed the prescribed regimen for at least 5 days per week.
The researchers found that the patients who added 1 cup of navy beans to their diets daily saw positive changes in their gut microbiome, including increases in microbial alpha diversity—such as Faecalibacterium, Eubacterium, and Bifidobacterium—and decreases in pathogenic bacteria.
“Observing a shift in microbiome diversity with diet intervention alone is rare, and this study underscores the ability of a readily available prebiotic food to bring about such changes,” explained senior study author Carrie Daniel-MacDougall, PhD, MPH, Associate Professor of Epidemiology at The University of Texas MD Anderson Cancer Center. “Over the course of 8 weeks, there was an improvement in [patients’] gut health, marked by an increase in beneficial bacteria, which wards off the harmful bacteria,” she added.
The limitations of the trial included patient aversion to continually consuming navy beans. The researchers described no serious side effects among the patients.
Conclusions
The results of the new trial underlined the significance of the therapeutic role of naturally prebiotic-rich foods, while further emphasizing the need for consistent and sustainable dietary adjustments for high-risk patients with cancer.
“The beans did not appear to induce gut inflammation or seriously impact bowel habits, which is crucial for [patients and survivors of colorectal cancer],” underscored Dr. Daniel-MacDougall. “However, once [patients] stopped eating the beans, the positive effects faded quickly, highlighting the need to educate patients on how to maintain healthy habits,” she suggested.
The researchers plan to focus on a wider variety of prebiotic foods and how changes to the gut microbiome may affect patients undergoing immunotherapy. They concluded that further studies may be needed to determine how dietary interventions can be utilized to reduce cancer risk and improve treatment outcomes.
The researchers cautioned that patients should consult their physicians prior to initiating the navy bean diet, since it could have negative impacts without proper guidance.
Disclosure: The research in this trial was funded by the American Cancer Society, with initial support from an MD Anderson Institutional Research Grant, as well as the National Cancer Institute, the Andrew Sabin Family Fellowship Program, the Cancer Prevention and Research Institute of Texas, and The University of Texas MD Anderson Cancer Center Moon Shots Program. The navy beans used in the study were independently purchased with funds from the Dry Bean Health Research Program. For full disclosures of the study authors, visit thelancet.com.
