by A new study i e-Medicine investigated the effect of incorporating canned navy beans into the regular diet for eight weeks.
This research focused on the impact of such dietary changes on the gut microbiota, as well as circulating markers and metabolites, in obese individuals with a history of colorectal neoplasia and precancerous polyps. The study also included participants who were taking medications such as statins or metformin.
The long-term follow-up of this low-risk, non-invasive trial called ‘The Beans to Enrich the Gut Microbiome vs. Obesity’s Negative Effects (BE GONE)’ conducted at the MD Anderson Cancer Center in Texas, United States of America (USA) is ongoing.
Study: Modulation of prebiotic food source affects inflammation and immune-regulating gut microbes and metabolites: insights from the BE GONE trial. Image Credit: Michelle Lee Photography/Shutterstock.com
Background
Studies have shown that patients with obesity, unhealthy diets, and a history of colorectal cancer or precancerous polyps often have long-term imbalances, even after successful cancer treatment or polyp removal.
Adjusting the diet to modify the gut microbiome appears to be a promising strategy for the management of high-risk patients. However, ensuring that these people, especially those recovering from cancer, can successfully adopt and tolerate dietary changes is a significant challenge.
In this context, the small navy blue bean stands out. It is a nutrient rich food that is affordable and widely available. Acting as a prebiotic, navy beans may play a key role in restoring diversity to the gut microbiome. This may improve the gut and metabolic health of cancer survivors.
A growing body of evidence suggests that these patients have gut dysbiosis due to metabolic dysregulation in the production of branched-chain amino acids, increased gut permeability, and low-grade endotoxemia.
About the study
In this study, the researchers first subjected all the rollers to a four-week equilibration/run-in period, after which they were randomly divided into two groups.
The first group (control) consisted of participants on a normal diet without dry beans (control), while the other group (test) started an eight-week intervention diet.
The intervention diet involved gradually adding navy beans to the participants’ normal diet (1 cup per day) for eight weeks and supplemented with 16 g dietary fiber, 14 g protein, and 220 kcal.
This was followed by an immediate transition to the control diet, which facilitated cross-over comparisons of changes in stool and blood markers every four weeks during the eight-week intervention to measure compliance during the intervention period.
The main outcome was intra- and inter-individual mediated changes in the gut microbiome. Specifically, they assessed gut microbial alpha diversity, relative abundance of individual taxa, and beta diversity distances from ribosomal ribosomal acid (rRNA) gene profiles for each subject at each time point.
The researchers also assessed the stability of these measures during the “return to control” and “remain control” periods.
In addition, the researchers performed a simultaneous global metabolomic analysis to identify changes in circulating metabolites (proteomic biomarkers) associated with the intervention and changes in microbial composition.
Results
The study began with an initial contact with 240 people, 71 of whom gave their consent to participate. Ultimately, 69 people participated in the 16-week trial, with an 87% completion rate. Of these, 48 participants were included in the intention-to-treat (ITT) analysis.
The study noted that the eight-week intervention resulted in a small increase in fiber consumption for most of the participants, who initially had a dietary fiber intake below the recommended threshold.
Although some participants reported mild to moderate bloating and changes in bowel habits, adherence to the dietary intervention prescribed in the study was high.
In particular, those who experienced changes in their bowel habits also saw an increase in the diversity of their gut microbes during the intervention period.
A linear mixed model analyzing temporal changes in microbial taxa showed that some bacterial taxa decreased post-diet intervention while others increased, with more significant changes in alpha and beta diversity in older participants.
Interestingly, some bacteria that were transferred were sulfur metabolizing species (e.g., Bilophila wadsworthia) have established links with colorectal cancer.
Shotgun metagenomic sequencing of 140 samples from 48 participants confirmed the consistency of these findings.
Moreover, it showed how the prebiotic dry bean intervention reduced the pathways of microbial gene content related to branched chain amino acid biosynthesis and fermentation. Metagenomic sequencing also revealed increases in Eubacterium rectale and Bifidobacterium adolescentis species.
The study intervention increased inverse Simpson index scores, an indicator of alpha microbial diversity, which indicates a more even distribution of all types of bacteria.
The relative abundance of Rosebury and Streptococcus decrease and that’s it Facalibacterium surge
Regarding effects on host metabolism, picobic acid (PA) and S-(5′-Adenosyl)-l-methionine (SAM) increased during the intervention, while indole derivative decreased.
Similarly, trigonelline and theophylline increased during the intervention but did not change when participants switched to the control. Additionally, the Bean “dose” was sufficient to improve LDL and overall metabolic health.
In addition, the dry bean intervention resulted in an increase in fibroblast growth factor (FGF-19), a decrease in levels of interleukin ten alpha receptor (IL10ra), and several other immuno-oncology cytokines, e.g. programmed cell death 1 ligand 1. (PD-L1). All of these microbial metabolites and biomarkers have potential therapeutic relevance.
Conclusions
This trial showed that adding one cup of prebiotic navy beans to the regular diet is a safe and scalable strategy to modify the gut microbiome of colorectal cancer patients, who could not comfortably sustain other dramatic changes without support.
In fact, prebiotic foods show the potential to be a significant component of a combined dietary regimen for patients with inflammatory bowel disease and diabetes as well.
Future research should advance understanding of the metabolites and biological markers that could complement this nutritional strategy and improve clinically relevant outcomes achieved with prebiotic foods.
