by A new study in eBioMedicine investigated the impact of incorporating canned white beans into the regular diet for eight weeks.
This research focused on how such a change in diet affects the gut microbiota, as well as circulating markers and metabolites, in obese people with a history of colorectal neoplasia and precancerous polyps. The study also included participants taking medications such as statins or metformin.
Long-term follow-up of this non-invasive, low-risk trial called ‘Beans to Enrich the Gut Microbiome Against the Negative Effects of Obesity (BE GONE)’ was carried out at the MD Anderson Cancer Center in Texas, United States. United (USA) is underway.
Study: Modulating a prebiotic food source influences inflammation and gut microbes and metabolites that regulate the immune system: 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 experience long-term imbalances in their gut microbiome, even after successful cancer treatment or polyp removal.
Adjusting the diet to modify the gut microbiome appears to be a promising strategy for the treatment of high-risk patients. However, a major challenge is ensuring that these people, particularly those recovering from cancer, can successfully adopt and tolerate dietary changes.
In this context, the small white navy blue bean stands out. It is a nutrient-rich, affordable and widely available food. By acting as a prebiotic, white beans may play a key role in restoring gut microbiome diversity. This could potentially improve the gut and metabolic health of cancer survivors.
A growing body of evidence suggests that these patients have intestinal dysbiosis due to metabolic dysregulation in branched-chain amino acid production, increased intestinal permeability, and low-grade endotoxemia.
About the study
In the present study, the researchers first subjected all enrollees to a four-week equilibration/preparation period, followed by a random division into two groups.
The first group (control) consisted of participants who followed a regular diet without dried beans (control), and the other group (test) began an eight-week intervention diet.
The intervention diet involved gradually adding navy beans to participants’ regular diet (1 cup/day) over eight weeks and supplementing them with 16 g of dietary fiber, 14 g of protein, and 220 kcal.
It was followed by an immediate crossover to the control diet, which facilitated cross-comparisons of changes in stool and blood markers every four weeks during the eight-week intervention to measure compliance during the intervention period.
The primary outcome was intra- and inter-individual changes during the intervention in the gut microbiome. Specifically, they assessed gut microbial alpha diversity, relative abundance of individual taxa, and beta diversity distances from 16S ribosomal ribonucleic 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 “stay in control” periods.
Additionally, the researchers performed a parallel 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 initial contact with 240 people, of whom 71 gave their consent to participate. In the end, 69 people participated in the 16-week trial, for a completion rate of 87%. Of these, 48 participants were included in the intention-to-treat (ITT) analysis.
The study noted that the eight-week intervention led to a slight increase in fiber intake for most participants, who initially had dietary fiber intake below the recommended threshold.
Although some participants reported experiencing mild to moderate bloating and changes in bowel habits, overall compliance with the dietary intervention prescribed in the study was high.
Notably, those who experienced changes in their bowel habits also saw an increase in the diversity of their gut microbiome during the intervention period.
A linear mixed model analyzing temporal changes in microbial taxa showed that some bacterial taxa decreased post-diet intervention and others increased, with more significant changes in alpha and beta diversity in older participants.
Interestingly, some bacteria that moved during the intervention were sulfur-metabolizing species (e.g. Bilophila wadsworthia) that have established links to colorectal cancer.
Metagenomic sequencing of 140 samples from 48 participants confirmed the consistency of these results.
Furthermore, it showed how prebiotic intervention with dried beans downregulated microbial gene content pathways associated with branched-chain amino acid biosynthesis and fermentation. Metagenomic sequencing also revealed increases in rectal eubacteria and Adolescent Bifidobacterium species.
The study intervention increased Reverse Simpson Index scores, an indicator of microbial alpha diversity, indicating a more balanced distribution of all types of bacteria.
The relative abundance of rosaburia and Streptococcus decreased while that of Faecalibacterium arose.
Regarding effects on the host metabolome, pipecolic acid (PA) and S-(5′-adenosyl)-l-methionine (SAM) increased during the intervention, while an indole derivative decreased.
Likewise, trigonelline and theophylline increased during the intervention but did not change when participants switched to control. Additionally, the “dose” of beans was enough to improve LDL and overall metabolic health.
Furthermore, the dry bean intervention caused an increase in fibroblast growth factor (FGF-19), a decrease in the levels of interleukin ten receptor alpha (IL10ra) and several other immuno-oncological cytokines, e.g. programmed cell death. (PD-L1). All of these metabolites and microbial biomarkers have potential therapeutic relevance.
Conclusions
This trial demonstrated that adding one cup of prebiotic white beans to the regular diet was a safe and scalable strategy to modulate the gut microbiome of colorectal cancer patients, who may not be able to comfortably endure other dramatic changes without support.
Indeed, prebiotic foods show the potential to become a prominent component of complementary dietary regimens for patients with inflammatory bowel disease as well as diabetes.
Future research should advance the understanding of metabolites and biological markers that could complement this dietary strategy and improve clinically relevant outcomes obtained with prebiotic foods.
