Impact of Dietary Intervention on Inflammation and Microbiome Composition Post-Colonoscopy

An altered intestinal gut microbiota, i.e. dysbiosis, has been associated with the development of intestinal diseases including inflammatory bowel disease, colorectal cancer (CRC), and metabolic diseases such as obesity, type 2 diabetes mellitus (T2DM), and cardiovascular disease. Metagenomic analyses have revealed microbial biomarkers and ecological signatures in the fecal microbiome of CRC patients, correlating with chronic inflammation and gut dysbiosis. These factors have demonstrated prognostic relevance for CRC akin to other precursors, including conventional adenoma and serrated polyps.

Bowel lavage, a standard practice for facilitating colonoscopies, may affect the interaction between gut microbes and intestinal phenotypes. Standard bowel preparations have immediate impacts on gut microbiota composition, with alterations typically lasting around 14 days before a partial return to baseline. These changes in gut microbial diversity likely contribute to minor colonoscopy complications such as abdominal discomfort, bloating, diarrhea, and constipation during the recovery period.

Post-bowel lavage dietary intervention could potentially minimize lavage-associated side effects by promoting microbial diversity restoration and systemic inflammation reduction. In a previous mouse study, the investigators discovered that the Standard American Diet (SAD) led to the proliferation of opportunistic pathogens following surgical lavage. This change in microbial composition was linked to increased systemic inflammation and a higher incidence of surgical complications. Additionally, they observed that a high-fiber, low-saturated-fat diet-like a whole food, plant-based (WFPB), Med/DASH diet, and modified Mediterranean diet-can reverse this inflammatory phenotype.

However, there is a lack of interventional trials investigating the health benefits of specific dietary interventions following bowel lavage. Therefore, the investigators propose a human intervention study to assess if daily consumption of a high-fiber diet after colonoscopy will alter the intestinal microbiota, decrease inflammation, and improve digestive health.

This will be a controlled intervention study involving 30 subjects who will be enrolled on a rolling basis as they are identified during the recruitment period. The study begins with an initial visit at Week 1, where blood is collected for immune profiling and metabolomics, and participants start weekly stool collection using the S-Wipe method. At Week 2, a GutLab device is installed in participants' homes for daily stool collection. The colonoscopy occurs at Week 4, followed by a 2-week high-fiber diet provided by Thistle. Throughout the study, blood draws (6 mL) are performed at Weeks 1, 4, 6, and 8, while stool samples are collected weekly via S-Wipe and daily via GutLab. Participants log their food intake with a dietitian three times per week during Weeks 3, 5, and 7, and body composition measurements are taken before the colonoscopy and at the final visit. The study aims to quantify how dietary intervention affects post-lavage microbiome, metabolome, and immune response through analysis of blood and stool samples. Optional follow-ups at 1, 3, and 5 years will assess polyp recurrence. This design enables a comprehensive assessment of a high-fiber diet's impact on intestinal microbiota, inflammation, and digestive health in individuals with a history of polyps undergoing colonoscopy.