Emerging Evidence on the Effects of Dietary Factors on the Gut Microbiome in Colorectal Cancer

Abstract

Dietary factors have important role in modulating the gut microbiome, which in-turn regulates the molecular events in colonic mucosa. The composition and resulting metabolism of the gut microbiome are decisive factors in colorectal cancer (CRC) tumorigenesis. Altered gut microbiome is associated with impaired immune response, and the release of carcinogenic or genotoxic substances which are the major microbiome-induced mechanisms implicated in CRC pathogenesis. Diets low in dietary fibers and phytomolecules as well as high in red meat are important dietary changes which predispose to CRC. Dietary fibers which reach the colon in an undigested form are further metabolized by the gut microbiome into enterocyte friendly metabolites such as short chain fatty acid (SCFA) which provide anti-inflammatory and anti-proliferative effects. Healthy microbiome supported by dietary fibers and phytomolecules could decrease cell proliferation by regulating the epigenetic events which activate proto-oncogenes and oncogenic pathways. Emerging evidence show that predominance of microbes such as Fusobacterium nucleatum can predispose the colonic mucosa to malignant transformation. Dietary and lifestyle modifications have been demonstrated to restrict the growth of potentially harmful opportunistic organisms. Synbiotics can protect the intestinal mucosa by improving immune response and decreasing the production of toxic metabolites, oxidative stress and cell proliferation. In this narrative review, we aim to update the emerging evidence on how diet could modulate the gut microbial composition and revive colonic epithelium. This review highlights the importance of healthy plant-based diet and related supplements in CRC prevention by improving the gut microbiome.

Gut microbiota, inflammatory bowel disease and colorectal cancer

“…ETBF is the most frequent anaerobe isolated from cases of diarrhea, peritonitis, intra-abdominal abscesses, and sepsis, and there is a positive correlation between the presence of ETBF and active IBD and CRC[ 38 ]. According to Appunni et al [ 39 ], co-colonization of toxigenic E. coli and ETBF in mice resulted in increased production of pro-inflammatory IL-17 and subsequent DNA damage, which could accelerate the development of CRC[ 39 ]. In addition, the toxin in ETBF could induce c-myc expression and IL-8 secretion causing oxidative DNA and epithelial barrier damage, and STAT3/Th17 immune responses activation, which are further correlated with an increased risk of CRC[ 38 ].…”

Emergence of nutrigenomics and dietary components as a complementary therapy in cancer prevention

“…Short chain fatty acids (SCFAs), choline metabolites, and lipids, among other microbial bioactive substances, play a crucial role in activating host epigenome not just in the gut, but also in the hepatic, cardiac, and central nervous system (Qin and Wade 2018). An altered gut microbiota is associated to the generation of carcinogenic or genotoxic compounds, which is one of the primary microbiome-induced mechanisms implicated in colorectal cancer development (Appunni et al 2021). The gut microbiota is one of the most affected "organs" by food consumption, and it has emerged as a crucial effector in the diet-cancer association (Song et al 2015).…”

In Vitro Fermentation of Beechwood Lignin–Carbohydrate Complexes Provides Evidence for Utilization by Gut Bacteria

“…Fibers in dietary products are capable of resisting digestion and absorption by the small intestine, allowing them to reach the large intestine undigested. They could be metabolized by certain intestinal microflora in an anaerobic environment to produce substances such as short-chain fatty acids (SCFAs), thereby altering the composition of gut microbes to affect the body’s health [ 6 , 7 , 8 ]. The chemical characteristics of dietary fibers, which include polymerization degree, composition, and chemical bond form, have different effects on gut microbes [ 9 , 10 , 11 ].…”