Diet and dietary components have profound effects on the composition of the gut microbiota and are among the most important contributors to the alteration in bacterial flora. This review examines the effects the “Western”, “plant-based”, “high-fat”, “medical ketogenic”, and “Mediterranean” diets have on the composition of the gut microbiota in both mice and human subjects. We show that specific dietary components that are commonly found in the “plant-based” and “Mediterranean” diet play a role in shifting the microbial composition. This review further evaluates the bacterial metabolites that are associated with diet, and their role in systemic inflammation and metabolic endotoxemia. Furthermore, the associations between diet/dietary components and altering bacterial composition, may lead to potential therapeutic targets for type II diabetes, obesity, and inflammatory diseases.

Colorectal cancer is the third most common cancer worldwide. Etiology of colon cancer continues to be investigated with research fndings ranging from environment to diet to inherited gene mutations. Risk factors associated with colon cancer include familial history of colon cancer and inflammatory bowel disease, as well as lifestyle-related modifiable influences like diet, weight, and exercise. Recent findings point to the connection between diet and gut microbiota, which is highly affected by changes in diet promoting either an environment of beneficial bacteria or dysbiosis. Dietary effects on the microbiome can impact health outcomes, including an increased risk for colorectal cancer. Although the mechanisms behind the effect of gut microbiota on the development of colorectal cancer continues to evolve, its effect on both inflammation and immune response may play a key role. Further, after development of colorectal cancer diagnosis, the changes to gut microbiota have a potential to continue to influence the effectiveness of therapy and treatment. This review presents the current knowledge around the diet-modulated gut microbiome and its association with, risk for, development of, and treatment of colorectal cancer. Overall, further research on dietary elements that affect the gut microbiome and its subsequent effect on development and treatment of colorectal cancer is needed for applicable recommendations that can be made for dietary modulation of the gut microbiota for improved health outcomes.