The human gut microbiota, a diverse microbial community, plays a crucial role in shaping the biochemical profile of the diet and influencing host health and disease. This review discusses the main gut microorganisms, particularly bacteria, and their metabolic pathways associated with the metabolism of dietary carbohydrates, proteins, plant polyphenols, bile acids, and vitamins. The review also focuses on methodologies for exploring gut microbial pathways of metabolism, including mathematical models, omics techniques, isolated microbes, and enzyme assays. Key findings include the production of short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate, which have beneficial effects on human health, and the role of bacterial cross-feeding in SCFA production. The review highlights the importance of understanding the gut microbiota's impact on human metabolism and health, and the need for further research to identify specific microorganisms involved in different metabolic processes.The human gut microbiota, a diverse microbial community, plays a crucial role in shaping the biochemical profile of the diet and influencing host health and disease. This review discusses the main gut microorganisms, particularly bacteria, and their metabolic pathways associated with the metabolism of dietary carbohydrates, proteins, plant polyphenols, bile acids, and vitamins. The review also focuses on methodologies for exploring gut microbial pathways of metabolism, including mathematical models, omics techniques, isolated microbes, and enzyme assays. Key findings include the production of short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate, which have beneficial effects on human health, and the role of bacterial cross-feeding in SCFA production. The review highlights the importance of understanding the gut microbiota's impact on human metabolism and health, and the need for further research to identify specific microorganisms involved in different metabolic processes.