Gut microbiota plays a crucial role in preventing cancer by influencing the immune system, regulating inflammation, and producing beneficial metabolites. The microbiota can stimulate the immune system to recognize and destroy cancer cells, and some bacterial strains can directly inhibit the growth of cancer cells. Additionally, gut bacteria can produce short-chain fatty acids (SCFAs), which have anti-inflammatory properties and can prevent DNA damage that otherwise can lead to cancer development. Moreover, certain microbial metabolites, such as indole-3-acetic acid (IAA) and butyrate, can induce apoptosis (programmed cell death) in cancer cells, further inhibiting tumor growth. Overall, gut microbiota can help to maintain good health by promoting a healthy immune system, reducing inflammation, and producing beneficial metabolites. This book is a comprehensive guide to understanding the role of gut microbiota in human health. It presents the latest research on gut microbiota, from the characterization of different microbial species to their functions in food conversion and cancer prevention. It sheds light on the diverse composition of gut microbiota, identified through DNA sequencing technology, and how it is influenced by various factors such as diet, genetics, and lifestyle. It highlights promising research on how gut microbiota can be manipulated to prevent health disorders. It is a must-read for anyone interested in understanding the complex and dynamic relationship between gut microbiota and human health.