Gut microbiomes are dynamic communities varying from population to population and throughout life. In Western societies, a toxic metabolic shift of gut microbiomes is a driver and underestimated risk factor for the development of many noncommunicable chronic pathologies. This book identifies the root cause of these deleterious microbial changes. During the last several decades, increased consumption of animal products, coinciding and correlating with global climate change, has been a contributing cause of undesirable gut microbiome changes.