The human gut microbiota, particularly the Lachnospiraceae family, plays a crucial role in health and disease. Lachnospiraceae are core gut bacteria that colonize the intestinal lumen from birth and increase in abundance with age. They are key producers of short-chain fatty acids (SCFAs), which influence host physiology. However, different Lachnospiraceae taxa are associated with various diseases, and their impact on host health is inconsistent across studies. This review discusses the physiological and pathological roles of Lachnospiraceae, focusing on their ability to promote human health through diet and their metabolites. The review also explores how nutrients from the host diet influence Lachnospiraceae growth and how their metabolites affect host physiology. Lachnospiraceae are anaerobic, fermentative bacteria that degrade complex carbohydrates, producing SCFAs like butyrate, propionate, and acetate. These SCFAs have beneficial effects on gut health, including improved epithelial integrity, immune function, and metabolic regulation. However, some Lachnospiraceae species also produce harmful metabolites, such as indoxyl sulfate and p-cresyl sulfate, which are associated with metabolic diseases, liver disease, and kidney disease. The review highlights the role of Lachnospiraceae in various diseases, including metabolic syndrome, obesity, diabetes, inflammatory bowel disease (IBD), and chronic kidney disease (CKD). It also discusses the impact of diet on Lachnospiraceae diversity, showing that certain dietary components, such as fiber and plant-based nutrients, promote the growth of beneficial Lachnospiraceae species. The review concludes that Lachnospiraceae play a significant role in human health and disease, and further research is needed to understand their interactions with the host and the potential for targeted therapies to improve gut health and prevent diseases.The human gut microbiota, particularly the Lachnospiraceae family, plays a crucial role in health and disease. Lachnospiraceae are core gut bacteria that colonize the intestinal lumen from birth and increase in abundance with age. They are key producers of short-chain fatty acids (SCFAs), which influence host physiology. However, different Lachnospiraceae taxa are associated with various diseases, and their impact on host health is inconsistent across studies. This review discusses the physiological and pathological roles of Lachnospiraceae, focusing on their ability to promote human health through diet and their metabolites. The review also explores how nutrients from the host diet influence Lachnospiraceae growth and how their metabolites affect host physiology. Lachnospiraceae are anaerobic, fermentative bacteria that degrade complex carbohydrates, producing SCFAs like butyrate, propionate, and acetate. These SCFAs have beneficial effects on gut health, including improved epithelial integrity, immune function, and metabolic regulation. However, some Lachnospiraceae species also produce harmful metabolites, such as indoxyl sulfate and p-cresyl sulfate, which are associated with metabolic diseases, liver disease, and kidney disease. The review highlights the role of Lachnospiraceae in various diseases, including metabolic syndrome, obesity, diabetes, inflammatory bowel disease (IBD), and chronic kidney disease (CKD). It also discusses the impact of diet on Lachnospiraceae diversity, showing that certain dietary components, such as fiber and plant-based nutrients, promote the growth of beneficial Lachnospiraceae species. The review concludes that Lachnospiraceae play a significant role in human health and disease, and further research is needed to understand their interactions with the host and the potential for targeted therapies to improve gut health and prevent diseases.