Human Gut Microbiota: Friend or Foe?

Abstract

The human gut is a house to approximately 1,000 different species of bacteria. The bacterial composition of gut microbiota is influenced by several factors, including age, sex, mode of delivery, geographical location, ethnicity, diet, drugs, and administration of prebiotics and/or probiotics. Similarly, human health depends on the composition of gut microbiome, with gut bacteria playing a crucial role in human physiology. For instance, gut microbiota synthesizes vitamins and amino acids, and affects the biotransformation of bile acid. Intestinal microbiota produces short-chain fatty acids (SCFAs) that stimulate intestinal gluconeogenesis, protect the host from diet-induced obesity, and may play a role as an energy substrate. Changes in the composition of gut microbiota, termed dysbiosis, due to, for example, change in the diet or uptake of certain drugs, may result in metabolic diseases, autoimmune and allergic diseases, cancers, and many others. Conversely, dysbiosis can be a consequence of a disease in several cases. This review outlines the current knowledge of the associations between human gut microbiota and human health and diseases.