Human gut microbiota, nutrition and health

Human gut microbiota is the complex community of microorganisms that live in the digestive tracts, including bacteria, archaea, virus, fungi and protists. These microorganisms coevolved together with human body for a long history, forming a balanced micro-ecosystem. Recent researches discovered the close association between gut microbiota and human health. The gut microbiota was thought to be the biggest endocrine "organ", which keeps and restores human health by regulating the its composition and structure. Dysregulation in the composition and diversity of microbiota (dysbiosis) is closely associated with diverse metabolism and immune disorders, such as diabetes, allergy, autoimmunity, and gastrointestinal inflammatory disorders. Thus, a balanced network between gut microbiota and human body will be of great help for diagnosis, treatment and prognosis in the field of precision medicine. Gut microbiota also interacts with diet to degrade nutrients and provide additional nutrients. Meanwhile, faecal bacteria can exert a fundamental role in modulating energy metabolism. Studies have shown that in obesity individuals, the gut microbiota composition can be significantly different from that of lean individuals, and that modifications of gut microbiota composition can be associated with increases or reductions of body weight and body mass index. On the other hand, gut bacterial was related with nutrients absorption. Such as, decreased abundance of Lactobacillus maybe relate with iron (Fe) deficiency, which indicated the intimate connection between gut microbiota and nutrients. Development of nutriology has contributed greatly to human health. A well-balanced diet is the basis for a healthy life. Both the western diet and special diets can have a relevant impact on the microbiome and promote the development of various diseases. An increasing in food-related disorders in recent years, largely associated with dramatic changes in food consumption trends and main nutrients. Nutrition has a very special influence on the microbiome as it is an important factor throughout age. Gut bacteria are specialized in the fermentation of various substrates, thus, complex diets can lead to a number of metabolic products, especially vitamins and SCFAs, which are important to human health. Dietary-associated changes in compositional and functional microbiota traits should be correlated with the health status for the future development of dietary recommendations and potential clinical interventions. We have realized the close relationship between human body, gut microbiota, nutrients and immunity, which will bring an unprecedented opportunity for developing precision nutrition. This review will focus on the gut microbiota, nutrition and health. Due to rapid advances in this inter-discipline, we here only choose several facets to discuss.