Nutrition & Health

The human gastrointestinal (GI) tract represents one of the largest interfaces (2500–4300 sq ft!!) between the host, environmental factors and antigens in the human body. In an average life time, around 60 tons of food pass through the human GI tract, along with an abundance of microorganisms from the environment which impose a huge threat on gut integrity. The collection of bacteria, colonizing the GI tract is termed the ‘gut microbiota’ and has co-evolved with the host (us humans) over thousands of years to form an intricate and mutually beneficial relationship. The number of microorganisms inhabiting the GI tract has been estimated to exceed 10¹⁴ (one hundred trillion!!), which encompasses ∼10 times more bacterial cells than the number of human cells and over 100 times the amount of genomic content of the human genome. As a result of the vast number of bacterial cells in the body, the host and the microorganisms inhabiting it are often referred to as a ‘superorganism’.

This 'superorganism' of the human gastrointestinal (GI) tract harbors a complex and dynamic population of microorganisms, the gut microbiota, which exert a marked influence on the host during homeostasis (health) and disease. Multiple factors contribute to the establishment of the human gut microbiota during infancy, better to come through the birth canal than C-Section. Diet is considered as one of the main drivers in shaping the gut microbiota across the life time. Intestinal bacteria play a crucial role in maintaining immune and metabolic homeostasis and protecting against pathogens. Altered gut bacterial composition (dysbiosis) has been associated with the incidence many inflammatory diseases like diabetes, arthritis, and asthma and infections. The human gut microbiota are very complex and have inter-individual variations, heterogeneity of bacterial communities along and across the GI tract, functional redundancy and there is a need to distinguish cause from effect in states of dysbiosis. 

Based on Introduction to the Human Gut Microbiota by E Thursby and N Juge in Biochemical Journal , 16 May 2016 doi: 10.1042/BCJ20160510