Over the last decade there has been an exponential growth in the amount of individuals that are being diagnosed with diseases, such as Irritable Bowel Syndrome (IBS), Crohn's Disease, and food allergies, which are a result of the consequences from the amount and type of microbiota contained within the gastrointestinal tract.  There are also some diseases; Multiple Sclerosis (MS), Chronic Obstructive Pulmonary Disorder (COPD), many autoimmune disorders, and rheumatoid arthritis, that are not apparent as having its causal root stem from the GI tract.  All of these maladies may have a contribution by the bacteria, viruses, and eukaryotes that live inside our intestines.

Scientists are just at the brink of understanding the immense diversity of the microbiome in and on the human body.  There is an estimated 100 trillion microbial cells throughout and on the surface of the human body.  While scientists are elaborating on and discovering elements of the known and unknown microorganisms, within the digestive tract, there is always new information that leads to different questions and protocol for examining the interworking of the human microbiome.  These multitudes of microorganisms each have facets that can work in accordance with or suppress other bacteria, viruses, et cetera.  Within the intestinal system the microbes all play a significant role in the health of the host.  

This article pinpoints a few diseases caused by an imbalance in the GI tract and expounds on how the microbiota are affected.  It also makes mention that one of the known causes of these imbalances is due to the Western style of living that of a high in fat and sugar diet as well as the overuse of antibiotics.  Though the explanation of different underlying causes does not solely implicate that of the modern Western society, there are a number of reasons of the environment and its role in the changes of the internal and external microbial population throughout the life span of a human.