The human body is home to trillions of microorganisms that play an important role in digestion, immunity, and overall health. This collection of microorganisms is called the human microbiome. Understanding the microbiome helps doctors evaluate digestive health and identify possible imbalances that may contribute to disease.
Human Microbiome
The human microbiome refers to the vast community of microorganisms living on and inside the body. These microbes include bacteria, viruses, fungi, and other microscopic organisms.
Researchers estimate that the human body contains around 100 trillion microbes, and together they may weigh up to 2 kilograms (4–5 pounds). While they are microscopic, they play an essential role in maintaining normal body functions such as digestion, immune defence, and nutrient absorption.
Gut Microbiome
Most of these microorganisms live in the digestive system. In fact, more than 95% of the human microbiome resides in the gastrointestinal (GI) tract, with the highest concentration found in the large intestine.
The gut microbiome is made up of four major groups of microorganisms:
Among these groups, bacteria make up more than 95% of the gut microbiome. Scientists have identified over 10,000 microbial species, and each individual may carry between 1,000 and 2,500 different species of microbes in their digestive system.
Microbiome and Diseases
Most gut microbes are harmless or even beneficial. They help break down food, produce vitamins, and support the immune system. However, when the balance of microorganisms changes, it may lead to digestive issues and other health concerns.
Only a small percentage of gut microbes (less than 5%) are harmful, but imbalances in the microbiome have been linked to many chronic health conditions. One of the most common causes of digestive problems is reduced microbial diversity, which can lead to intestinal dysbiosis—a disruption in the natural balance of microorganisms in the gut.