The adult human gut contains 100 trillion microorganisms, including bacteria, viruses, fungi, and protozoa. The microbiota makes up to 10 times more microbial cells than the human body, and collectively, the genome contains 100 times as many genes as our own cells. So, we are not individuals but an ecosystem constantly interacting with the microbial world within us. 

When there is an alteration of the composition and reduced diversity, it is called Dysbiosis, which is associated with many disorders such as colon cancer, SIBO, IBS, IBD, anxiety, liver disease, multiple sclerosis, fatty liver disease, depression, anxiety, Parkinson’s disease, dementia, obesity, cardiovascular disease, just to name a few. The good news is that dysbiosis is largely preventable through dietary and lifestyle changes.

While the gut is sterile in the mother’s womb, it begins to harbor the microbiome during and after birth. By the first year of life, 70% of the microbiome is established, and it becomes adult-like within three years. After birth, diet is the driving factor in shaping the gut microbiome in composition and function. 

A fascinating study, referenced below, is the first large cohort study of the effects of migration from Southeast Asia to the United States on the human microbiome. Within months of moving from Southeast Asia, significant changes in the biome occurred, leading to a loss of organisms and functional diversity. These immigrants had a near complete loss of enzymes, such as glycoside hydrolases, that break down specific fibers. This study sheds light on the profound impact of environmental changes on our microbiome.