The topic covered in this article was not even discussed when I first went to college—decades ago—and little was known about it. The study of what is now known as the human microbiome can be traced as far back as the work of Antonie van Leeuwenhoek (1623-1723). Intense interest resurged in 2007 with the Human Microbiome Project. Most of the research has occurred in the last 17 years, but has become more popular in the last 10 years.
So what is the human microbiome?
The complex scientific definition – Human microbiome, the full array of microorganisms (the microbiota) that live on and in humans and, more specifically, the collection of microbial genomes that contribute to the broader genetic portrait, or metagenome, of a human. The genomes that constitute the human microbiome represent a remarkably diverse array of microorganisms that includes bacteria, archaea (primitive single-celled organisms), fungi, and even some protozoans and nonliving viruses.
A less complex definition – the full complement of microbes and their genes and genomes in or on the human body.
The simple definition – a bustling community of microbes within your body that significantly influences your overall wellbeing.
Bacteria are by far the most numerous members of the human microbiome—estimated at between 75 trillion and 200 trillion individual organisms—while the entire human body consists of about 50 trillion to 100 trillion body cells. The sheer microbial abundance suggests that the human body is in fact a “supraorganism,” a collection of human and microbial cells and genes and thus a blend of human and microbial traits.
Did You Know? Over half of the cells in your body are not even human cells. If collected together and weighed, the non-human cells would weigh over four pounds.
These microbial cells, microbiota, are found on the body and in body orifices with the largest number being in the nose and nasal passages, in the mouth, the gastrointestinal tract, urinary tract and the genital areas. The area that contains the largest amount of microbiota is the intestinal area, especially the large intestine. Five hundred to 1,000 different species of bacteria live in the intestine, totaling at least 38 trillion cells. These gut bacteria are also known as the gut flora. It has been said by some that if you are going to focus on one aspect of health, work on gut health.
Scientists are only just beginning to understand what these microbes do, how they function, and how they can be manipulated to benefit human health. Research on the human microbiome has benefited tremendously from other recent advances in microbiology, not the least of which is a growing recognition that the vast microbial diversity exists.
So why is the human microbiome so important? It interacts with almost every body system. In fact, the gut microbiome has been called the “second brain” because it interacts so closely with our brain, brain chemistry, and its many functions.
The microbiome is very active in the metabolism of our food. Chronic and infectious disease risks are also affected by our microbiome. The gut also is intimately connected to our immune system with about 70% to 80% of the immune system being in the gut. We also know that our microbiome has effects on our mood and behavior. Digestion, sleep, and cardiovascular health are also closely linked to the microbiome, emphasizing its importance in maintaining a healthy, living human. The microbiome can potentially prevent or help fight some forms of cancer, and may help prevent or treat some forms of dementia.
Therefore, prioritizing the well-being of our microbiome is a crucial step toward achieving overall health and vitality, and will be the subject of a future article.
Sources: ncbi.nlm.nih.gov/books/NBK154100; britannica.com/science/human-microbiome#Overview