Thanks to the Human Microbiome Project, we know that the human body contains about two to six pounds of microorganisms and that according to some estimates these microorganisms out-number our own cells by as much as ten to one. Other estimates put the number lower, but the fact remains that we are home to trillions of microbes, the largest number of which are found in our gut. And while the mapping of the microbiome is complex and not yet finished, we know that diversity is everything. As in agriculture, diversity tends toward a state of health and balance; monoculture tends toward one of sickness and disease.
Starting in our nose and sinus passageways, and extending all the way to the anus, our gastrointestinal (GI) tract is filled with an incredible diversity of bacteria, viruses, fungi, and sometimes larger organisms. The GI tract can be thought of as a long, hollow tube, divided into different sections, each with a different function. The entire tract is covered with a layer of microorganisms, as well as a layer of hairlike protrusions called villi. Microvilli are similar and have some of the same functions, but can also be found in some other parts of the body, such as white blood cells.
Like our gut flora, intestinal villi (and microvilli) are critical to our health. On the one hand, they enable good absorption of nutrients from the food we eat. Increasing the surface area of the intestinal wall, the villi absorb nutrients and deposit them in the capillaries that lie just below, eventually delivering them into circulation for use as the building blocks of our cells and tissues. The intestinal villi also create tight junctions that result in the selective permeability of the gut wall, preventing proteins, toxins, and other molecules from gaining access to the bloodstream.
Like a well-constructed brick wall, the bricks (read: plump, healthy cells) fit perfectly next to one another. Underneath the villi is a layer of collagen and then a muscular wall, which provides structure and stability to the GI tract. The muscular wall is responsible for the contractile movement resulting in peristalsis and the ability to defecate. Without it, the remnants of our food would not move down and out, and our digestive system would grind to a halt.
I often tell my patients to imagine their GI system like a healthy meadow. Healthy subsoil will provide the structure and foundation upon which the upper layers rest. This subsoil is the muscular layer of our GI tract. Then there is the topsoil (the villi), the meadow’s nutritive layer; when healthy, this layer provides the nutrients and habitat for the microbial community.
In a pasture or garden, a healthy topsoil gives rise to a thick and vibrant grassy layer filled with an incredible diversity of plant life, everything from perennial grasses, wildflowers, and annual grasses to bushes and trees.
The Root of Autoimmune Disease
Can Be Found in the Gut
The following excerpt is from Dr. Cowan’s book
(Chelsea Green Publishing, September 2018) and is reprinted with permission from the publisher.