Introduction

The adult human gastrointestinal tract (gut) is a tube about a 20-foot from mouth to anus.  The lining of this tube is not a smooth surface but rather made up of tiny but numerous peaks and valleys of intestinal cells. These peaks and valleys are so compact and numerous that if you could open the tube and spread it out flat, its surface area would be roughly 3,000 square feet, or about the size of a doubles tennis court.

                                                                                                      

The Surface Area of a Grown Up Gut

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Within this vast space of land inside all our guts live millions of  bacteria and related microorganisms that help the human body carry out its normal functioning when healthy. The term microbiome is used when describing the group of healthy microscopic beings that reside within or on us. In addition to the gut microbiome, there are also microbiomes in our mouth, respiratory tract tissue, urogenital tract, and on our skin. Of these collections of microscopic creatures, the gut microbiome is the largest in the human body. It is currently estimated that the microscopic organisms composing our total body microbiome outnumber our human cells up by at least 1.3 to 1. By the time we become adults, it is estimated 3 to 4 pounds of our body weight are the bacteria making up our microbiome, which is about the same size as the adult human brain. Even more astounding is that the genetic material carried by the organisms making up the microbiome is thought to be about 5 million genes, versus the humble 20,000 human genes we are each known to carry. 

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The science of understanding the human microbiome has taken off this past decade. The U.S. National Institute of Health launched the Human Microbiome Project in 2008 in order to better understand this complex ecosystem residing within each of us. It has now been demonstrated that a healthy collection of these microorganisms is essential for human physiology, immune system development, digestion, detoxification reactions, metabolism, vitamin synthesis, and releasing vital neurotransmitters, which are the brain hormones that among other critical functions, help us control our moods. An unhealthy microbiome has been linked to such diverse diseases as inflammatory bowel disease, obesity, cancer and autism.

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Healthy Microbiomes Promote Good Guts

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Like a well maintained garden brimming with blossoming flowers, fluttering butterflies, shiny grasses, and chirping birds, the healthy human microbime, composed of friendly bacteria and related microorganisms, is a functional ecosystem with all the parts working together to maintain vitality of the whole. The unhealthy microbiome is more like a putrid, malodorous junkyard made up of unfriendly bacteria, yeast, and viruses.  These organisms do not allow for optimal health of the whole, or human host, and this is how disease can then take hold. 

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Unhealthy Microbiomes Can Cause Leaky Guts

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Also residing within our guts are the cells that make up about 70% of a human's immune system. These specialized cells are responsible for the body’s ability to mount an inflammatory response to a stressor. The immune system within the gastrointestinal tract is highly sophisticated because it has the all important task of having to determine if what has passed from our mouth down the tube is friend or foe. Healthy components of food are recognized by these cells of the immune system as friends and do not normally illicit an inflammatory response. Pathogenic or bad bacteria, viruses or yeast, as well as other toxins such as pesticides and certain food additives are foes and can cause the immune system to mount a response to rid the body of them and prevent tissue damage as much as possible in a healthy person.

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A healthy person has tight connections or junctions between the cells that line the gastrointestinal system or gut. The tightness in the way these cells are linked together prevents foes or toxins  from leaking from the gut into the surrounding bloodstream and invading the rest of the body.

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Certain foods and toxins are known to cause a protein, called zonulin, to be secreted from the gut which dissolves the tight junctions of the barrier cells that line it. This is called increased intestinal permeability or leaky gut. There is data to suggest that certain substances such as gluten, infectious organisms, and toxins such as pesticides can cause the release of zonulin. Certain drugs such as antibiotics and nonsteroidal anti-inflammatory drugs like Ibuprofen have also been linked to leaky gut.

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Increased physical and psychological stress, specifically because of the release of stress hormones has recently been implicated as an additional cause of increased intestinal permeability.

 

Leaky Guts Result in Chronic Inflammation

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When the barrier cells of the gut are no longer tightly knitted to each other, toxins, microbes and undigested or partially digested pieces of food can leak from the gut into blood stream. As this happens, the immune system sees this foreign material in the blood and mounts an inflammatory response to it. This inflammation that occurs in the gut changes the landscape from healthy garden to ailing junkyard. Once the permeability of the intestine lining is compromised, the body will continue to get exposed to ongoing molecules passing into bloodstream and trigger an ongoing immune system response.

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This immune system response includes the production of antibodies, which can circulate anywhere in the body, and trigger the development of chronic or pathological inflammation anywhere in the body. It has been proposed that the combination of leaky gut, genetic predisposition and environmental trigger are required for the development of autoimmunity.

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Tend the Garden

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Because our gut microbiome appears to be essential in assisting us with absorption and digestion of food, vitamin synthesis, making our important brain hormones and allowing our immune systems to function properly, it is vital that this collection of microorganisms inside our gut is as healthy as possible.

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If you suspect your, or a loved one’s microbiome may not be thriving, the good news is that there are things that can be done to improve its state. Much like transforming a junkyard to a thriving garden involves removal of trash and weeds, repairing and replacing the ground with healthy soil and fertilizers, repairing and re-inoculating the site with healthy critters and plants; the transformation of the human gut microbiome may be equally adaptable to change. And with change, can come thriving health.