The wall, or lining of the gastrointestinal (GI) tract is the largest surface of the human body that is exposed to the external environment. Previously, it was thought that the surface of the GI tract was as big as a tennis court, but now scientists are countering that understanding, stating that it’s more like half a badminton court.[1]
However, when it comes to the intestinal border, its size may not be as important as its structure and security. A healthy gut is characterized by what is called selective permeability. This means that only certain molecules are allowed to pass the intestinal barrier, and not all. We even see discrimination as to how much of certain molecules such as nutrients, water, and bacterial products are allowed through. Though it seems a majority of molecules—like vitamins, carbohydrates, and fats—are entering the body from the intestines, there are also molecules being secreted into the GI tract from within, like bile. In other words, the border crossing is bi-directional. The interaction of several factors influences what and how much gets through the border.
Let’s explore what constitutes the intestinal barrier. We may think of the intestine as a tube or hose made of a sheath of tissue. In reality, the lining is composed of millions of cells held together by tight junctions. But this cellular wall does not work alone in its task. In fact, there are multiple critically stationed players that function as a part of the border patrol. They include a very important layer of mucous that lines the cell wall. The gut microbiome, which is a vast community of microbes, are another layer of defense. These microbes produce byproducts, some of which nourish and maintain a healthy cellular wall, and others that take out unwanted invaders. The nervous system contributes by keeping things moving through the GI tract.
There are biochemical barriers, as well, comprised of hydrochloric acid and hormones that GI cells produce. There’s even an electrical barrier that repels bacteria from getting too close to the intestinal lining. And, just in case anything gets past these guys, immune cells are strategically posted throughout to protect against enemy invasion. All of these work alongside the intestinal wall structure composed of individual cells that are connected by sealants that we could liken to a mortar of sorts, forming tight junctions.[2]
All these players contribute to healthy barrier function, but have a lot of other very important roles they perform, as well. There is a lot going on in the gut. It is a hub of communication, coordination, and crosstalk between bacteria and immune cells. It is where the Navy Seals of our immune system get trained, and so on. It is all so well organized, until it isn’t. When gut permeability is disrupted it can lead to, or aggravate, a scenario that supports poor health, obesity, inflammation, and disease.
We would do well to take a deep breath right here. That is a lot of information that you may wish we could skip. However, to understand what a leaky gut is, we need to know what a healthy barrier looks like in the first place, how God set it up to work best.
Scripture points us to the value of protective walls by likening them to salvation. “In that day this song will be sung in the land of Judah: We have a strong city; God will appoint salvation for walls and bulwarks.” Isaiah 26:1. Salvation, like a healthy intestinal barrier, provides protection, security, and will make you strong.
[1] https://www.sciencedaily.com/releases/2014/04/140423111505.htm
