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Gut health: How important is the food you eat?

May 12, 2022
Karen Thomas, MSc, BS, RDH, explains how food affects overall health, particularly the health of the gastrointestinal tract. Here, she focuses on leaky gut—what you can do to prevent it and reverse it.

Have you ever wondered if your diet might be endangering your health? The correct answer is yes, it could be. As Hippocrates said, “All disease begins in the gut.”

Today, gut health is a major topic of research and discussion. Have you heard of leaky gut? What is it, and why should we care?

What is the gastrointestinal tract?

The gastrointestinal (GI) tract, or gut, is a long tube that starts with the mouth and ends at the anal passage. As part of the digestive system, the GI tract performs like skin—only on the inside. This tube is supposed to protect the internal parts of our body from the various foods, liquids, medications, bacteria, yeast, and toxins we ingest from the outside world.

Think about it: if you cut your skin and bleed, the bleeding gets your attention, as it should. The gut gives us similar signals, but we often dismiss these indicators.

Additional reading:

What is leaky gut or intestinal permeability?

Leaky gut is caused by openings between the epithelial cells of the lumen, the interior of the gastrointestinal tract. These openings allow food, medications, toxins, bacteria, and yeast to leach into the bloodstream, causing an inflammatory response and then an immune response.1 This is when the body begins giving us clues that something is wrong. These symptoms tell you to wake up! Your body is talking to you.

Here’s how I describe leaky gut: imagine you are holding a cup of coffee, and the cup has small holes in it. As you begin pouring coffee into the cup, the holes allow the coffee to leak out all over. That’s what’s happening in your GI system. The contents of your GI tract—the food particles, medications, bacteria, etc.—leak through the gaps into places they are not supposed to be, like invaders into your blood system.1

Once these intruders enter the blood, the body realizes there are foreign invaders, thus activating the initial immune response and giving us symptoms. Symptoms can include headaches, joint pain, food sensitivities, allergies, skin eruptions, irritable bowels, gas, and brain fog, just for starters.1 If you ignore these signs, your body will trigger a more intense immune response. Listen! Your body is shouting to you.

What are the symptoms of leaky gut?

There are many indications of leaky gut. I tell my students that these signs and symptoms are the body’s love language—a nonverbal signal that something is wrong. It starts like a whisper, almost inaudible. Dismissing these symptoms, we think, “Oh, I’m just getting older,” “It was just something I ate,” or “I’ve had this problem since I was little. It’s normal for me.” But these symptoms are not normal; they’re a signal. So, listen!

Symptoms of leaky gut are diarrhea, constipation, irritable bowel syndrome, asthma, Hashimoto’s thyroiditis, celiac disease, lupus, polycystic ovary syndrome, arthritis, weight gain, brain fog, depression, anxiety, chronic fatigue, fibromyalgia, bloating, pain, allergies, insomnia, sugar cravings, skin problems, acne, and autoimmune conditions, to name a few. All are signs you might have a leaky gut (i.e., intestinal permeability).

What causes leaky gut?

Increased stress and diets high in fats and sugars, such as the standard American diet, can alter your genetic composition. This induces changes in the gut-associated microbiome (or gut flora)—the naturally occurring beneficial bacteria and fungi that assist with proper digestion.1

When we’re stressed, we do not properly digest foods. A stress response produces increased levels of cortisol. Cortisol release is a hormonal protective mechanism, supplying us with the ability to run from the proverbial lion. But while locked into this stress pattern, the body redirects our energy, sacrificing digestion. The body turns off the hydrochloric acid (HCL) that is so important for digesting foods and breaking them into smaller particles.2,3

The HCL acts like a gatekeeper, deterring intruders such as parasites, toxins, and large food particles from entering further down the gastrointestinal system. Without enough HCL for digestion, a breakdown in digestive communication also begins. Signals for digestive enzyme releases go awry, as do signals for shunting the esophageal valves, which results in reflux. When the HCL gatekeeper slacks off, the intruders break through.

This impairs absorption and metabolism, which increases susceptibility to illness and infections. This stress-induced negative feedback loop of immune and inflammatory response further aggravates the intestinal barrier. Inflammation damages the tissue and the tight junctions, the cells of the intestinal tract.4 If you think about this, when the sulcus gets inflamed, it pulls away from the tooth, allowing debris and bacteria to accumulate in the sulcus. The gut acts similarly. The same process happens, except its cells pull apart and allow more food, debris, and toxins to leach into the bloodstream.1

These changes enhance endotoxins such as lipopolysaccharides, which, in turn, increase the body’s load, thereby intensifying development of obesity, depression, joint inflammation, insulin resistance, and other metabolic diseases. Diets low in fiber also contribute to this issue.1,2 Gluten, dairy, alcohol, and sugars have also been known to cause inflammation.

How can you change your diet to prevent leaky gut?

Diet should be the first thing we address when trying to prevent leaky gut.5,6 Following an anti-inflammatory diet is imperative. There are a few plans helpful for eliminating inflammatory foods: the elimination diet, autoimmune paleo diet (AIP), paleo diet, and modified Mediterranean diet.

These diets all eliminate gluten, dairy, alcohol, sugar, and processed foods, which can cause inflammation. AIP also removes a few other common inflammatory foods, such as nightshades, corn, soy, legumes, and nuts. This diet is very restrictive and usually results in lower inflammation, especially for arthritis sufferers.

What foods do you need to avoid?

Diets high in sugar, saturated fats, and low in fiber should be avoided. And let’s not forget about processed foods. Fast foods are not so convenient in the long run when they wreck your health. We must make time for doctors’ appointments to figure out why our mystery symptoms aren’t going away.

Fast foods are loaded with higher levels of fats, preservatives, sodium, and synthetic chemicals. Take french fries, for example. Did you know that some convenient fast-food fries have 14 ingredients? Yes, 14. Fries should be a potato, oil, and maybe a little salt—not 14 ingredients. Do you really know what you’re eating when you consume fast foods?

Is there some kind of test for identifying leaky gut?

In our world of functional medicine, we say test and don’t guess. Yes, there is testing available to see what is going on in the gastrointestinal tract. It is important to help patients find the root causes of their illness and reverse engineer them back to health. 

Editor's note:This article appeared in the May 2022 print edition of RDH magazine. Dental hygienists in North America are eligible for a complimentary print subscription. Sign up here.


  1. Bischoff SC, Barbara G, Buurman W, et al. Intestinal permeability—a new target for disease prevention and therapy. BMC Gastroenterol. 2014;14(1):1-25. doi:10.1186/s12876-014-0189-7
  2. Karl JP, Margolis LM, Madslien EH, et al. Changes in intestinal microbiota composition and metabolism coincide with increased intestinal permeability in young adults under prolonged physiological stress. Am J Physiol Gastrointest Liver Physiol. 2017;312(6):G559-G571. doi:10.1152/ajpgi.00066.2017
  3. Vanuytsel T, van Wanrooy S, Vanheel H, et al. Psychological stress and corticotropin-releasing hormone increase intestinal permeability in humans by a mast cell-dependent mechanism. Gut. 2014;63(8):1293-1299. doi:10.1136/gutjnl-2013-305690
  4. Ménard S, Cerf-Bensussan N, Heyman M. Multiple facets of intestinal permeability and epithelial handling of dietary antigens. Mucosal Immunol. 2010;3(3):247-259. doi:10.1038/mi.2010.5
  5. Choct M. Managing gut health through nutrition. Br Poult Sci. 2009;50(1):9-15. doi:10.1080/00071660802538632
  6. David LA, Maurice CF, Carmody RN, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014;505(7484):559-563. doi:10.1038/nature12820