Leaky gut, also called increased intestinal permeability, is somewhat new and most of the research occurs in the non-clinical sciences. Leaky gut syndrome is a theory that intestinal permeability is not only a symptom of gastrointestinal disease but an underlying cause that develops independently. Intestinal permeability is a term describing the control of material passing from inside the gastrointestinal tract through the cells lining the gut wall, into the rest of the body. If your intestinal barrier is impaired and the permeability increases (leaky), it may be letting toxins into your bloodstream. These toxins may trigger an inflammatory response that may manifest as various diseases. Unfortunately, some popular foods that you may be eating can cause a leaky gut.
What Causes Intestinal Permeability?
So, what causes increased intestinal permeability? Research points toward zonulin, a human protein that researchers described as “the only known…modulator of intercellular [tight junctions] described so far.” When zonulin is released, the tight junctions of the intestines can break apart . Moreover, certain bacteria and gluten have been shown to trigger the release of zonulin in the small intestine. In turn, this is why many functional nutrition experts suggest dietary changes, like a gluten-free diet, to help manage the symptoms. Other factors that may contribute to a leaky gut include medications, like non-steroidal anti-inflammatory drugs (NSAID), antibiotics, stress, and environmental factors. However, there’s still no definite cause of leaky gut .
While there are a number of potential causes of leaky gut, our diet is actually a major contributing factor. Below is a description of some of the major foods and food categories that could lead to leaky gut.
Certain Dietary Causes of a Leaky Gut
There are a variety of foods that may contribute to leaky gut syndrome for a variety of reasons from impairing digestion, contributing to an imbalance in our good and bad gut bacteria, and more.
Foods that Contain Gluten
Because gluten is linked to the release of zonulin, it’s suspected to trigger leaky gut. Gluten is protein found in wheat, barley, and rye, and common sources include pastas, noodles, breads, pastries, cereal, and granola, not specifically labeled “gluten-free.”
- All wheat derivatives (whole wheat bread, all-purpose flour, wheat pasta, etc.)
- Barley (and malt)
- Oats not labeled gluten-free
Foods High in Sugar
This includes refined sugars, like high-fructose corn syrup, as well as some alternative sweeteners, and alcoholic beverages (which may break down as sugar). Studies have shown that a high intake of sugar can be inflammatory and may enhance some of the bad bacteria (like Proteobacteria) and decrease some of the good bacteria (like Bacteroidetes) in the gut .
- Baked goods like cookies, cakes, pastries
- High carb vegetables
- High carb fruits
Foods High in Lectins
Lectins are found in all gluten-containing grains. They are also found in beans, corn, and nightshade vegetables like tomatoes, eggplant, peppers, and potatoes. Lectins may bind to the cells lining your intestines, disrupting the tight junctions between the intestinal cells, contributing to leaky gut. If you’re struggling with symptoms of leaky gut, it may be helpful to scale back on these foods and see if symptoms improve.
- Wheat based products
Food Contaminated with Mycotoxins
Studies show that mycotoxins cause leaky gut by attacking all four aspects of intestinal protection, including mucosal (physical), chemical, immunological, and microbial barriers .
- Coffee beans
- Dried fruit
- Beer and wine
Vegetable oils are highly processed industrial products that are bad for your gut. Most vegetable oils are made from GMO crops that are engineered to contain extra high levels of lectins in order to resist pests.
- Corn oil
- Soybean oil
- Sunflower oil
- Safflower Oil
- Canola oil
Processed Foods with a lot of Preservatives and Artificial Sweeteners
Boxed and packaged foods are full of preservatives, additives, artificial sweeteners, manufactured sugars like high-fructose corn syrup and more. All of these can contribute to an imbalance in the good and bad bacteria in our gut and exacerbate symptoms of leaky gut syndrome.
Using Best Judgement with Diet Choices
While it would be extremely difficult for any of us to completely eliminate all of the above-mentioned foods or categories of foods, using your best judgement and consuming these foods in moderation is probably the best way to go. There are some foods that are listed in multiple categories above, so those may be a good place to start when it comes to limiting consumption. Focus on clean ingredients with easy-to-digest foods that are low in fructose and sugar and devoid of any substances that are hard on the gut like sugar, alcohols and pesticides. Nutrient-dense foods like quality red meat, poultry, and seafood are a good place to start, but again, moderation is important as too much of these can lead to other health issues. However, for those that do have symptoms of leaky gut or any other gastrointestinal disorder, consulting your doctor is highly advised as some of these foods may need to be completely removed from your diet to alleviate or improve your symptoms. To understand more about the benefits of adding a probiotic or other supplement to your diet, read our article about the best probiotics and supplements for gut health.
-  Fasano A. (2012). Zonulin, regulation of tight junctions, and autoimmune diseases. Annals of the New York Academy of Sciences, 1258(1), 25–33. https://doi.org/10.1111/j.1749-6632.2012.06538.x
-  Camilleri M. (2019). Leaky gut: mechanisms, measurement and clinical implications in humans. Gut, 68(8), 1516–1526. https://doi.org/10.1136/gutjnl-2019-318427
-  Satokari R. (2020). High Intake of Sugar and the Balance between Pro- and Anti-Inflammatory Gut Bacteria. Nutrients, 12(5), 1348. https://doi.org/10.3390/nu12051348
-  Gao, Y., Meng, L., Liu, H., Wang, J., & Zheng, N. (2020). The Compromised Intestinal Barrier Induced by Mycotoxins. Toxins, 12(10), 619. https://doi.org/10.3390/toxins12100619