What Causes Leaky Gut? + What To Eat & Avoid To Help Manage It, From Experts

The terms leaky gut and leaky gut syndrome (sometimes called intestinal permeability) are used with a lot more frequency these days—especially in reference to patients who suffer from painful digestive conditions, like irritable bowel syndrome (IBS) or celiac disease.

While leaky gut is not a widely recognized medical condition yet, more research is starting to emerge to support the idea that you can manage your digestive woes by changing your diet and lifestyle.

At the most basic level, a leaky gut means your intestines aren't quite as secure as they should be.

Here's a quick biology lesson: The walls of the intestines are supposed to be permeable to a degree. This is how the nutrients from the food we eat make it into the body, while other parts of food we can't use continue through the intestines and eventually leave as waste. Ideally, the barrier of the intestines would only allow tiny nutrients to absorb into the bloodstream, and excrete unwanted particles.

The problem occurs when the intestinal tight junctions1—the spaces between the single layer of cells that regulate what enters the bloodstream—are injured (which can happen for a variety of reasons like poor diet and stress). This allows unwanted microbes and undigested food particles to "leak" into the bloodstream, where the immune system often marks them as foreign invaders and attacks. This is considered leaky gut, or increased intestinal permeability2.

Increased intestinal permeability is known to play a role in some gastrointestinal conditions, like celiac disease, Crohn's disease3, and irritable bowel syndrome (IBS)4. While scientists are in agreement that increased intestinal permeability is related to these gastrointestinal issues, it's not clear whether leaky gut is the cause or a side effect of them.

Other studies suggest leaky gut may be connected to autoimmune diseases5, such as arthritis and thyroid disorders.

"Mainstream medicine once considered leaky gut syndrome a fake diagnosis given by alternative doctors. But today, research is confirming that increased intestinal permeability is indeed a major factor in chronic and autoimmune diseases," functional nutrition expert, Will Cole, D.C., IFMCP, tells mbg.

So, what causes increased intestinal permeability? A 2013 study points toward zonulin6, 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.

According to research, bacteria and gluten6 have been shown to trigger the release of zonulin in the small intestine. This is why many functional nutrition experts suggest dietary changes, like a gluten-free diet, to help manage the symptoms.

Other factors that may7 7contribute to a leaky gut7 include medications, like non-steroidal anti-inflammatory drugs (NSAID), antibiotics, stress, and environmental factors. However, there's still no definite cause of leaky gut.

If you think you may have leaky gut, mbg Collective member and gut health expert Vincent Pedre, M.D., recommends working with a registered dietitian or gastroenterologist to begin limiting the following foods from your diet.

While many of these foods have nutritional value on their own, thoughtfully eliminating and slowly reintroducing them to your diet, may help you detect which foods you are more or less sensitive to.

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."

Here: a definitive list of what to eat and avoid on a gluten-free diet.

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 feed bad bacteria8 in the gut.

Dairy products, like milk, cheese, ice cream, and butter, can be notoriously difficult to digest. In fact, about 65% of the human population struggles with lactose intolerance—meaning, they don't have enough of the enzyme (lactase) needed to properly break down lactose. This can lead to gastrointestinal distress.

Soy and its derivatives can be found in everything from tofu to edamame, protein bars, and even some nutritional supplements. While soy in and of itself can be a nutrient-dense ingredient, soybeans are often grown with pesticides, like glyphosate9, which may lead to gastrointestinal issues.10

In people with celiac disease, research suggests corn may trigger similar symptoms as gluten11. Like gluten and soy, corn is present in many packaged foods, so it's important to read labels carefully. (Plus, more than 90% of the corn grown in the United States is reportedly genetically modified.)

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.

Now that you know what not to eat, you might be thinking: so, what's left? Don't worry, there's plenty!

"Focus on clean ingredients with easy-to-digest foods that are low in fructose and sugar and devoid of any substances, including sugar alcohols and pesticides, that are hard on the gut," Pedre suggests. To be more specific, here is a list with the basic components of a gut-friendly diet:

Go for quality fat sources like nuts, seeds, avocado, olive oil, and coconut oil. Skip ultra-refined vegetable oils, like corn and soybean, which may promote inflammation.

These include non-starchy vegetables—think: leafy greens and cruciferous vegetables, such as arugula, broccoli, Brussels sprouts, cabbage, cauliflower, and collard greens. These are a great source of prebiotic fiber, which are essential for feeding probiotic bacteria and nourishing a healthy gut microbiome.

Slow carbs include starchy vegetables, such as sweet potatoes and butternut squash; fiber-rich, low-sugar fruits, like apples and berries; and minimally processed, fiber-rich grains, like rolled oats.

According to Pedre, these include pea, rice, hemp, and chia seeds. Many people with leaky gut seem to be prone to food allergies and sensitivities, as well, so opting for hypoallergenic proteins 12when possible may be beneficial.

Compared to their conventional counterparts, free-range poultry, wild-caught fish, and grass-fed meats contain healthier concentrations of omega-3 fats, which are anti-inflammatory.

The gelatin in bone broth protects the mucosal lining of the digestive tract and helps aid in the digestion of nutrients. Some research suggests collagen peptides may have a similar benefit. Bone broth is also a rich source of glutamine, an amino acid that's a preferred source of energy for the cells of the small bowel, along with other immune cells. It's also been shown to regulate intestinal permeability13.

If you're looking for a plant-based alternative, galangal broth (a traditional Chinese medicine remedy) may also support the gut.

Foods like kimchi, unpasteurized sauerkraut, and lacto-fermented pickles are all rich sources of probiotics that help keep your immune system strong, fend off pathogens, and protect the gut lining.

Important note: If you suspect your leaky gut is caused by IBS, or if your symptoms don't improve when eating the foods suggested above, opting for a low-FODMAP plan may be more beneficial.

Altering your dietary intake should be the first step after visiting a doctor. To further support your gut, consider the following:

Add a probiotic supplement: Good gut bacteria, which are crucial in supporting a healthy microbiome, can become depleted or disrupted by a number of things, and fermented foods may not deliver the amount you need. So, taking a highly concentrated probiotic daily may provide additional support.*

This sample menu incorporates the gut-friendly foods from the list of "what to eat." It's not hard and fast, though—feel free to swap in foods from the list above if you don't have some of these ingredients on hand. The goal is to avoid possibly aggravating foods from the "foods to avoid" list.

Breakfast: A couple of scrambled eggs with a side of sautéed kale. Pro tip: Cooked veggies are gentler on the gut and may be a better choice than raw.

Alternative breakfast option: Go for a bowl of oatmeal with almond milk, berries, and walnuts if you're craving something sweet.

Lunch: A salad with lentils and lean protein will provide sustained energy and a good dose of prebiotic fiber. Add some kimchi or sauerkraut for a probiotic boost.

Alternative lunch: Not a fan of salads? Scoop some tuna or chicken salad (made with an avocado-oil-based mayo) into romaine lettuce and eat it like a taco.

Snack: Carrot slices with hummus, apple slices with almond butter, or crunchy roasted chickpeas. The possibilities are endless, but leaky-gut-friendly snacks should include a form of fiber, along with a bit of fat and protein to help balance blood sugar and keep you fuller, longer.

Dinner: Pan-seared salmon, roasted sweet potato, and Brussels sprouts cooked in olive oil is a delicious, gut-friendly dinner. Whatever you choose to make, keep this simple formula in mind: quality protein source + non-starchy veggie + starchy veggie (optional) + healthy fat.

Alternative dinner: Grilled chicken, zucchini noodles with pesto, and sun-dried tomatoes.

Leaky gut syndrome is a condition in which the cellular junctions of the intestinal wall become damaged, allowing undigested food and bacteria to "leak" into the bloodstream. Leaky gut has been implicated in many autoimmune disorders like IBS and celiac disease. However, it is not yet a widely recognized medical condition and more research is needed to understand the cause and proper treatment methods.

Although leaky gut syndrome is not well understood, there is evidence that a "leaky gut diet" can help alleviate symptoms. Avoiding gluten, dairy, sugar, and other common irritants, while focusing on healthy fats, fermented foods, probiotic supplements, and lifestyle factors can help support the gut.*