July 20, 2025, 3:20 pm | Read time: 15 minutes

What is Leaky Gut?

“Leaky Gut” means “permeable gut”: It is characterized by a disruption in the barrier function and thus the protective function due to the permeability of the gut, allowing toxins, allergens, some bacteria, insufficiently digested food components, and harmful microorganisms to enter the bloodstream. This is believed to increase the risk of developing various complaints and diseases.

How was it discovered?

In the 1970s and 80s, a sugar test (lactulose/mannitol) objectively demonstrated that the intestinal barrier can “leak.” In 1985, rheumatologist Michael Smith showed that patients with ankylosing spondylitis have a significantly increased permeability of the intestinal mucosa.¹ Similar “leak” evidence was found in the intestinal walls of Crohn’s disease patients.² U.S. biochemist Jeffrey Bland popularized the term “Leaky Gut Syndrome” in alternative and nutritional medicine.³ In the 2000s, Alessio Fasano provided links to celiac disease and type 1 diabetes through the discovery of the protein zonulin, which regulates the permeability of the intestinal wall.⁴ For many other diseases (such as depression, autism), causal evidence remains thin. The mentioned sugar test is still considered the method of choice for diagnosing a leaky gut.

What does the research say today?

It is scientifically undisputed that the gut can be permeable. In celiac disease, chronic inflammatory bowel diseases (IBD), type 1 diabetes, rheumatic, and metabolic diseases, increased gut permeability is regularly observed.

Alternative Medicine

Alternative medicine practitioners focus on acute digestive complaints, but especially on possible secondary conditions of Leaky Gut triggered by the permeability of the gut. In this context, symptoms, side effects, and secondary conditions related to impaired immune function are particularly noteworthy.

Conventional Medicine

Although classical gastroenterological societies have not yet published independent guidelines on Leaky Gut, recent publications emphasize that the intestinal barrier is essential not only against digestive tract diseases but also for general health.

Whether and to what extent a permeable gut actually leads to autoimmune diseases, allergies, and other complaints is still unclear to many researchers. Especially in chronic bowel inflammation and allergies or intolerances to certain food components, the causes need to be researched more intensively.^5,6,7 Scientific evidence is still needed for the assumption that a permeable gut leads to diabetes, non-dietary allergies, rheumatism, or multiple sclerosis.^8,9,10

Still Unclear

It is also unclear whether Leaky Gut is a cause or a consequence of diseases.¹¹

Impact on the Immune System

Once unwanted substances enter the bloodstream due to a leaky gut, the so-called intestinal immune system is activated. It consists of immune cells such as B cells, T cells, and natural killer cells.

The increased, inherently sensible alertness of the immune system leads to irritation of the intestinal mucosa. The irritated intestinal cells, in turn, trigger unpleasant symptoms due to inflammatory processes. The symptoms resemble those of irritable bowel syndrome.

Also interesting: Causes, symptoms, and treatment of irritable bowel syndrome

Symptoms and Possible Secondary Conditions

The acute complaints associated with Leaky Gut initially relate to the gastrointestinal tract. Additionally, a leaky gut can lead to fatigue and increased susceptibility to infections due to a weakened immune function.

Skin inflammations, muscle cramps, and hair loss are associated with impaired nutrient absorption in the irritated gut. Lastly, the uncontrolled transfer of antigens (substances unknown to the immune system) from the gut into the bloodstream is believed to increase the risk of food allergies and intolerances.

Possible Symptoms and Secondary Conditions of Leaky Gut Syndrome at a Glance

• (Food) Allergies
• Food intolerances
• Autoimmune diseases
• Abdominal pain, diarrhea & bloating
• Hair loss
• Skin inflammations
• Muscle cramps
• Diabetes mellitus
• Multiple sclerosis
• Fatigue
• Increased susceptibility to infections
• Rheumatoid arthritis (inflamed joints)
• Asthma
• Migraine
• Lupus erythematosus (butterfly rash)
• Joint and muscle pain

Food Intolerances Due to Leaky Gut?

In addition to reduced immune defenses and gastrointestinal complaints, it is debated to what extent the increased activity of the immune defense due to the permeable intestinal wall may also promote food allergies and intolerances.

It is suspected that the increased permeability of the intestinal wall reprograms the immune defense. Due to this misprogramming, the immune system increasingly views the body’s own substances or foods that were previously well-tolerated as enemies–triggering intolerances.

Also interesting: How harmful is junk food for gut flora?

Causes of a Permeable Gut

The barrier function of the intestinal mucosa can be weakened by various factors. Intestinal cells react sensitively to allergens, inflammation, toxins such as cell poisons (including alcohol, medications), stress, and environmental toxins.

Some scientific studies have observed that various factors actually make the intestinal mucosa more permeable. These include chronic inflammatory bowel diseases (IBD), celiac disease, irritable bowel syndrome, and food allergies.¹² Chronic alcohol abuse and painkillers containing acetylsalicylic acid or ibuprofen, which have anti-inflammatory effects, can also increase intestinal permeability by weakening the cells of the small intestine wall.^13,14

10 Possible Causes of Leaky Gut Syndrome

Chronic Inflammatory Bowel Diseases

As a result of inflammatory processes from Crohn’s disease or ulcerative colitis, the mucosal cells are damaged, and the gut’s protective function is reduced.

Medications

Antibiotics and painkillers can irritate the mucosa of the stomach and intestines and are also suspected of promoting a leaky gut.

Alcohol

Cell poisons like alcohol can directly damage the intestinal mucosa and reduce the intestinal barrier.

Unhealthy Diet

Sugar, starchy white flour products, preserved foods, and processed foods with an extra portion of additives and unhealthy trans fats can promote inflammatory processes in the gut. An overall high intake of energy, carbohydrates, and fat is also believed to increase gut permeability.

Gluten Intolerance

In gluten intolerance, the immune system overreacts to gluten or wheat protein, reducing the intestinal barrier. Additionally, gluten is criticized for irritating the intestinal mucosa even in healthy individuals.

Lactose Intolerance

In lactose intolerance, damage to the intestines can also increase gut permeability.

Chronic Stress

Since prolonged psychological stress negatively affects natural defenses, ongoing worries, stress, and other burdens are associated with a reduced protective function of the gut.

Infections

Bacteria and viruses such as salmonella or noroviruses, which cause diarrhea, are also potential causes of Leaky Gut.

Pancreatic Diseases

Pancreatic inflammations are also a possible cause of impaired barrier function of intestinal cells.

Impaired Immune System

The majority of our natural defenses reside in the gut. A deficiency in certain components of the intestinal immune system can lead to a reduced immune response and protective function of the intestinal wall. The same applies to a disturbance of the defenses due to small intestine bacterial overgrowth, following radiation therapy, and in HIV or AIDS.

Diagnostic Methods

If you suspect you have Leaky Gut, you should first reflect on your eating habits and lifestyle and possibly change your diet. If there is no improvement, in addition to a self-test, there is the option of obtaining a diagnosis from a specialized conventional or alternative medicine practitioner.

Especially with pre-existing conditions such as food intolerances and autoimmune diseases, a possible involvement of Leaky Gut Syndrome should be confirmed or ruled out through appropriate examinations.

Lactulose-Mannitol Test

The method of choice for diagnosis is a sugar test called the “Lactulose-Mannitol Test.” After drinking a special solution, urine is tested for lactulose and mannitol. If these substances are excreted in increased amounts through the kidneys, a disturbance of the intestinal barrier is suspected.

Additionally, stool tests are offered, in which inflammation parameters and the content of yeasts and lactic acid bacteria are checked. If the protein zonulin (which regulates the permeability of the intestinal wall) is elevated in a blood test, Leaky Gut, diabetes, celiac disease, or a disturbed gut flora may be the cause.

Therapeutic Approaches: Diet and Lifestyle for Leaky Gut

Our dietary tips aim to regenerate the intestinal mucosa, reduce inflammatory processes, and strengthen the barrier function of the intestinal wall and gut flora. A plant-based, carbohydrate-moderate, and low-sugar diet with plenty of fresh food instead of processed products is fundamentally suitable–including an extra portion of probiotics in the form of lactobacilli and bifidobacteria from natural yogurt and the like.

Also interesting: The 8 best probiotic foods for a gut-friendly diet

Avoiding Gluten

Gluten plays a key role among the triggers for increased gut permeability: Especially from the perspective of alternative medicine, wheat protein is repeatedly suspected of triggering and exacerbating the symptoms of Leaky Gut–and not just in diagnosed gluten intolerance.

From a scientific perspective, it is only clear that the immune system forms antibodies against protein components of gluten in diagnosed gluten intolerance such as celiac disease. When these come into contact with the intestinal mucosa, the antibodies trigger an immune response. The unwanted consequence: Inflammatory cells stimulate inflammatory processes in the gut, increase the permeability of the intestinal wall, and can reduce the supply of micronutrients.
Therefore, affected individuals must avoid even traces of gluten. Whether it is also advisable to avoid or reduce gluten intake in Leaky Gut Syndrome is controversial.

Tips: To reduce the permeability of the inflamed gut and regenerate the intestinal mucosa, the individual causes must first be identified. In addition to a generally healthy lifestyle with stress reduction, smoking cessation, and low alcohol consumption, a dietary change to healthy, low-sugar food from fresh ingredients instead of industrial products is recommended.

The following dietary tips should be tested individually, with recommendations such as low-sugar food, fresh food instead of processed products, and omega-3 fatty acids being generally valid. Cell-protecting antioxidants from green leafy vegetables or blueberries and anti-inflammatory spices like turmeric should also be part of the diet. The same applies to steamed or boiled broccoli, Brussels sprouts, and other cabbage varieties if tolerated.

Recommended Foods for Leaky Gut

• Vitamin- and mineral-rich fresh food
• Omega-3 fatty acids (including flaxseed oil, walnuts, salmon)
• Fresh herbs
• Sprouted grains, seeds & nuts
• Avocado & green leafy vegetables
• Bitter substances (including artichoke & chicory)
• Regular consumption of probiotic cultures
• Antioxidants*
• Cabbage vegetables like broccoli
• Adequate fiber
• Turmeric**
• Bone broth***
• Coconut products****

* Cell-protecting and anti-inflammatory antioxidants (secondary plant compounds) from blueberries, carrots, spinach, matcha, and the like.
** Turmeric is considered intensely anti-inflammatory–especially when combined with pepper
*** Bone broth is celebrated by Leaky Gut advocates as a superfood for the gut, as the collagen it contains is said to increase the firmness and structure of the intestinal wall
**** From a nutritional science perspective, flaxseed oil, walnuts, and rapeseed oil play a much more important role in inflammatory diseases

Foods to Avoid with Leaky Gut

• Refined sugar
• FODMAPs*
• Spicy spices
• Processed foods & additives
• Gluten
• Sausage or processed meat
• Sugary, lactose-rich dairy products**
• Preservatives
• (Excessive) alcohol
• (Genetically modified) soy***

* Specific types of sugars and sugar alcohols suspected of increasing gut permeability (see next paragraph)
** Whether lactose is tolerated varies individually
*** Test individual tolerance and buy organic soy, as it is free from genetic engineering

Avoiding FODMAPs

In recent years, interest in irritable bowel syndrome, chronic inflammatory bowel diseases, and other digestive disorders has increased significantly. FODMAPs stands for fermentable oligo-, di-, monosaccharides, and polyols, or fermentable multiple, double, and simple sugars, as well as polyols (sugar alcohols). Since these food components from cabbage, white flour products, legumes, and the like are not usable by the body, they are partially fermented by the gut flora, leading to bloating, among other things. Gluten-containing grain products are also among the FODMAPs.

From a nutritional science perspective, it is still unclear whether FODMAPs also increase gut permeability and promote inflammatory processes. Nevertheless, avoiding them is increasingly adopted by irritable bowel patients and people with chronic inflammatory bowel diseases, as the well-being of many affected individuals improves.

Therefore, it is suspected that people with Leaky Gut may also benefit from avoiding FODMAP-rich foods. However, many valuable foods like broccoli, garlic, and onions are included, so they should be tested individually.

Probiotic Diet for a Permeable Gut

When it comes to gut health–and accordingly supporting natural defenses–probiotic cultures are essential. These primarily include lactic acid found in fermented dairy products and vegetables. While a positive influence on gut flora and the natural barrier function of the gut is considered likely, it is still unclear whether probiotics actually improve the symptoms of Leaky Gut Syndrome.

Probiotics at a Glance

• Natural yogurt
• Kefir
• Fresh sauerkraut (unheated)
• Miso
• Tempeh
• Specially enriched drinking yogurts
• Fresh pickles (unheated)
• Kombucha
• Other lactic acid-fermented vegetables

Also interesting: Ayurveda expert: “Reprogramming your gut leads to healthier eating and weight loss!”

Criticism of Expensive Leaky Gut Products

Criticism is mainly directed at the commercialization of gut health without a solid scientific basis. It is criticized that Leaky Gut Syndrome is marketed on a large scale and aggressively with high-priced dietary supplements for gut restoration. Numerous offers can be found online, which are recommended for a permeable gut: “Leaky Gut” or “detox packages,” tablets that are supposed to “reduce inflammation flare-ups in Leaky Gut.” These products usually contain sodium butyrate, dextrose powder, or zeolite. Zeolite, for example, is supposed to bind toxins to the intestinal mucosa as a surface substance–just like healing clay.

The EU, for example, sees no sufficient scientific evidence for the health effects of these substances. Accordingly, there are no approved health claims for zeolite, healing clay, and the like under EU regulation. This means that manufacturers are not allowed to advertise with such claims. However, in reality, this often looks quite different…

For those interested in the topic: In the official “Health Claim” register of the European Food Safety Authority, you can search for ingredients and immediately see whether a health claim has been submitted, rejected, or approved.

More on the topic

Nutrition The 8 Best Probiotic Foods for a Gut-Friendly Diet

According to a Study Dairy Products Are Good for the Gut — Apparently with One Exception

Developed by Scientists How the Restore Diet Works — and Which Diseases It Prevents

Conclusion

Leaky Gut Syndrome describes a disrupted intestinal barrier through which unwanted substances can enter the body–with potential consequences for the immune system, digestion, and overall health. It is medically undisputed that the intestinal mucosa can be permeable–and documented in certain conditions such as irritable bowel syndrome, chronic inflammatory bowel diseases (IBD), or type 1 diabetes. There is no reliable evidence yet that a permeable gut reliably leads to allergies, headaches, and many other health problems and nonspecific symptoms. Undisputed: Gut health responds to diet, exercise, and infections. Against this background, it is highly advisable to eat anti-inflammatory foods and strengthen the microbiome with the right foods–instead of irritating it with the wrong ones. If you suspect Leaky Gut Syndrome, you should see a gastroenterologist.