Evidence Based
4.8 /5
21

Understanding Leaky Gut + Causes & Ways To Improve

Written by Biljana Novkovic, PhD | Last updated:
Nattha Wannissorn
Puya Yazdi
Medically reviewed by
Nattha Wannissorn, PhD, Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

SelfHacked has the strictest sourcing guidelines in the health industry and we almost exclusively link to medically peer-reviewed studies, usually on PubMed. We believe that the most accurate information is found directly in the scientific source.

We are dedicated to providing the most scientifically valid, unbiased, and comprehensive information on any given topic.

Our team comprises of trained MDs, PhDs, pharmacists, qualified scientists, and certified health and wellness specialists.

All of our content is written by scientists and people with a strong science background.

Our science team is put through the strictest vetting process in the health industry and we often reject applicants who have written articles for many of the largest health websites that are deemed trustworthy. Our science team must pass long technical science tests, difficult logical reasoning and reading comprehension tests. They are continually monitored by our internal peer-review process and if we see anyone making material science errors, we don't let them write for us again.

Our goal is to not have a single piece of inaccurate information on this website. If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please leave a comment or contact us at [email protected]

Note that each number in parentheses [1, 2, 3, etc.] is a clickable link to peer-reviewed scientific studies. A plus sign next to the number “[1+, 2+, etc...]” means that the information is found within the full scientific study rather than the abstract.

‘Leaky gut’ is gaining more attention by the day, although it is not a recognized medical condition. This is because studies are increasingly associating various diseases with the state of our gut. Increased intestinal permeability, also known as ‘leaky gut,’ has been linked to autoimmune diseases, chronic fatigue syndrome, allergies, and even depression. In this post, you will learn more about the intestinal barrier, factors that may disrupt it, and ways in which you can improve your gut health.

What is the Intestinal Barrier?

The main function of the gut is to absorb nutrients from food. However, the gut also has another important function – to keep harmful things such as bacteria (good as well as bad), toxins, and food antigens (inflammatory agents) out and away from the rest of the body [1].

The intestinal barrier basically separates the gut content from the body. It is made of a single layer of cells (epithelial cells, sensing cells, and cells that produce enzymes and neurotransmitters).

These cells are linked by tight junction (TJ) proteins [1].

The intestinal/gut barrier is amazing! It [2]:

  • covers a surface of about 400 m2
  • uses approximately 40% of the body’s energy expenditure
  • is renewed approximately every 5 days

Research suggests that many other factors help support this barrier [1]:

  • Mucus
  • Beneficial gut bacteria
  • Antimicrobial molecules
  • Immunoglobulins (especially IgA)
  • Cytokines

Studies have found that gut bacteria, in particular, have many beneficial roles in maintaining the intestinal barrier. They [1]:

  • Help with the digestion and absorption of nutrients
  • Prevent colonization by harmful bacteria
  • Stimulate immunity

What Is Leaky Gut?

Is leaky gut a real issue? Research that’s increasingly accumulating on the subject suggests that it may be. However, leaky gut is not recognized as a legitimate medical issue because, at this point, there is simply not enough evidence to support it.

On one hand, there is a lot that scientists still don’t know or understand about the gut and the microbiome within it. On the other hand, there is a lot of speculation that has been derived from small-scale human or animal studies. In this article, we will try to objectively review the research on this subject.

The theory is fairly simple. When there are abnormalities in the intestinal barrier, the intestinal permeability increases. This potentially means that more of the gut content can pass/leak through, which is referred to as “leaky gut” [1].

Some scientists think that when the gut is leaky, gut bacteria and their products may escape the gut, which could potentially produce inflammation and cause tissue damage. Similarly, food-derived antigens (proteins or partially digested proteins) could pass through the gut and promote both local or whole-body immune responses [1].

On the molecular level, researchers have found zonulin, a protein that causes tight junctions to open. When tight junctions open, intestinal permeability increases. Studies suggest that some agents, such as bacteria and gluten, may be able to cause ‘leaky gut’ by increasing zonulin [3, 4].

Leaky Gut Signs and Symptoms

Proponents of Leaky Gut Syndrome state that if you suffer from leaky gut, you may experience one or more of the signs and symptoms listed below:

  • Bloating
  • Gas
  • Cramps
  • Food sensitivity
  • Pain
  • IBD
  • IBS
  • Autoimmune disease
  • Thyroid problems
  • Skin conditions (inflammatory, acne)

However, none of these symptoms is specific, and they can all have alternative causes. In addition, skeptics stress that leaky gut is likely to be only a symptom of some of the conditions listed above (e.g. IBD) and not a valid medical condition in its own right.

Testing for Intestinal Permeability

There are a couple of tests available that test for intestinal permeability. However, these tests are not recognized by mainstream medicine because there is not enough research to back them up.

The Lactulose-Mannitol Test

This test has been used the longest in both human and animal studies [5].

Lactulose and mannitol are sugars that aren’t broken down in the digestive tract. Mannitol is smaller and gets absorbed through the gut. Lactulose is larger and is only absorbed if there is increased intestinal permeability. Levels of lactulose vs. mannitol can then be measured in the urine [2].

However, there is a question of how reliable this test is. In a study of people with celiac disease, a condition which in theory should go hand in hand with increased intestinal gut permeability, a lactulose-mannitol test was normal for more than half of the 29 patients [6].

In addition, studies suggest that decreased gut flow and impaired kidney function can affect the results. The test is also unsuitable for patients on blood transfusion since mannitol is used in the storage solution of banked blood [2].

If you do decide to take this test, remember to take your result with a grain of salt. A normal result on this test doesn’t mean that you don’t have a medical condition, and similarly, an abnormal result doesn’t mean that you have one.

Zonulin Blood Test

Zonulin is a protein that causes tight junctions to open. Some scientists suggest that more zonulin may mean that there is higher intestinal permeability. They also suggest that zonulin may be a marker for leaky gut and autoimmune diseases that are caused by issues in the zonulin pathway [3, 4].

However, while blood tests for zonulin recently became available, there is not much that we actually know about how useful this test is or what the normal ranges in different populations may be. So it would be best to approach this test as highly investigational.

Food Sensitivity or Antibodies Against Foods

With an intact gut, the immune system should not be exposed to the gut content. Therefore there shouldn’t be a lot of antibodies against foods. By inference, if you have a lot of antibodies against various foods, you likely have some intestinal permeability.

While the logic here seems solid, clinical studies that would show a cause and effect relationship between leaky gut and food sensitivities are missing.

On the plus side, you will likely benefit from knowing which foods you are allergic to, if any.

What Can Increase Gut Permeability?

The section below is based on limited evidence from small-scale human and animal studies. While many of these studies are intriguing, large-scale clinical trials are needed to corroborate their findings!

1) Poor Diet

Animal studies have found that unhealthy diets can create an imbalance in the intestinal barrier. These diets include:

  • Diets low in fiber [1]
  • Diets high in saturated fats [1]
  • Diets high in fats and sugars (a typical Western diet) [2]
  • Diets high in processed food containing emulsifiers [7]

In an observational study that looked at 100 pregnant overweight women, women who ate more healthily (more omega-3 fatty acids, fiber, vitamins, and minerals) tended to have lower intestinal permeability (measured by zonulin) [8].

In mice, a high-fat diet increased gut permeability by reducing the production of tight junction proteins [9].

2) Lectins

Lectins are proteins that are especially concentrated in seeds (grains, legumes, nuts) and tubers (potatoes).

Lectins can be beneficial by stimulating the immune system. However, research suggests they may also bind to the surface of gut-lining cells and disturb the gut barrier [10].

Animal studies suggest that when lectins cause leaky gut, both dietary and bacterial antigens (inflammatory agents) may leak into the blood and activate the immune system [11, 12, 13, 10].

Furthermore, in human gut cells, some dietary sources of lectins such as wheat may directly open tight junctions by increasing zonulin. However, the degree of this created intestinal permeability is much higher in gut cells from people with celiac disease compared to gut cells obtained from healthy people [14].

3) Chronic Stress

Research suggests that stress hormones from the HPA axis, such as CRH, can increase intestinal permeability and cause inflammation [15, 16].

A study in 23 healthy volunteers, showed that stress from giving a public speech, measured as an increase in the stress hormone cortisol, increased gut permeability (via CRH) [17].

Maternal separation and other types of stress increase intestinal permeability in rats [18, 19].

In addition, rats who experienced maternal separation in youth are also more prone to leaky gut when they experience social stress as adults [20]!

4) Injury

A human study in 29 intensive care patients showed that there is increased intestinal permeability 72 to 96 hours after trauma. The more severe the injury, the greater the increase in gut permeability [21].

In the same study, patients with a larger increase in intestinal permeability were at a higher risk of whole-body inflammation, multiple organ dysfunction, and infections [21].

Similarly, studies show that burn injuries increase intestinal permeability in both animals and humans [22].

In an animal study, mice with burn injuries had disturbed microbiota (particularly a deficiency of butyrate-producing bacteria) and increased gut permeability [23].

Research suggests that mice and rats with traumatic brain injuries also have increased intestinal permeability [24, 25].

5) Strenuous Exercise

Exercise may increase intestinal permeability. While we exercise, blood goes into the muscles and away from the stomach, and the supply of oxygen to the gut is reduced.

Studies suggest that when the blood supply to the gut is reduced by more than half, intestinal permeability increases. For reference, people exercising at 70% maximum capacity have a 60 to 70% reduced blood flow to the gut. At 100% of maximum capacity, the blood flow is reduced by 80% [26].

Some scientists think that people who exercise at high intensities for longer periods may have compromised gut barrier integrity. This would put them at a greater risk of chronic inflammation and diseases [27].

In a study of 20 athletes, running at 70% capacity increased intestinal permeability, which is more pronounced in those who already suffered from gut-related symptoms [28].

Cycling at 70% capacity increased gut leakiness and the number of allergens reaching the bloodstream in another study with 10 people [29].

Two studies with 37 and 38 soldiers, respectively, suggest that high-intensity combat training increases gut permeability as well as the incidence and severity of gut-related symptoms [30, 31].

However, a study in 11 well-trained athletes showed that the gut adapted to exercise. As a result, the intestinal permeability was not affected [32].

This suggests the gut barrier may be ‘trained’ akin to training your muscles.

6) Alcohol

Alcohol may disrupt intestinal barrier function and increase gut permeability [33].

A study in 36 alcoholics suggests that alcoholics have higher gut permeability, which can persist for up to 2 weeks after drinking [34].

Another study showed that one week of moderate consumption of red wine was safe in healthy people. However, it increased intestinal permeability in 14 patients with inactive inflammatory bowel disease (IBD) [35].

Some harmful bacteria, including E. coli, produce alcohol. Certain scientists propose that alcohol may be how these bacteria compromise the gut barrier function [36].

7) Bacterial Imbalance (Dysbiosis)

The intestinal barrier acts as a shield that may be modified by gut bacteria [37].

Research suggests that disturbances in the gut microbiota may cause gut barrier dysfunction in various disorders and diseases [37].

In a study of 100 overweight pregnant women, those with leaky gut (higher zonulin) had a lower diversity of gut bacteria [8].

At this point, however, this is all based on association and speculations.

8) Infections

Some harmful bacteria may gain access to the body by altering tight junctions to increase gut permeability [38].

In cell and animal studies, H. pylori directly increase gut permeability by acting on tight junction proteins [39, 40].

Research suggests that other types of infections may also increase intestinal permeability. For example:

  • Patients with malaria may have increased intestinal permeability (measured by a lactulose-mannitol test) [41].
  • Tapeworm parasites can caused leaky gut in rats [42].
  • Candida increased gut permeability in a cell-based study [43].

9) Inflammation

Molecular studies have shown that inflammation may increase intestinal permeability through TNF-alpha, IL-1beta, IFN-gamma, Nf-KB, and other cytokines [44, 45, 46, 47].

10) Drugs, Including NSAIDs

Conventional NSAIDs increase gut permeability in humans within 24 hours of ingestion. This is more evident when these drugs are taken long-term [48, 49, 50, 51, 52].

Stomach acid-suppressing drugs (PPI) may also increase gut permeability based on studies in people with liver cirrhosis [53]. However, there are also studies that show the exact opposite. In 14 patients with cystic fibrosis, PPIs seemed to reduce gut permeability [54].

11) Some Supplements

A study of 28 healthy female volunteers showed that vitamin C may increase intestinal permeability (lactulose-mannitol test) and that this effect may be additive when vitamin C is added to aspirin [55].

However, we don’t know how long-lasting or meaningful this effect is.

Similarly, a study of 153 children showed that iron supplementation can increase intestinal permeability (lactulose-mannitol test) [56].

12) Nutrient Deficiencies

Molecular, cell, and animal studies suggest that zinc plays an important role in maintaining the intestinal barrier [57, 58, 59].

A study in 25 children has found that perturbed zinc balance may be associated with abnormal gut permeability (measured by a lactulose-mannitol test) [60].

Animal studies further suggest that vitamins (especially A and D) are necessary for the proper function of the intestinal barrier:

  • A vitamin A-deficient diet impaired the intestinal barrier in rats [61].
  • Vitamin D-deficient mice were more sensitive to gut barrier disruption [62, 63, 64].

However, additional studies are needed to check if this also applies in humans.

13) Circadian Rhythm Disturbances

Circadian rhythms may be important for the maintenance of the intestinal barrier [65].

An observational study of 22 workers showed that night-shift workers were more prone to alcohol-induced leaky gut compared to day-shift workers [66].

Circadian disruptions, by either genetics or environmental cues, caused leaky gut in mice. These mice were also more susceptible to further gut damage by alcohol [65, 67].

14) Radiation

Exposure to radiation, such as radiation therapy, increases intestinal permeability in humans [68, 69].

In animal studies, radiation rapidly disrupted tight junctions in mice and increased gut permeability in monkeys [70, 71].

15) Chemotherapy

Chemotherapy increases intestinal permeability in humans; however, the exact mechanism is still not fully understood [72, 73, 74, 75].

16) Birth and Infancy

Studies suggest that babies may naturally have a more leaky gut, which allows them to absorb immune substances from their mother’s milk [76].

In addition, research shows that preterm babies have a more leaky gut than full-term babies during the first 2 days of life [76, 77].

17) Formula vs. Breastfeeding

A study with 62 preterm infants showed that those fed mostly human milk (>75%) had lower gut permeability than those receiving either low amounts or no human milk (<25%) (lactulose-mannitol test) [78].

18) Aging

The intestinal barrier may weaken as we age. Research suggests that gut permeability (measured by zonulin) is higher in older people [79].

However, a study with 215 adults suggested that the gut barrier does not deteriorate with age per se. Instead, in that study, it deteriorated due to chronic inflammation and minor diseases that get more common as we age [80].

In 18 elderly people, high gut permeability was associated with higher markers of inflammation: TNF-alpha and IL-6. It was also associated with lower muscle strength and less habitual physical activity [79].

Many different factors have been associated with increased gut permeability, including poor diet, stress, injury, alcohol, infections, some drugs and supplements, and inflammation. However, there is usually only a single or a couple of small-scale low-quality human studies addressing each of these factors. While the prospects are certainly intriguing and promising, large-scale human trials are needed to confirm all of these associations and any potential causal relationships.

Diseases Linked to Leaky Gut

1) Autoimmune Diseases

There are scientists who suggest that a dysfunctional intestinal barrier may be an important cause of autoimmune disorders [1].

They further think that leaky gut may be a source of the whole-body immune activation and Th17/Treg cell imbalance seen in autoimmune diseases [81].

Human and animal studies have found an association between Increased gut permeability and:

  • Type 1 diabetes [82, 83, 84]
  • Autoimmune hepatitis [85, 86]
  • Ankylosing spondylitis [87, 88]
  • Celiac disease [89, 90]
  • Rheumatoid arthritis [91]
  • Lupus [92]

Proponents of this hypothesis point out that less than 10% of the people who are genetically susceptible to autoimmune disease, actually develop a disease. This means that environmental factors are important in autoimmune disease development [93].

In genetically predisposed people, a leaky gut may allow foreign inflammatory agents to enter the body. Then, these agents may trigger the initiation and development of the autoimmune disease [1].

Research suggests that blocking zonulin, a protein that opens tight junctions may help reduce intestinal permeability. It was able to reverse type 1 diabetes in a study with rats [4, 94].

In a clinical trial of 342 celiac disease patients on a gluten-free diet, larazotide, a drug that blocks zonulin, reduced signs and symptoms of celiac disease better than a gluten-free diet alone [95].

2) Inflammatory Bowel Disease (IBD)

Research suggests that people who have inflammatory bowel disease (Crohn’s disease or ulcerative colitis) may have a disrupted intestinal barrier [96, 97].

In a study with 110 patients with IBD, impaired intestinal permeability was associated with ongoing bowel symptoms. Increases in permeability correlated with more severe diarrhea [98].

This increase in intestinal permeability may be partially genetic. A study showed that intestinal permeability was increased in most patients with Crohn’s disease. However, it was also increased in 30% of their healthy relatives (223 healthy subjects) [99].

According to a similar study, the ‘gut leakiness’ in patients with Crohn’s disease and their relatives could be further exacerbated by aspirin [100].

A therapy that blocks TNF-alpha, an inflammation-promoting cytokine, restored intestinal permeability in a study with 23 Crohn’s disease patients [101].

3) Irritable Bowel Syndrome (IBS)

Patients with IBS may also have increased gut permeability [102, 103].

In a small-scale study, when 36 IBS patients with a suspected food intolerance ate the offending food in question, it disrupted their intestinal barrier, as compared to controls, based on microscopic examination [104].

4) Chronic Fatigue Syndrome

Some scientists suggest that Increased gut permeability may be behind the severe fatigue and brain fog in patients with chronic fatigue syndrome [81, 105].

A study of 41 patients with chronic fatigue syndrome showed that more than half of the patients experienced improvement when they took supplements that purportedly help gut barrier function (such as glutamine and zinc) [105].

5) Diseases of the Nervous System

Increased gut permeability has been reported in the following diseases:

At this point, it is not possible to tease apart the cause and the effect in these studies. Gastrointestinal disbalance may precede nervous system disorders and may have a role in the early development of these diseases. On the other hand, increased intestinal permeability could also be only one of the symptoms of these diseases.

6) Depression

A study of 112 people with depression (and 28 controls) showed they depressed people had more antibodies against gut bacteria, suggesting a ‘leaky gut’ [113, 114].

A study of 60 alcoholic subjects found that those who had leaky gut were more prone to depression and anxiety [115].

7) Autism

Some studies (53 patients and 73 controls) showed that intestinal permeability was higher in those with autism [116, 117].

Another study found that both those with autism and their first-degree relatives were more likely to have higher intestinal permeability [118].

However, 2 other studies (140 subjects) found no abnormal intestinal permeability in autistic children [119, 120].

8) Allergies

A study of 41 patients with food allergies or food sensitivities showed that they had increased gut permeability. In fact, those with higher intestinal permeability had more severe allergy symptoms [121].

Research suggests that those with food allergies get a leaky gut after eating trigger foods. However, their gut permeability was also increased at baseline, when they were on elimination diets [122, 123, 121].

A study of 131 allergic children without symptoms on elimination diets showed that about a third had increased gut permeability [124].

9) Asthma

Studies suggest that gut permeability may be higher in people with both allergic and nonallergic asthma [125, 126, 127].

10) Eczema, Psoriasis, and Acne

Some scientists think that increased intestinal permeability may be one of the reasons people experience trouble with acne [128, 129]. More evidence is needed, however, to validate this theory.

In a small study of 15 people, those with psoriasis showed higher intestinal permeability than controls [130].

In another study compromised intestinal barrier was found in 18 people with eczema [131].

11) Obesity

Obese people may have leaky guts. Two studies, one with 40 and one with 55 subjects, showed that those with larger waists and worse metabolic parameters had higher gut permeability [132, 133].

Higher gut permeability was associated with higher BMI, increased inflammation (IL-6), and lower insulin sensitivity in 123 men [134].

12) Diabetes

Leaky gut has been associated with type 2 diabetes in a study that compared 130 people with diabetes and 161 controls [135].

Similarly, another study found a link between increased gut permeability (high zonulin)and pregnancy-induced diabetes in 88 pregnant women [136].

13) Liver Disease

In a study that included 39 children suffering from fatty liver and 21 controls, researchers found that intestinal permeability was increased in children with fatty liver. In addition, those with higher gut permeability tended to have more severe disease symptoms [137].

Research further suggests that patients with liver cirrhosis may also have increased intestinal permeability and intestinal barrier dysfunction [138].

Some scientists think that leaky gut may explain why not all heavy drinkers develop liver injury. They speculate that a leaky gut may be a necessary factor for the development of chronic liver injury among heavy drinkers [139].

14) Obstructive Sleep Apnea

Patients with obstructive sleep apnea (OSA) had a higher risk of having leaky gut in a small study that included 38 OSA patients and 38 controls [140].

15) Cancer

A couple of studies suggest that humans with cancer may have increased intestinal permeability [141, 142].

In cancer-prone mice, a high-fat diet disrupted gap junction proteins, thereby increasing gut permeability. This led to increased inflammation and accelerated the development of tumors [143].

Small-scale human studies have found increased intestinal permeability (leaky gut) in many different medical conditions, from autoimmune and inflammatory disease to obesity and diabetes. However, larger studies are needed to confirm these findings. In addition, well-designed observational studies and clinical trials are needed to tease apart the cause and the effect for each condition. As it is now, there is not enough evidence that leaky gut may cause other non-gut related conditions. We will update the article with new information as soon as it becomes available.

How to Prevent a Leaky Gut

As leaky gut may occur as a symptom in a number of underlying diseases, the most important thing is to work with your doctor to address any potential underlying health condition.

For example, several studies have shown that chronic infections can increase gut permeability, and therefore they need to be addressed if possible [39, 40, 41, 42, 43].

Some clinical studies show that addressing leaky gut may be beneficial in some gut-related conditions such as inflammatory bowel disease (IBD), diarrhea, irritable bowel syndrome (IBS), and celiac disease. However, at this point in time, there is little to no clinical evidence that addressing leaky gut could improve any particular non-gut related condition.

1) Potentially Beneficial Lifestyle and Dietary Changes

Much of the emerging research shows that stress may increase intestinal permeability [15, 16, 17]. Managing stress levels is one way to potentially improve the function of your intestinal barrier and your overall health.

A healthy circadian rhythm may also help keep your gut healthy [65].

Alcohol increases intestinal permeability and is best avoided if you have gut issues [33, 34, 35]. Even moderate consumption can increase intestinal permeability in people who have gut inflammation [144].

If you have certain food sensitivities (e.g. gluten), you may need to avoid offending foods. However, make sure your diet is overall healthy and well balanced, to avoid nutritional deficiencies [2].

2) Moderate Exercise

In 30 people with diabetes who initially had increased intestinal permeability, 6 months of regular exercise improved leaky gut and decreased low-grade inflammation [145].

Swimming increased tight junction protein levels in rats [146].

In mice, 30 minutes of swimming per day maintained low intestinal permeability. It also prevented chronic stress-induced gut barrier dysfunction [147].

3) Vitamins and Minerals

Make sure you are not deficient in vitamins and minerals required for proper gut barrier and immune function. These include vitamin A (retinol), vitamin D, zinc, and B vitamins.

Vitamin A

A clinical trial in 79 children showed that vitamin A lowered intestinal permeability [148].

Vitamin D

Vitamin D helps maintain the intestinal barrier [64, 149, 1].

Vitamin D helped maintain low intestinal permeability in a study with 27 Crohn’s disease patients in remission [150].

Vitamin D also reduced the sensitivity of the intestinal barrier to alcohol in mice [151].

Vitamin B

Niacin (vitamin B3) decreased intestinal permeability in patients with alcohol-induced niacin deficiency [152].

Zinc

Zinc restored intestinal permeability in Crohn’s disease patients, probably by maintaining tight junctions [153, 154].

In 12 Crohn’s disease patients in remission, those receiving zinc (10 patients) had normal gut permeability and did not relapse. Of the remaining 2 who had increased intestinal permeability, 1 relapsed [153].

Low levels of zinc improved intestinal permeability in a study of 58 children with diarrhea [155].

4) Probiotics

Probiotics may help reduce gut leakiness. Some scientists suggest they can strengthen tight junctions and restore the integrity of the intestinal barrier.

In 2 studies with 10 and 7 people, respectively, L. plantarum promoted gut barrier repair and increased the stability of tight junctions [156, 157].

Fermented milk with probiotics decreased gut permeability in a clinical trial with 30 IBS patients [158]. The probiotics included S. thermophilus, L. bulgaricus, L. acidophilus, and B. longum.

The following probiotics have helped improve ‘leaky gut’ in animal and cell studies:

5) Prebiotics/Fiber

Prebiotics are fibers that stimulate the growth of beneficial bacteria in the gut.

Inulin-enriched pasta preserved the intestinal barrier and decreased zonulin in 20 healthy volunteers [174].

In 32 people with fatty liver, a diet high in fiber reduced intestinal permeability and blood zonulin levels and improved liver function [175].

Prebiotic galactooligosaccharides (GOS) improved intestinal barrier function in rats with pancreatitis [176].

Prebiotics lowered intestinal permeability and improved tight-junction integrity in obese and diabetic mice [177].

6) Glutamine

Studies suggest that glutamine may help maintain intestinal barrier function [178].

Glutamine had beneficial effects on intestinal integrity in 101 preterm infants and increased intestinal barrier function in a study with 80 malnourished children [179, 180].

A study of 51 cancer patients showed that glutamine countered the chemotherapy-induced increase in intestinal permeability [181].

Glutamine reduced radiation-caused gut injury and maintained lower gut permeability in rats [182].

7) Other

No clinical evidence supports the use of any of the below-listed foods and supplements for improving gut permeability. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.

  • Fermented foods (barley, soybean, kimchi) decreased gut permeability in mice and rats with IBD-like inflammation [183, 184, 185]
  • Omega-3 acids helped improve gut barrier function in mice with inflammation and after chemotherapy [186, 187]
  • Curcumin improved gut barrier function in rats, mice, and human cells [188, 189, 190, 191].
  • Butyrate helped protect the intestinal barrier in rats with gut inflammation, and in mice fed a high-fat diet or exposed to chemotherapy [192, 193, 194].
  • Melatonin improved gut barrier function in diabetic rats and rats on alcohol and in mice with IBD-like gut inflammation or mice treated with NSAIDs [195, 196, 197, 198, 199].
  • Ginkgo biloba helped restore the gut barrier in rats by restoring tight junctions [200].
  • Lipoic acid supplementation reduced intestinal permeability in post-weaning rats [201].
  • Quercetin protected the intestinal barrier from NSAID-induced damage in rats [202, 203].
  • Sulforaphane, found in high amounts in broccoli sprouts, strengthened the gut barrier in mice [204].

A healthy lifestyle, exercise in moderation, and a balanced diet rich in fiber may help improve gut health.

Genetic Factors That Influence Intestinal Permeability

HLA-DQ2.5 and HLA-DQ8.1

HLA-DQ is a protein found on the surface of cells that communicate with the immune system (it presents antigens to immune cells).

Studies suggest that two variants, HLA-DQ2.5 and HLA-DQ8.1 are associated with about 6-fold higher risk of developing celiac disease. About 98% of people with celiac disease have one or both of these variants [205, 206, 207].

You have HLA-DQ2.5 if you have the following variants:

  • The HLA-DQA1*0501 variant in the HLA-DQA1 gene
  • The HLA-DQB1*0201 variant in the HLA-DQB1 gene

You have HLA-DQ8.1 if you have the following variants:

  • The HLA-DQA1*0301 variant in the HLA-DQA1 gene
  • The HLA-DQB1*0302 variant in the HLA-DQB1 gene

Don’t panic if you have one of these variants. It’s important to stress that up to 40% of the general population has these variants. However, only about 1% go on to develop celiac disease. This indicates that HLA-DQ2.5 and HLA-DQ8.1 variants may be necessary but not sufficient for disease development [208, 207, 209].

Because of this, the primary value of genetic testing is to rule out celiac disease/gluten intolerance. If you are among the 60% of people who do not carry either of these variants, you are unlikely (>95%) to be at risk. That means that you can avoid unnecessary invasive test procedures, such as blood punctures, duodenal biopsies, etc. [209].

Apart from celiac disease, studies suggest that having either HLA-DQ2 or HLA-DQ8 is associated with an increased risk of type 1 diabetes, with a higher risk for people who carry both variants [210, 211].

MYO9B

Myosin IXb (MYO9B) is a protein that helps maintain the intestinal barrier. Based on a study in 1.6k Europeans, these MYO9B variants have been associated with increased intestinal permeability [212]:

Three of these variants have also been associated with IBD: rs1545620, rs1457092, and rs2305764, based on a meta-analysis of 10 studies with 8.9k cases, and 9.4k controls [213].

The rs1545620 and rs2305764 variants have been associated with celiac disease in multiple studies [214, 215, 216, 217]. However, there is also a study that failed to find an association between MYO9B and celiac disease [218].

rs2279003 and rs2305764 have also been linked with type 1 diabetes, while rs1457092 was associated with lupus and rheumatoid arthritis [219, 216].

NOD2/CARD15

NOD2 (also known as CARD15) functions as an “intestinal gatekeeper.” This protein recognizes bacteria, viruses, and parasites, and activates the immune system. It also helps shape our gut microbiota [220].

Based on one study that involved people with Crohn’s disease, their relatives, and healthy controls, these NOD2/CARD15 variants were more often found in people with Crohn’s disease and their relatives [221]:

The same study showed that in healthy relatives of Crohn’s disease patients, 40% of those with the 3020insC and 75% of those with both 3020insC and R702W had increased intestinal permeability [221].

3020insC (either rs2066847 or rs5743293) was also associated with increased permeability in another study with Crohn’s disease patients [222].

JAK2

Janus kinase-2 (JAK2) promotes the growth and division of cells, in response to hormones and cytokines (interferon, erythropoietin, leptin, and growth hormone) [223].

IBD patients carrying the JAK2 rs10758669 (C) variant more often had increased intestinal permeability, based on a study in 464 Crohn’s disease patients, 292 ulcerative colitis patients, and 508 controls [224].

HP

HP is the haptoglobin gene. Haptoglobin binds free hemoglobin in the blood and prevents it from causing oxidative stress and tissue damage. It comes in 2 common variants: Hp1 and Hp2.

It was discovered that prehaptoglobin-2, a precursor of the Hp2 variant, is actually zonulin [225, 226].

Therefore, people with Hp2 variants may have an increased risk of immune and inflammatory disorders due to higher zonulin and increased intestinal permeability [225].

MAGI2, MAGI3, and PARD3

MAGI2, MAGI3, and PARD3 are tight junction proteins.

IBD has been associated with rs6962966 in MAGI2 and rs1343126 in MAGI3 [227].

rs10763976 in PARD3 and rs6962966 in MAGI2 have been associated with both celiac disease and ulcerative colitis [228].

AHR

AHR (aryl hydrocarbon receptor) is a protein that activates detoxification enzymes in response to pollutants and cancer-causing agents. It also plays an important role in activating the immune system [229, 230].

A study suggests that AHR rs7796976 (G) may increase the risk of disturbed intestinal permeability in Crohn’s disease patients. Smoking can exacerbate this effect [231].

About the Author

Biljana Novkovic

Biljana Novkovic

PhD
Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

Click here to subscribe

RATE THIS ARTICLE

1 Star2 Stars3 Stars4 Stars5 Stars
(38 votes, average: 4.79 out of 5)
Loading...

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.