What Is Leaky Gut Syndrome (Intestinal Permeability)?

A Theory That Toxins Pass Through the Gut and Trigger Symptoms

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Leaky gut syndrome (or intestinal permeability) is a condition that affects the lining of the intestines. This can result in symptoms like persistent muscle or joint pain, poor concentration, indigestion, gas, mood swings, nervousness, skin rashes, recurrent bladder or yeast infections, constipation, or anxiety.

However, there is no scientific data in humans that a leaky gut resulting in increased intestinal permeability causes symptoms outside the gastrointestinal (GI) tract. Leaky gut syndrome is considered a theory, rather than a condition traditionally recognized by the general medical community.

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Symptoms of Leaky Gut Syndrome

Symptoms of leaky gut include:

  • Abdominal pain
  • Asthma
  • Chronic joint pain
  • Chronic muscle pain
  • Confusion
  • Gas
  • Indigestion
  • Mood swings
  • Nervousness
  • Frequent colds
  • Recurrent vaginal infections
  • Skin rashes
  • Diarrhea
  • Recurrent bladder infections
  • Poor memory
  • Shortness of breath
  • Constipation
  • Bloating
  • Anxiety
  • Irritability
  • Fatigue


Potential causes of leaky gut syndrome include:

  • Chronic stress
  • Intestinal infections
  • Small intestine bacterial overgrowth
  • Environmental contaminants
  • Excess alcohol
  • Poor diet
  • Nonsteroidal anti-inflammatory drugs (NSAIDs) and other medications

Alternative practitioners sometimes associate leaky gut syndrome with the following conditions:

  • Autoimmune disease
  • Celiac disease
  • Crohn's disease
  • Environmental illness
  • Hives
  • Acne
  • Allergies
  • Inflammatory joint disease/arthritis
  • Intestinal infections
  • Pancreatic insufficiency
  • Ulcerative colitis
  • Giardia (a parasitic intestinal infection)
  • Chronic fatigue syndrome
  • Eczema
  • Psoriasis
  • Food allergies and sensitivities
  • Liver dysfunction
  • Rheumatoid arthritis
  • Irritable bowel syndrome

The lining of the intestines creates a barrier that normally allows only properly digested fats, proteins, and starches to pass through and enter the bloodstream. It allows substances to pass in several ways.

Chloride, potassium, magnesium, sodium, and free fatty acids diffuse through intestinal cells. Amino acids, fatty acids, glucose, minerals, and vitamins also cross through cells, but they do it by another mechanism called active transport.

There's a third way that substances can pass through. The spaces in between the cells that line the intestines are typically sealed. These tight junctions are called desmosomes. When the intestinal lining becomes irritated, the junctions loosen and allow unwanted larger molecules in the intestines to pass through into the blood. The immune system sees these unwanted substances as foreign (because they aren't usually present in the blood). This triggers an antibody reaction.

When the intestinal lining becomes further damaged, even larger substances, such as disease-causing bacteria, undigested food particles, and toxins, pass directly through the damaged cells. Again, the immune system is alerted, and antibodies and substances called cytokines are released. Cytokines alert white blood cells to fight the particles. This fight produces oxidants, which cause irritation and inflammation throughout the body.


The standard test for leaky gut syndrome is the mannitol and lactulose test. Both are water-soluble molecules that the body can't use. Mannitol is easily absorbed by people with healthy intestinal linings. Lactulose is a larger molecule and is only slightly absorbed.

For the test, a person drinks a mannitol and lactulose solution. Urine is collected for six hours, and the amount in urine reflects how much of each was absorbed by the body.

A healthy test shows high levels of mannitol and low levels of lactulose. If high levels of both molecules are found, it indicates a leaky gut condition. If low levels of both molecules are found, it indicates general malabsorption of all nutrients.

A Word From Verywell

It's important to keep in mind that there is limited research about leaky gut syndrome. It's also important to note that self-treating a condition and avoiding or delaying standard care may have serious consequences. If you're experiencing any symptoms or are concerned about your health, consult your physician.

Frequently Asked Questions

  • Is leaky gut a recognized medical condition?

    No, leaky gut is not a recognized medical diagnosis, but it is used in alternative health circles. According to the concept of leaky gut, intestinal permeability causes various health symptoms. While the intestinal lining can be dysfunctional, there is no evidence that this can contribute to illness. 

  • What are the symptoms of leaky gut syndrome?

    According to alternative medicine practitioners, leaky gut can cause abdominal pain, asthma, bloating, chronic joint pain, chronic muscle pain, confusion, constipation, diarrhea, frequent colds, irritability, gas, indigestion, memory problems, mood swings, nervousness, recurrent vaginal infections, shortness of breath, and skin rashes.

  • How is leaky gut treated?

    Leaky gut is treated with diet and supplements. Recommended dietary approaches to treating leaky gut include eating more fruits and vegetables and avoiding certain foods. If you have leaky gut syndrome, you may need to avoid beans, legumes, corn, cruciferous vegetables, bran, fried foods, full-fat dairy, chocolate, pastries, cookies, xylitol, sorbitol, brown rice, soda, caffeine, and alcohol. 

  • What supplements can help leaky gut syndrome?

    Probiotic supplements are often recommended by alternative health professionals to treat leaky gut syndrome. Probiotics are often used to help balance intestinal bacteria and promote gut health.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Solan M. Putting a stop to leaky gut. Harvard Health Publishing. 2018.

  2. Camilleri M. Leaky gut: mechanisms, measurement and clinical implications in humans. Gut. 2019;68(8):1516-1526. doi:10.1136/gutjnl-2019-318427

  3. Bishehsari F, Magno E, Swanson G, et al. Alcohol and Gut-Derived InflammationAlcohol Res. 2017;38(2):163-171.

  4. Harvard Health Publishing. Putting a stop to leaky gut. 2018.

  5. Michielan A, D'Incà R. Intestinal Permeability in Inflammatory Bowel Disease: Pathogenesis, Clinical Evaluation, and Therapy of Leaky GutMediators Inflamm. 2015;2015:628157. doi:10.1155/2015/628157

  6. Bischoff SC, Barbara G, Buurman W, et al. Intestinal permeability--a new target for disease prevention and therapyBMC Gastroenterol. 2014;14:189. doi:10.1186/s12876-014-0189-7

  7. Sequeira IR, Lentle RG, Kruger MC, Hurst RD. Standardising the lactulose mannitol test of gut permeability to minimise error and promote comparabilityPLoS One. 2014;9(6):e99256. doi:10.1371/journal.pone.0099256

Additional Reading
  • Lipski E. Digestive Wellness. Keats Publishing/McGraw Hill, 2001.

By Cathy Wong
Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.