Advanced Intestinal Barrier Test

(Leaky Gut Test)

What's The Purpose Of The Advanced Intestinal Barrier Test?

The health of the gut and gut wall plays a role in over 80% of the immune system and has a direct connection with the brain through the vagus nerve. The integrity of the gut wall can be linked to many digestive tract disorders as well as auto-immune conditions and psychological and behavioral issues.  When the integrity of the gut lining or gut wall gets damaged this is more commonly referred to as Leaky Gut.  To understand more about Leaky Gut and how it impacts your health check out this blog post titled Leaky Gut: Explained In Plain English.

Helping to identify and restore health to the gut lining is critical to the health of the body.

This advanced assessment of the intestinal barrier enables an understanding of the integrity of the barrier, and helps to understand why.

The biomarkers include zonulin, which regulates tight junctions. Diamine oxidase (DAO), which is produced in the microvilli; a deficiency may indicate microvilli atrophy. Certain drugs, foods and bacteria may also suppress its production. DAO breaks down histamine, which is a compound that affects the immune response, physiological function of the digestive tract, and acts as a neurotransmitter. LPS is a bacterial endotoxin. Increased levels are indicative of intestinal permeability via transcellular and paracellular pathways. When LPS is absorbed into systemic circulation it can elicit a strong immune response.

Testing histamine along with diamine oxidase (DAO) levels provides important information that standard food sensitivity tests may not reveal, and may be the real culprit when food sensitivities are suspected.

Summary of the Biomarkers

The Advanced Intestinal Barrier Test measures 3 main biomarkers: DAO, histamine, the DAO: Histamine ratio, and Zonulin.

  • Diamine oxidase is an enzyme that breaks down histamine.

  • Histamine is a compound that affects immune response, physiological function of the digestive tract, and acts as a neurotransmitter.

  • Zonulin is a eukaryotic protein structurally similar to Vibrio cholerae's zonula occludens toxin. It plays an important role in the opening of small intestine tight junctions.

Why Test Diamine Oxidase (DAO)?

Diamine oxidase is the body’s primary enzyme for breaking down ingested histamine and a natural defense against histamine excess. If you ingest too much dietary histamine or produce more than your DAO level can handle, reactions can occur. DAO is produced in the small intestine but certain drugs, foods, and bacteria may suppress its production.


Low DAO levels are associated with the following symptoms and conditions:

  • Migraine, headache

  • Chronic fatigue

  • Hives, skin rash, eczema, psoriasis

  • Nasal congestion, asthma

  • Gastrointestinal disorders, inflammation, irritable bowel syndrome

  • Dysmenorrhea, PMS, estrogen dominance

  • Arrhythmia, hypertension, hypotension

  • Fibromyalgia, muscular pain

  • Rheumatoid arthritis

  • Neurological conditions such as multiple sclerosis and attention deficit and hyperactivity disorder (in childhood and adolescence)

  • Depression and anxiety


Symptoms of low DAO are similar to those of histamine excess since it is the DAO that breaks down and metabolizes the histamine. Patients suffering from urticaria (hives), Crohn’s or celiac disease show low DAO activity in serum or plasma.(1,2)


People with the inability to break down histamine react to many substances and will often improve on antihistamines. Since DAO is made in the gastrointestinal tract, low levels are also indicative of poor digestive function and a compromised intestinal barrier.


  1. Schmidt WU, Sattler J, Hesterberg R, et al. Human intestinal diamine oxidase (DAO) activity in Crohn's disease: a new marker for disease assessment? Agents and actions. Apr 1990;30(1-2):267-270.

  2. Corazza GR, Falasca A, Strocchi A, Rossi CA, Gasbarrini G. Decreased plasma postheparin diamine oxidase levels in celiac disease. Digestive diseases and sciences. Aug 1988;33(8):956-961.

  3. Maintz L, Novak N. Histamine and histamine intolerance. Am J Clin Nutr. May 2007;85(5):1185-1196.

  4. Banks WA, Robinson SM. Minimal penetration of lipopolysaccharide across the murine blood-brain barrier. Brain, behavior, and immunity. Jan 2010;24(1):102-109.

  5. Yue G, Shi G, Azaro MA, et al. Lipopolysaccharide (LPS) potentiates hydrogen peroxide toxicity in T98G astrocytoma cells by suppression of anti-oxidative and growth factor gene expression. BMC genomics. 2008;9:608.

Sample Test Report Details

Total Cost: $499

(This test requires a blood draw at Labcorp with no additional fee)