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DAO Enzyme Intestinal Integrity

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gut health

Restoring Gut Health for Optimal Wellness with DAO Enzyme Intestinal Integrity

DAO Enzyme and Intestinal Integrity

Diamine oxidase (DAO) is an enzyme that helps in the metabolism of histamine, a biogenic amine found in some foods and produced by the body. DAO is considered the main enzyme responsible for gastrointestinal degradation of histamine.

Histamine intolerance is a clinical condition that can appear due to a DAO activity deficit, which can be treated with a low-histamine diet and oral DAO supplementation to enhance intestinal histamine degradation.

DAO is an enzyme synthesized by apical enterocytes located in the intestinal villi and is released from the mucosa for digestion and into the blood circulation. It is also produced in many parts of the body, including the kidneys, thymus, and the intestinal lining of the digestive tract. 

Its primary function is to break down excess histamine in the body. DAO is not a digestive enzyme; it is responsible for the metabolism of histamine ingested from food.

Role of DAO in Regulating Intestinal Mucosa

The activity of DAO is highest in rapidly proliferating tissues such as the bone marrow and intestinal mucosa, and DAO is a regulating enzyme in these tissues. DAO is found in the apical villous cells of the small intestine mucosa. 

Its function is the oxidative deaminating of several polyamines, essential substances for cell proliferation. DAO is thus a regulating enzyme in rapidly proliferating tissues such as bone marrow and intestinal mucosa.

DAO Activity and Its Correlation with Intestinal Maturity and Permeability

DAO activity is positively correlated with the maturity and integrity of the intestinal mucosa. Basal plasma levels of DAO are normally present in very small amounts in the circulation and are positively correlated with the maturity and integrity of the intestinal mucosa. DAO activity should reflect the status of the intestinal mucosa. 

When the intestinal barrier is compromised, DAO is released from the intestinal epithelium into the bloodstream, making serum DAO a marker for intestinal permeability. Measuring basal as well as post-heparin DAO levels has potential relevance following small bowel transplantation.

DAO and Intestinal Health in Crohn’s Disease Patients

Intestinal DAO activity is diminished in patients with Crohn’s ileitis and correlates with the severity of histologic changes. Tissue DAO activity might prove useful in predicting the risk of recurrence or anastomotic complications after resection for Crohn’s disease

DAO supplements can be taken to help break down excess histamine in the body and alleviate symptoms of histamine intolerance, but their efficacy may depend on the underlying cause of histamine intolerance.

Gut Morphology and Its Importance for Intestinal Function

Maintaining appropriate intestinal function depends on the integrity of the morphological structure of the intestine. The villus height (VH), crypt depth (CD), and the VH:CD ratio can provide information about gut health by assessing gut morphology. 

A shortening of the intestinal villus or an increase in crypt depth can decrease the surface area for nutrient absorption and reduce the capacity of the intestine to absorb nutrients. CEO (cinnamon essential oil) supplementation enhanced VH, CD, and the VH:CD ratio in nursery pigs, indicating an improvement in gut health.

Other Markers for Assessing Intestinal Health and Permeability

In addition to DAO, other markers can be used to assess intestinal health and permeability. Serum concentrations of D-lactic acid (D-LA) can reflect the degree of damage to the intestinal mucosa and intestinal permeability, and are positively correlated with serum DAO activity

Tight junction proteins such as claudins and occludins are also important indicators for evaluating the integrity of the intestinal barrier, as they regulate paracellular permeability.

How Low Diamine Oxidase From Leaky Gut Can Lead To Histamine Intolerance And Gut Healing Strategies

a woman eating fish and vegetable salad

Leaky gut refers to increased intestinal permeability where particles can ‘leak’ through the gut wall. Here are some key points regarding diamine oxidase and leaky gut:

Low levels of diamine oxidase have been linked to leaky gut and certain conditions like histamine intolerance, IBS, and inflammation. When the gut is “leaky”, it can allow undigested proteins and particles into the bloodstream, which can trigger immune reactions and inflammation.

Leaky gut may lead to lower levels of diamine oxidase because the enzyme can be damaged or depleted as part of the inflammatory response. Less diamine oxidase means less breakdown of histamine and amino acids, potentially exacerbating symptoms.

Increasing diamine oxidase levels through dietary changes or supplementation has been proposed as a potential strategy to help repair leaky gut and reduce histamine intolerance symptoms. Foods high in diamine oxidase include legumes, Lentils, asparagus, and fermented foods.

Other methods to potentially repair leaky gut and resolve issues of low diamine oxidase include gut healing supplements, a low FODMAP or elimination diet, and probiotics to improve gut barrier function and digestive health.


DAO is an important enzyme that helps in the metabolism of histamine, and its deficiency can lead to histamine intolerance. DAO supplements and a low-histamine diet are two approaches to managing histamine intolerance. While DAO supplements may help some symptoms, they may not be safe to take if you don’t have the condition. 

A low-histamine diet can improve histamine intolerance, and more than 50% of people have reported reduced symptoms. However, some studies found that a low-histamine diet didn’t change the enzyme activity in the body.

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