DAO Deficiency: How to Increase DAO Enzymes Quickly & Naturally

DAO deficiency histamine intolerance

Reduce histamine symptoms by increasing DAO enzymes

DAO deficiency histamine intolerance

If you suffer from histamine intolerance, the diamine oxidase (DAO) enzyme may be a key factor to focus on, as DAO deficiency is one of the most common causes underlying the disorder.

The DAO enzyme is the enzyme which is responsible for degrading histamine. So, if you possess a DAO deficiency, your ability to degrade histamine can be drastically hindered.

Let's look into exactly how a DAO deficiency may be connected with your histamine intolerance symptoms, what could be causing your DAO deficiency and, how to increase DAO enzyme levels naturally.

What is histamine intolerance?

Histamine Intolerance occurs due to the overproduction and accumulation of histamine in the body and the inability to break it down, resulting in a range of chronic symptoms similar to an allergic reaction (1).

Other symptoms associated with histamine intolerance include gastrointestinal disorders (irritable bowel syndrome), sneezing and nose congestion (2). urticaria (3), atopy, itch (pruritus), and asthma (4).

Although many of these histamine intolerance symptoms appear to mimic an allergic response, the good news is that histamine intolerance is not considered to be an allergic reaction, as it is not mediated by the same compounds as typical food allergies.

For this reason, histamine intolerance is not usually considered to be life threatening. However, the symptoms of histamine Intolerance can be quite severe and debilitating for some sufferers, drastically affecting daily quality of life. Unwanted symptoms can impact the enjoyment of eating out and social events, leading to a constant worry over what to eat.

Recent research shows that at least 1 percent of the world’s population suffers from histamine intolerance and, of those, almost 80% affected are middle-aged women (5).

Frustratingly, the existence of histamine intolerances is frequently misunderstood and underestimated by the medical profession. Although histamine intolerance can be diagnosed upon the presentation of two or more of the typical symptoms of histamine intolerance (6), understanding the root cause is vital for the appropriate management of symptoms (1).

So, how is the DAO enzyme related to this and how do you know if DAO deficiency is acting as a root cause in your histamine intolerance?

DAO Enzyme and DAO Deficiency

Research has shown that there are several different reasons for developing histamine intolerance (7). However, histamine intolerance primarily occurs due to an inability for the body to break histamine down at an appropriate rate.

This process requires two naturally occurring enzymes known as the DAO enzyme and histamine N-methyltransferase (HNMT). Due to either genetics or acquired reasons, the body might not be able to produce enough of these enzymes (1).

In fact, recent research has found that DAO deficiency accounts for over 70% of all histamine intolerance (8)!

The DAO enzyme is produced in the intestine, mainly in the intestinal mucosa and its function is essential to breaking down histamine in order to balance internal histamine levels (1).

Impaired functioning of the DAO enzyme or a DAO deficiency can therefore lead to an excessive build-up of histamine in the body associated with histamine intolerance (8).

Additionally, possessing a DAO deficiency can go on to affect multiple organs (lungs, skin, cardiovascular system, brain, digestion, etc.) leading to numerous symptoms. Depending on the severity of the DAO deficiency, these symptoms can occur even after the ingestion of a small amount of histamine (8).

Elevated histamine concentrations are also associated with an imbalance between the amount of histamine that is released from the cells in response to certain triggers, as well as a build-up of histamine in the body as a result of consuming certain foods such as high histamine foods (9-11).

Even if you're eating a seemingly healthy, all-natural diet, numerous foods may not only be high in histamine themselves but, may actually inhibit DAO (12,13), thus causing the histamine symptoms you experience.

It's important to note that histamine symptoms don’t always appear immediately and, they may appear when the body accumulates histamine throughout the course of the day. Therefore, an additional benefit of adopting a low histamine diet is that it serves as a further diagnostic tool to confirm the presence of histamine intolerance.

What Causes DAO Deficiency?

There are several factors that may reduce DAO activity or produce a DAO deficiency including:

  • Genetic inheritance - individuals may possess a genetic mutation which results in reduced production of the DAO enzyme, creating a DAO deficiency
  • Medications – both prescription and over-the-counter medications may contribute to reduced diamine oxidase enzyme levels
  • Hormonal imbalances - Imbalances in oestrogen and progesterone may contribute to a DAO deficiency
  • Gastrointestinal disorders - disorders such as irritable bowel syndrome, Crohn’s disease, ulcerative colitis, Celiac disease and small intestinal bacterial overgrowth SIBO) may all contribute to reduced functioning of the DAO enzyme or reduced DAO production resulting in a DAO deficiency
  • Nutrient deficiencies - nutrients including B6, vitamin C, zinc and copper, are required for the production of the DAO enzyme, therefore deficiencies in these nutrients may contribute to a DAO deficiency
  • Consuming histamine-rich food - some foods may inhibit the production or functioning of the DAO enzyme, or contribute to symptoms by overloading the body with more histamine than the DAO enzyme can break down 
  • Alcohol as a blocker or inhibitor of DAO - Alcohol is a potent inhibitor of the DAO enzyme, thus contributing to increased histamine symptoms, on top of being high in histamine itself

A vicious circle may occur if there is impaired DAO activity, resulting in increased plasma histamine concentrations (14) which in turn leads to unwanted symptoms, which have been shown to inhibit HNMT activity, the second enzyme required for metabolizing histamine (14). 

How to Increase DAO Enzymes Naturally

To date research has determined that there are many factors that negatively impact on the amount of DAO enzyme synthesized in the body (1,15). The good news, is that, acquired histamine intolerance may only be transient and potentially reversible.

1. Low histamine diet - encouraging results of a recent study have found that dietary modification is the first intervention to reduce symptoms associated with histamine intolerance (15), and allow the DAO enzyme to catch up to the amount of incoming histamine.

A study carried out in 2017 was able to establish that dietary modification could positively influence DAO enzyme transport and DAO enzyme bioavailability, ready for the body to utilize more efficiently. Furthermore, specific dietary modification were found to regulate the transportation of available DAO enzyme into the gut and bloodstream, thereby positively impacting on the degree and location of DAO enzyme activity (15).

If you don't feel like your diet is adequately reducing your histamine levels, enhancing your health and supporting your DAO levels, click the button below to download my free eBook which contains a full list of 102 high histamine foods to avoid, along with step-by-step guidance for reducing your symptoms and discovering the root cause of your intolerance.

2. Balancing fats - When it comes to dietary factors, some of the most interesting and relevant results for increasing DAO enzymes have been in relation to fat consumption.

Favourable results were achieved by the dietary modulation of fats, in particular increased intakes of the Omega-9 fatty acid - monounsaturated fats, a primary source of oleic acid (15).

Intakes of olive oil, in particular, were shown to substantially increase the release of the DAO enzyme into the blood stream by up to 500% (15)!

Other good sources of oleic acid include lard and nuts like macadamias.  Oleic acid has been shown to have many other health benefits, especially when consumed as part of a Mediterranean-style diet (16).

The pro-inflammatory Arachidonic Acid, a polyunsaturated omega-6 fatty acid, found in offal, fatty red meat, dairy, especially hard cheeses and eggs was found to cause the highest increase in histamine, when compared to other foods. In addition, increased intakes of linoleic acid, a polyunsaturated - omega- 6 fatty acid, as found in vegetable, nut and seed oils (including flaxseed and canola oil) also led to elevated histamine levels (15).

Reducing intake of Omega-6, as found in processed foods and vegetable oils, whilst increasing intakes of Omega-3 fatty acids (including fatty fish, seafood) has been shown to beneficially moderate inflammation in the body and help reduce the risk and symptoms of histamine intolerance (15).

As you can see, balancing fats effectively has achieved beneficial results regarding DAO enzyme activity.

Important factors in balancing fats include using heat stable oils, including ghee and pressed coconut oil for baking and cooking at high temperatures, regularly consuming oleic acid including olive oil and macadamia oil for light cooking, and avoiding industrial seed oils and sources of linoleic acid (15).

3. Protein intake - protein intake is responsible for the release of the DAO enzyme in the gut. Consuming a wide-range of grass-fed, organic protein and including protein sources from fresh seafood were found to lead to a beneficial increase of DAO activity (15).

In fact, good quality ingested protein may help to release the DAO enzyme from the intestinal mucosa into the gut, helping to deal with ingested amines and histamines, whilst preventing a build-up of histamine levels in the body.

4. Minimizing harmful ingredients  - another interesting factor to consider is that avoiding artificial ingredients and pesticides has been associated with increased DAO enzyme activity - so, eating as naturally as possible is always going to be a positive for your health and for increasing the DAO enzyme naturally!

5. Supporting gut health - as mentioned, the majority of the DAO enzyme is produced in the gut. Therefore, promoting your gut health and supporting your gut bacteria through the use of low histamine probiotics provides an important foundation for reducing histamine symptoms.

6. Taking specific nutrients - deficiency of the DAO cofactors, zinc, copper and vitamin B-6 and vitamin C, has also been associated with elevated histamine concentrations and reduced DAO activities. Therapeutic supplementation of these nutrients can increase DAO enzymes and offer further relief from the symptoms of histamine intolerance (17,18).

7. DAO supplementation -increased DAO enzyme levels in the body can also be achieved through DAO supplementation. Recent research has found that, irrespective of whether or not histamine was ingested, additional DAO supplementation led to a reduction in symptoms of histamine intolerance [19].

DAO supplementation has been found increase the release of DAO into the bloodstream, helping to actively degrade amines and histamine throughout the whole body (8)

A couple of issues with this is that you cannot find vegan sources of DAO, as they are typically isolated from a porcine kidney protein concentrate and, it's difficult to find DAO supplements in general.

Although I don't personally use a DAO supplement with my clients (I'll explain the method I use in the next section), you can find some decent brands on Amazon if you're interested.

I've done a bit of research for you, and the DAO supplement I would select can be found here

8. Reduce histamine release - this is the method I use with many of my clients via supplementation with Natural D-Hist. Although reducing histamine release doesn't directly increase the DAO enzyme, it does give your body a break from the inflammation and destruction in order to allow the DAO enzyme to catch up and calm your symptoms.

Additionally, by controlling the body's natural histamine release, my clients typically find they can tolerate much higher levels of dietary histamine before their body becomes overloaded and breaks out into symptoms.

This method means less dietary restrictions and less symptoms, so that you can eat a wider variety of foods and live a more normal daily life faster than other therapies allow for.

The natural supplement I use to reduce histamine release is called Natural D-Hist, and my clients have referenced it as their "miracle in a bottle" or their "wonder-drug."

Overall, this method gives your body a chance to fix the underlying issue naturally while providing it with the support it needs, so that the long-term impact can be to rebalance the underlying issue that was causing the DAO deficiency in the first place. 

Implementing Changes

Now that you have 8 ways to increase DAO naturally, it's time to get started.

The steps above are all simple and can be done in your own home - so, I encourage you to begin implementing them right away. Because, why wait?

If you haven't already read the low histamine diet eBook I've created, click on the button below to get my free eBook containing the web's most comprehensive high histamine foods list, additional methods for symptom relief and how to discover the root cause of your intolerance.

Life's too short to let symptoms control you.

Your histamine intolerance expert,

Anita Tee, Nutritional Scientist


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  2. Steinbrecher I, Jarisch R. Histamin und Kopfschmerz.(2005) (Histamine and headache.) Allergologie  28:84–91 (in German).
  3. Lessof MH, Gant V, Hinuma K, Murphy GM, Dowling RH (1990). Recurrent urticaria and reduced diamine oxidase activity. Clin Exp Allergy ;20:373–6.
  4. Wantke F, Hemmer W, Haglmuller T, Gotz M, Jarisch R.(1996). Histamine in wine. Bronchoconstriction after a double-blind placebo-controlled red wine provocation test. Int Arch Allergy Immunol, 110:397–400
  5. Missbichler A. Diagnostischer Nachweis der Aktivität von Diaminooxidase in Serum oder Plasma. (2004) (Diagnostic proof of the DAO activity in serum and plasma.) In: Jarisch R. ed. Histamin-Intoleranz. Histamin und Seekrankheit. (Histamine intolerance. Histamine and motion sickness.)  Stuttgart, Germany: Georg Thieme Verlag KG,:8–17 (in German).
  6. Jarisch R.(2004). Histamin-Intoleranz. (Histamine intolerance.) Aerztemagazin  8:1–4 (in German).
  7. Raithel M. Durchfälle und weicher Stuhl. In: Jarisch R. ed. Histamin-Intoleranz. Histamin und Seekrankheit (2015) (Histamine intolerance. Histamine and motion sickness.)  Stuttgart, Germany: Georg Thieme Verlag KG, 2004:77–110 (in German).
  8. Manzotti G, Breda D, Di Gioacchino M, Burastero SE, (2015) Serum diamine oxidase activity in patients with histamine intolerance, Int J Immunopathol Pharmacol. 2015 pii: 0394632015617170.
  9. Bodmer S, Imark C, Kneubuhl M.(1999). Biogenic amines in foods: histamine and food processing. Inflamm Res;48:296–300.
  10. Sarkadi L. Histamine in food. In: Falus A, Grosman N, Darvas Z.(2004). eds. Histamine: biology and medical aspects.  Budapest, Hungary: Spring Med Publishing, 176–85.
  11. Steinbrecher I, Jarisch R. Histamin und Kopfschmerz (2005). (Histamine and headache) Allergologie, 28:84–91 (in German).
  12. Nordic Council of Ministers Present status of biogenic amines in foods in Nordic countries. Tema Nord 2002: 524 (ISBN: 92-893-0773-0). Cited by: Sarkadi L. Histamine in food. In: Falus A, Grosman N, Darvas Z. (2004) eds. Histamine: biology and medical aspects.  Budapest, Hungary: SpringMed Publishing, 176–85.
  13. Wantke F, Hemmer W, Gotz M, Jarisch R. (1997). Adverse reactions to alcoholic beverages: a diagnostic guideline. Clin Exp Allergy ;27:343 (abstr).
  14. Ahrens F, Gabel G, Garz B, Aschenbach JR. (2002). Release and permeation of histamine are affected by diamine oxidase in the pig large intestine. Inflamm Res  51(suppl):S83–4.
  15. Wollin, A, wang, X, Tso, P. (2017) Nutrients regulate diamne oxidase release from intestinal mucosa). The American Physiological Society, 20, 220
  16. S. Terés, G. Barceló-Coblijn, M. Benet, R. Álvarez, R. Bressani, J. E. Halver and P. V. Escribá (2008). Oleic acid content is responsible for the reduction in blood pressure induced by olive oil.  PNAS 2008 September, 105 (37) 13811-13816
  17. Johnston CS. (1996). The antihistamine action of ascorbic acid. Subcell Biochem ;25:189–213.
  18. Enteroimmunology: A Guide to the Prevention and Treatment of Chronic Inflammatory Disease – Charles A Lewis
To improve gut health with a scientist on your side, get daily tips using:

Anita Tee, Msc

Anita Tee is a highly qualified and published nutritional scientist, carrying a Master of Science in Personalized Nutrition and a Bachelor of Science in Human Biology, specializing in Genetic & Molecular Biology.

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