For those struggling with histamine or mast cell mediated issues, managing symptoms can feel like a never-ending puzzle. One crucial piece of this puzzle is understanding Diamine Oxidase (DAO).
This enzyme plays a vital role in breaking down histamine in the body, and ensuring optimal quantity and function can significantly improve your quality of life.
What is DAO?
Diamine Oxidase (DAO) is an enzyme that primarily exists in the intestines and kidneys. Its primary function is to break down excess histamine, a compound involved in local immune responses, regulation of stomach acid, and that functions as a neurotransmitter impacting the brain.
Think of this enzyme as chemical scissors—they break apart histamine so it can be metabolized and cleared from your body.
When histamine levels become too high, it can lead to various symptoms such as headaches, hives, digestive issues, asthma, eczema, itching, and more. DAO helps to keep histamine levels in check, thus preventing these bothersome symptoms.
DAO's Role in Breaking Down Histamine
Histamine is present in many foods, can also be produced in your gut by certain gut microbes and is also released by mast cells during allergic reactions or mast cell activation.
Under normal conditions, DAO breaks down histamine from foods or microbes in the digestive tract before it enters the bloodstream. However, when DAO levels are low or its function is impaired, histamine accumulates, leading to symptoms. This accumulated histamine can also act as a trigger for mast cell activation.
DAO Helps with Symptom Management
By breaking down histamine, DAO helps to manage and alleviate symptoms associated with histamine intolerance and MCAS.
Supporting DAO production and activity can help reduce the frequency and severity of reactions such as:
Migraines and headaches
Skin issues like hives, itching, and eczema
Digestive problems including bloating, diarrhea, and abdominal pain
Respiratory issues such as nasal congestion and asthma
Fatigue, sleep problems, poor concentration, and brain fog
Pain anywhere in the body including joints, muscles, bone, bladder, heart...
Urinary issues, PMS and reproductive issues
DAO Production
Gut Health: A healthy gut is crucial to produce DAO. The enzyme is produced by the cells lining the small intestine, so maintaining a healthy gut lining is essential. Inflammation, gut infections, or leaky gut can impair DAO production.
Genetics: Genetic variations in the AOC1 gene can affect DAO levels. Some people have a variation of this gene that results in lower DAO production making them more susceptible to having higher histamine levels.
Get DAO From Foods
Certain foods naturally contain DAO and can help increase its levels in your body, but some of these foods also have the potential to trigger histamine release from mast cells.
Here’s what you need to know about food sources of DAO:
Pea shoots: these are our favourite food source of DAO. They have a fresh, subtle pea flavour, and are great additions to salads or on top of a bowl of soup or stew. You can find these at most health food stores and farmers’ markets. Add them to your shopping list! (And use only the sprout above the seed.)
Pork kidney: kidney is a great source of DAO, plus it is high in some of the nutrients needed to support DAO production, but it’s also high in histamine. As you move through a process of self-discovery (Histamine Haven is here to help you with that process), you may find you can introduce this food. Offal doesn’t appeal to everyone, so if you don’t like the idea of eating kidney, stick with pea shoots.
Kidney beans: legumes contain DAO with kidney beans being at the top of the list. Kidney beans can trigger a histamine release from mast cells, so we don’t recommend this food. Legumes are high in lectins which can contribute to leaky gut, reducing your gut’s ability to make DAO. Just because a food is high in DAO, doesn’t mean you should eat it. We’re here to make sure your get all the information you need to make informed decisions.
Nutrients Needed to Support DAO Production
Several nutrients are essential for the optimal production and activity of DAO (it means when you have adequate amounts of these nutrients in your diet, now you'll better be able to make the DAO enzyme yourself):
Vitamin B6: B6 is found in abundantly in animal foods like salmon, poultry and pork. Pistachios and sweet potatoes are also good sources.
Copper: Choosing low histamine sources of copper can be tricky. Liver and shellfish are excellent sources but are high in histamine. Nuts like almonds, Brazil nuts, or pistachios are good choices. Pumpkin seeds, or hemp seeds are also good choices. Nuts and seeds should be soaked and activated to make the copper bioavailable. (We outline this process in our cookbook.) Swiss chard is a leafy green that boasts good amount of copper as well. You’ll be able to absorb more copper if you eat it cooked.
Zinc: Just like copper, the best sources of zinc like shellfish and beef are high in histamine. Instead choose chicken or pork. Soaked and activated pumpkin seeds are another option to get zinc.
Vitamin C: Most foods that come to mind when you think of vitamin C are high in histamine or trigger the release of histamine. Low histamine vitamin C options include fruits like blackberries, cherries, cranberries, cantaloupe and pomegranate. Vegetable sources include asparagus, broccoli, Brussels sprouts, and cabbage. Parsley is rich in vitamin C so chop this herb and use it liberally in your meal preparation.
Eat abundantly from these foods to ensure you have and adequate intake of all the nutrients needed to optimize DAO production. Need a convenient food list to follow? Download a list here.
Addressing Nutrient Deficiencies
If you are deficient in any of these nutrients, your body may struggle to produce adequate levels of DAO. Ensuring you have a sufficient intake of these foods is essential for supporting DAO production and managing histamine levels effectively.
The recipes in Histamine Haven are all designed with nutrient density in mind. Get the book here.
Supporting Gut Health for Optimal DAO Production
To ensure your gut can produce adequate amounts of DAO, focus on maintaining overall gut health. Here are some strategies:
Eat Animal Protein: Protein helps release DAO in the gut (1) and animal sources are rich in glycine to help restore a healthy gut barrier where DAO gets produced.
Avoid High-Histamine Foods:These can include aged cheeses, fermented foods, alcohol, and certain processed meats. The high histamine content of these foods can trigger a mast cell response in the gut lining resulting in increased inflammation and GI symptoms.
Avoid DAO Blocking Foods: Additionally, some foods and beverages like alcohol, black tea, green tea, maté, energy drinks, food additives and raw egg whites can block DAO activity. When DAO is blocked it can’t perform its function of breaking down histamine in the gut.
Manage Stress: Chronic stress can negatively affect gut health. Practices like meditation, yoga, and deep breathing can help improve gut health.
Limit Use of NSAIDs and Antibiotics: These can damage the gut lining and disrupt the balance of gut bacteria. The damage in the gut lining means reduced DAO production.
Be Aware of Medications: Some medications can decrease DAO or inhibit it (2). Consult with your medical doctor or pharmacist to understand how your medications might be affecting your DAO levels.
Food For Thought
DAO is continually being made in the gut and absorbed into the lymphatic system. This is the same pathway that long chain fatty acids use to be absorbed, and eventually make their way into the bloodstream.
Animal studies support that long chain fatty acids such as safflower and soybean oil induce mast cell degranulation with histamine, prostaglandin D2, and interleukin-6 release in the lymphatic tissue (3). Histamine relaxes lymph vessels slowing down the flow (4), which is not a desirable result for immune health.
Other research shows that safflower oil and soy bean oil increase diamine oxidase in the intestinal lymph (5).
These oils have a high omega 6 content, making them inflammatory fats.
Is it possible that the high DAO levels found in lymph are the body’s response to cope with the inflammatory mast cell mediators that are released when these oils are consumed and enter lymph?
We can’t find the answer to that question, but think it is worth considering.
Olive oil and food high in oleic acid have been found to increase DAO in the lymph by 500%. (6). Is this healthy fat also inducing the same mast cell response as safflower and soybean oils?
Again, we don’t have an answer to this question, but we speculate that based on all the research available on olive oil, that it would not trigger this response in the lymph.
So how does this translate to actionable steps for those of us who may be struggling to make adequate amounts of DAO? The invitation is now to consume olive oil, lamb and other meats, eggs, avocado oil and low histamine nuts like pecans, macadamia nuts or almonds to get healthy sources of oleic acid into your diet, and in turn, help support the body to make more DAO.
Everyone with MCAS has unique food triggers. Always listen to your own body before relying on what the research says (or in this case, doesn’t say).
The Role of DAO Supplements
For individuals struggling to manage histamine intolerance or MCAS through diet alone, DAO supplements can be a valuable tool. These supplements, available in both plant and animal-based forms, can help to increase DAO levels in the body and support the breakdown of histamine.
Disclaimer: We have no affiliations with these companies. We're simply sharing those we've personally tried or seen success with through our clients. Have one to add to the list? Send us a message.
Recommended DAO Supplements in North America:
Histamine Digest by Seeking Health: This supplement contains porcine kidney extract, a natural source of DAO.
HistDAO by Xymogen: A well-regarded product that is currently being reformulated and is expected to reappear in the summer of 2025.
Histamine Digest by Omne Diem: Contains DAO enzyme to support digestive health and manage histamine levels.
Availability of supplements varies from country to country. Find a product that is available locally and that works for you. (At the time of publication of this blog post, it is very hard to find a Canadian source for any of these supplements.)
When choosing a DAO supplement, especially for those with mast cell activation, it is crucial to select a high-quality product free of additives, common allergens, and artificial ingredients. Individuals with MCAS may react to fillers and additional ingredients in supplements, so opting for a pure, clean supplement is essential for managing symptoms effectively.
How Supplements Can Aid Symptom Management
Taking DAO supplements about 15 minutes before meals can be particularly helpful, especially in situations where you cannot control or know the histamine content of your food, such as dining out or attending social gatherings.
If you forget to take it in advance, taking it right before a meal is still beneficial. By boosting your DAO levels before eating, you can help to mitigate the potential histamine overload and reduce the risk of triggering symptoms.
Adjusting Your Supplement Dosage
It's important to note that some individuals may need more DAO than others. If the amount listed on the supplement bottle isn't producing the desired effects, it is advisable to discuss alternate dosing with a healthcare practitioner or reach out to the company that produces the supplement.
They can help you slowly build up the dose to find the right amount for your needs, ensuring that you manage your symptoms effectively without overdoing it. If you tend to be sensitive to supplements, consider opening a capsule and starting with a very small amount, gradually building up the dose.
Testing for DAO Levels and Gut Health
Testing can be a powerful tool to understand what's happening with your DAO levels and overall gut health.
Here are some key areas where testing can help:
DAO Level Testing: Specific tests can measure the amount of DAO in your blood, giving you a clearer picture of your enzyme levels and helping to guide your management strategy.
Gut Health Testing: Comprehensive gut tests can identify dysbiosis (an imbalance in gut bacteria), leaky gut, infections, and gut inflammation. These factors can significantly reduce DAO production. If you have leaky gut, you also won't absorb the nutrients needed to make DAO effectively.
Food Sensitivity Testing: Identifying food sensitivities can help you pinpoint which foods contribute to gut inflammation, allowing you to adjust your diet to support better gut health and DAO production.
Genetic Testing: Genetic testing can reveal variations in the AOC1 gene (also known as ABP1) that impact DAO production. Knowing your genetic predisposition can help tailor your approach to managing your symptoms.
DAO For Symptom Management
Understanding and supporting DAO production is crucial for managing histamine and mast cell mediated symptoms. By focusing on gut health, consuming nutrients that support DAO, including natural sources of DAO in your diet, using supplements strategically, and utilizing appropriate testing, you can help manage your symptoms and improve your overall well-being.
Additionally, taking these steps can help reduce your symptoms and allow you to reintroduce foods with higher histamine content. However, while DAO is a great support, it will not fix a histamine or mast cell problem on its own.
Addressing root contributors is essential and should be done as part of a holistic health model to achieve optimal wellness.
Find this kind of information daunting? Unsure as to how to move forward in finding relief for yourself?
We have two potential next steps for you.
Step 1 - Get our book.
We walk you through a lot of this type of information, and share the science behind it all. We also provide lots of resources & recipes to help you know how to feature these foods in your regimen without the worry of tripping more symptoms.
Get more information on the book here, or order online by name at your favourite online retailer.
Step 2 - Get started on solutions.
Start with our free Master Class webinar we call The Histamine Connection. We always run one every month or so - it's at this class that we get you started on understanding what's going on and get you going on solutions. Find out when the next class is happening and register for it here.
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