What Is the Function of DAO Enzyme in Human Health?

Educational content only. This article is for general informational purposes and is not medical advice. It is not intended to diagnose, treat, cure, or prevent any disease. Please consult a qualified healthcare professional before starting any dietary supplement or making changes to your diet, especially if you are pregnant, nursing, taking medication, or have a medical condition.

As awareness of digestive wellness and food sensitivities continues to grow, more consumers are learning about the important role DAO enzyme plays in the body. DAO, short for diamine oxidase, is a naturally occurring enzyme involved in the breakdown of histamine from foods and beverages.

For individuals interested in supporting digestive comfort and healthy histamine metabolism, understanding the function of DAO enzyme can be an important part of maintaining overall wellness.

In this article, we’ll explore what DAO enzyme is, how it functions in the body, why histamine balance matters, and how DAO supplementation may support a healthy lifestyle.*

Want the basic definition first? Start with our primer, What Is Diamine Oxidase (DAO) Enzyme?

What Does DAO Enzyme Do?

DAO has one main job. It breaks down histamine that comes from outside the body, mostly from food and drink.

Picture a kitchen sink. Histamine from your meals is the water coming in from the faucet. DAO is the drain. When the drain keeps up, the sink stays comfortably empty. When more water comes in than the drain can clear, the level rises. We explore this idea further in The Histamine Bucket.

In practical terms, DAO:

• Is released from intestinal cells into the digestive tract, where food histamine arrives
• Breaks histamine down into inactive compounds the body can clear
• Acts as a first line of processing for dietary histamine

DAO vs. HNMT: Your Body's Two Histamine Enzymes

Your body uses two main enzymes to process histamine, and they work in different places.

	DAO (diamine oxidase)	HNMT (histamine N-methyltransferase)
Where it works	Outside cells, mainly in the gut	Inside cells, throughout the body
Main source of histamine it handles	Food and drink	Histamine the body makes itself
Available as a supplement?	Yes	No

That's why DAO gets most of the attention in conversations about food and histamine: it is the enzyme positioned right where dietary histamine shows up.

Where Is DAO Produced in the Body?

The highest levels of DAO are found in the lining of the small intestine and colon. DAO is also present in the kidneys and, during pregnancy, the placenta, which produces large amounts of it.

Because most DAO activity happens in the gut, the health of the intestinal lining is closely tied to how well your body handles dietary histamine.

Why Histamine Balance Matters

Histamine is not the enemy. Your body depends on it for:

• Immune system signaling
• Stomach acid production and digestion
• Communication between nerve cells, including the sleep-wake cycle
• Normal, healthy inflammatory responses

The goal is balance, not elimination. Trouble tends to start when the amount coming in outpaces the body's ability to clear it.

Foods Higher in Histamine

Histamine builds up as foods age, ferment, or sit. Common higher-histamine foods include:

• Aged cheeses such as parmesan and aged cheddar
• Fermented foods such as sauerkraut, kimchi, and soy sauce
• Cured and processed meats
• Wine, beer, and other alcoholic drinks
• Vinegar and vinegar-based foods
• Certain fish and seafood, especially if not very fresh
• Tomatoes, spinach, and eggplant
• Leftovers stored for more than a day

See the full list in Foods High in Histamine. Some foods, like citrus and strawberries, are low in histamine but may prompt the body to release its own; learn more in What Are Histamine Liberators?

What Can Affect DAO Activity?

DAO levels differ from person to person, and several factors may influence how well the enzyme keeps up:

• Alcohol. Alcohol may interfere with DAO activity while also adding histamine, a double load. Read What Alcohol Is Highest in Histamine?
• Certain medications. Some common medications may reduce DAO activity. Ask your pharmacist or healthcare provider if this applies to you.
• Gut lining health. Since DAO is made in intestinal cells, anything that stresses the gut lining may affect output.
• Genetics. Natural variations in the gene that codes for DAO may influence how much enzyme a person makes.
• Nutrient status. DAO is a copper-dependent enzyme, so overall nutrition plays a role.
• Hormonal shifts. Hormone changes, including during pregnancy and perimenopause, are linked to changes in DAO and histamine levels.

What Are DAO Supplements?

A DAO supplement provides diamine oxidase enzyme in capsule form. It is taken shortly before a meal so the enzyme is present in the digestive tract when food histamine arrives. In sink-and-drain terms, it widens the drain for that meal.*

DAO supplements are not all the same. Two details matter most:

• Source. Most DAO supplements use either porcine (pork kidney) DAO or plant-based pea sprout DAO. Porcine DAO is the form used in the published human research to date. Compare the two in Pea vs. Porcine DAO.
• Potency. DAO activity is measured in HDU (histamine degrading units). A clearly stated HDU number per capsule tells you what you are actually getting.

The research on DAO supplementation is promising but still early, made up mostly of small human studies. We think it is worth being upfront about that.

When Do People Take DAO?

DAO supplements are taken shortly before eating, and many people reserve them for meals that are likely to be higher in histamine, such as:

• Restaurant meals and dining out
• Travel, when food choices are harder to control
• Holidays, parties, and social events
• Meals with aged cheese, cured meats, or fermented foods
• Occasions involving wine or beer

Always follow the directions on your product label.

What to Look for in a DAO Supplement

• A named, standardized DAO ingredient rather than an unspecified “enzyme blend”
• Stated HDU per capsule so you can compare products accurately
• Enzyme source disclosed (porcine or pea)
• Simple formulation without unnecessary fillers
• Manufacturing in a GMP-certified facility
• Clear allergen information

OmneDiem Histamine Digest

Everyday Habits That Support Healthy Histamine Balance

• Eat fresh. Cook and freeze rather than refrigerating leftovers for days.
• Notice patterns. A simple food journal can show which meals feel heavier for you.
• Pace alcohol. Choose lower-histamine options and space drinks out.
• Prioritize sleep and stress management. Both are tied to how the body handles histamine.
• Explore a low-histamine approach. Our low-histamine diet guide is a good place to start.

The Bottom Line

DAO is your body's built-in drain for dietary histamine. When it keeps up, histamine-rich meals pass without much notice. Diet, alcohol, medications, gut health, genetics, and hormones can all influence how well it works. For meals that put extra demand on your system, a DAO supplement like Histamine Digest may offer added support for healthy histamine metabolism.*

Related Resources

• DAO: The Enzyme at the Center of the Dietary Histamine Conversation
• What Is Diamine Oxidase (DAO) Enzyme?
• Pea vs. Porcine DAO
• Common Questions About DAO Enzyme