Diamine oxidase (DAO) is a digestive enzyme produced primarily in the kidneys, thymus, and the intestinal lining. Its main job is to break down histamine that comes from the food you eat.
If you think of histamine as a chemical messenger that can cause “allergic-like” symptoms when levels get too high, DAO is the cleanup crew that keeps those levels in check within the digestive tract.
How It Works
When you eat foods high in histamine (like aged cheeses, red wine, or sauerkraut), DAO goes to work in the small intestine. It neutralizes the histamine before it can pass into your bloodstream.
If DAO levels are sufficient, you likely won’t feel any effects from these foods. However, if DAO levels are low, histamine can build up, leading to a condition known as histamine intolerance.
Symptoms of Low DAO
When DAO isn’t doing its job, the resulting histamine buildup can cause a wide range of symptoms that often mimic an allergic reaction:
- Digestive: Bloating, abdominal pain, or diarrhea.
- Skin: Flushing, hives, or itching.
- Neurological: Migraines or headaches.
- Respiratory: Nasal congestion or sneezing.
What Causes Low DAO Levels?
Several factors can interfere with how much DAO your body produces or how well it functions:
- Gastrointestinal Issues: Since DAO is made in the gut lining, conditions like Crohn’s disease, Celiac disease, or SIBO can damage the cells that produce it.
- Genetics: Some people are genetically predisposed to produce less DAO.
- Medications: Certain drugs (like some antibiotics, heart medications, or antidepressants) can temporarily “block” DAO activity.
- Alcohol: Alcohol is a known DAO inhibitor, which is why some people experience immediate flushing or headaches when drinking.
Management
For those with a deficiency, management usually involves a low-histamine diet to reduce the “load” on the enzyme. Additionally, over-the-counter DAO supplements (usually derived from porcine kidney) can be taken before meals to help process histamine-rich foods.
What we Haven’t Touched about DAO! DAO needs Cofactors to work at top efficiency!
While the basics give a good starting point, there are several “advanced” aspects of DAO that are crucial for a full picture, especially if you’re looking into specific brands or managing symptoms more precisely.
Here is what we haven’t touched on yet:
1. The “Support Crew” (Cofactors)
DAO doesn’t work in a vacuum; it is a metalloprotein, meaning it requires specific minerals and vitamins to function. If you are deficient in these, your body might produce enough DAO, but the enzyme will be “turned off”:
- Copper: This is the central atom of the DAO enzyme. Without it, the enzyme can’t catalyze the breakdown of histamine.
- Vitamin B6: Specifically in its active form (P5P), B6 is a primary cofactor that enables the enzymatic reaction.
- Vitamin C: Acts as a stabilizer for the enzyme and helps lower histamine levels directly.
2. The Pregnancy “Superpower”
One of the most fascinating things about DAO is that during pregnancy, its production can increase by 500 to 1,000 times.
The placenta produces massive amounts of DAO to prevent maternal histamine from reaching the fetus (where it could cause premature contractions). This is often why women with chronic migraines or histamine issues suddenly feel “cured” while pregnant.
3. DAO vs. HNMT (The Other Enzyme)
DAO is only half the story. It handles extracellular histamine (the kind in your gut from food). There is a second enzyme called Histamine N-methyltransferase (HNMT) that handles intracellular histamine (the kind your body makes itself).
- Key Insight: DAO supplements only help with dietary histamine. They won’t stop a reaction caused by environmental allergies, stress, or internal histamine release because they don’t enter your bloodstream; they stay in the gut.
4. Natural Plant Sources
While many supplements (like the Solaray brand you mentioned) often use animal-derived DAO (porcine kidney), there are natural vegan sources. Pea shoots, lentil sprouts, and mung bean sprouts are naturally high in DAO. Some people incorporate these sprouts into their diet as a functional food for histamine management.
5. Genetic “Blueprints”
Some people have variations in the AOC1 gene, which provides instructions for making DAO. If you have specific “SNPs” (genetic variations) on this gene, your baseline production of DAO might be naturally lower than average, making you more sensitive to high-histamine foods regardless of your gut health.
6. It’s Not Just for Histamine
DAO is actually a bit of a multi-tasker. It also breaks down other “biogenic amines” like spermidine and putrescine (found in aging meat and some vegetables). If your DAO is low, you might be sensitive to a broader range of food compounds than just histamine.
Foods That are High In Histamine!
Managing histamine levels is often described as “filling a bucket.” You might be able to handle a little bit of high-histamine food, but once the bucket overflows (because of DAO-blocking medications or a high-histamine meal), that’s when symptoms kick in.
Here is a breakdown of the primary “bucket fillers” and the factors that can “clog the drain” by inhibiting your DAO.
High-Histamine Foods to Avoid
Histamine levels in food increase as it ages, ferments, or processes. Freshness is your best friend here.
- Fermented Everything: Sauerkraut, kimchi, kombucha, kefir, yogurt, soy sauce, miso, and sourdough.
- Aged Cheeses: Parmesan, Cheddar, Blue Cheese, Camembert, and Gouda. (Stick to fresh options like Mozzarella, Ricotta, or Cottage Cheese).
- Processed & Cured Meats: Salami, pepperoni, bacon, sausages, hot dogs, and deli meats.
- Specific Vegetables: Spinach, tomatoes, eggplant, and avocados.
- Canned & Smoked Fish: Canned tuna, mackerel, sardines, and smoked salmon.
- Histamine “Liberators”: These don’t have much histamine themselves but trigger your body to release its own.
- Fruits: Citrus (lemons, limes, oranges), strawberries, papaya, and pineapple.
- Nuts: Walnuts and cashews.
- Misc: Chocolate/cocoa and raw egg whites.
Beverages That Block DAO
Some drinks are a “double hit” because they are high in histamine and they actively stop your DAO enzyme from working.
- Alcohol: Red wine, beer, and champagne are the biggest offenders.
- Energy Drinks: High caffeine and specific additives can suppress DAO activity.
- Specific Teas: Black tea, green tea, and mate tea can inhibit the enzyme’s efficiency.
Medications That Affect DAO Levels
Certain drugs can either directly block the DAO enzyme (Inhibitors) or trigger a massive histamine release (Liberators). If you take any of these regularly, they might be the “invisible” reason your histamine bucket is always full.
| Category | Potential DAO Inhibitors / Blockers |
| Antibiotics | Clavulanic acid (in Augmentin), Cefuroxime, Isoniazid. |
| Heart / BP | Verapamil, Alprenolol, Dihydralazine. |
| Pain / NSAIDs | Aspirin, Naproxen, and Diclofenac (often considered “liberators”). |
| Psychotropic | Amitriptyline, Citalopram, Diazepam (Valium). |
| GI / Stomach | Cimetidine (Tagamet) and some older H2 blockers. |
| Mucolytics | Acetylcysteine and Ambroxol (common in cough syrups). |
Note: Do not stop taking prescribed medications without consulting your doctor. Sometimes, simply shifting the timing of the medication or adding a DAO supplement can mitigate the effect.
The “Leftover” Rule
A crucial tip for managing DAO levels is avoiding reheated leftovers. Bacteria begin producing histamine on cooked food the moment it starts to cool down. If you have a low DAO level, a meal that was safe for dinner might trigger a reaction when eaten for lunch the next day.
Pro-tip: Freeze your portions immediately after cooking and reheat them directly from the freezer.
Summary:
Diamine oxidase (DAO) is a vital digestive enzyme responsible for neutralizing dietary histamine in the small intestine before it can enter the bloodstream. A deficiency or inhibition of this enzyme – caused by factors ranging from genetic predisposition and gastrointestinal damage to specific medications, alcohol consumption, and a lack of necessary cofactors like copper and vitamins B6 and C – can lead to histamine intolerance, resulting in allergy-like symptoms across various bodily systems. Managing this condition involves a multi-pronged approach of reducing histamine intake by avoiding aged, fermented, and leftover foods, identifying histamine-liberating triggers, and potentially supplementing with the DAO enzyme to assist in breaking down histamine-rich meals.
Leave a Reply