Diamine oxidase (DAO) is a gastrointestinal enzyme that breaks down the histamine found in foods such as fermented foods and beverages, and cured meats. Leftovers that are spoiling are also high in histamine because of bacterial histamine production.
Alcohol and some medications can trigger histamine as well, contributing to unpleasant symptoms if the body is unable to break down the histamine.
An insufficiency of DAO can lead to histamine intolerance (HIT), characterized by gastrointestinal symptoms including abdominal pain, bloating, and diarrhea. However, other symptoms are common as well including headache, itching, flushing, nasal congestion, red eyes, asthma, low blood pressure, and even cardiac arrhythmias. HIT may overlap with other GI disorders including inflammatory bowel disease, celiac disease, dysbiosis, and small intestine bacterial overgrowth.
The most effective way to deal with HIT is to avoid histamine triggers and histamine-containing foods. However, supplemental DAO is available in vegetarian and animal-derived forms and can help break down ingested histamine if symptoms persist.
It is also important to support the production of DAO in the intestine by consuming adequate vitamin B6, vitamin C, and copper. These nutrients are needed for DAO synthesis.
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