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Dr Joneja's Guides to Histamine Intolerance
Dr Janice Joneja, a world expert on histamine intolerance, has published two books on histamine intolerance: A Beginner's Guide to Histamine Intolerance – read more about it here. Buy the paperback from Amazon here; buy the e-book from Amazon here. Histamine Intolerance: The Comprehensive Guide for Healthcare Professionals – read more about it here. Buy the ebook from Amazon here. You can buy all of Dr Joneja's books here in the UK or here in the US. |
Diamine Oxidase (DAO): what you need to know |
Dr Janice Joneja is constantly asked about DAO about which there is a great deal of misunderstanding. Here is her DAO primer. |
We receive many enquiries about diamine oxidase (DAO) about which there is a great deal of misunderstanding. The questions asked are usually some version of the following:
For those readers new to the field, a few words about diamine oxidase (DAO) is in order. Histamine intolerance or sensitivity is caused by a build-up of histamine in the body to a level that exceeds the amount required for normal functioning. The excess histamine results in symptoms that resemble allergy. Under normal conditions, excess histamine is broken down by specific enzymes, especially diamine oxidase (DAO). The products of histamine breakdown are then excreted via the kidneys in urine. Usually this will ensure that histamine levels do not exceed a person’s “limit of tolerance” (the level above which symptoms develop). However, when the amount of DAO is insufficient to deal with the excess, histamine levels rise and typical histamine sensitivity symptoms develop. Please see this article. DAO acts on histamine both inside and outside the body. Within the body, DAO is found principally in the kidneys, thymus, and the placenta in pregnant women. When histamine levels inside the body become excessive, DAO, and another enzyme called histamine N-methyl transferase (HNMT) break down the excess. Excess histamine can rise inside the body (called endogenous histamine) as it is released from mast cells in a number of conditions including allergy, mast cell activation disorders, chronic inflammation, infection, and trauma, among others. The digestive canal is essentially an area outside the body as materials enter at one end and exit at the other. Only the digested products enter the body through the epithelium and pass into circulation. DAO is found in the ileum and jejunum of the small intestine. It mixes with food, beverages and other ingested materials as they pass through the digestive tract. As the DAO encounters histamine in these substances, it breaks it down, thus preventing this external source of histamine (called exogenous histamine) from entering the body. When DAO is adequate and functioning efficiently, almost 99% of exogenous histamine is broken down within the digestive tract lumen and removed before it can enter the body. It is estimated that only about 1% of histamine from this source actually enters circulation. When DAO is deficient, far more histamine enters and builds up within the body. DAO supplements are designed to increase the DAO in the digestive tract and enhance breakdown of histamine within the contents of the digestive canal. Unlike supplements of vitamins, minerals and other nutrients, DAO does not enter into circulation and therefore will not increase the amount of DAO inside the body. DAO must be taken very shortly before meals as it has a short “half-life” - the time it takes for the enzyme to become inactive. Its effect is limited to the degree of breakdown of histamine in the dietary components with which it is mixed for a fairly short as the food passes through the digestive canal. Obviously, the amount of histamine entering the body from dietary sources can be significantly reduced by following a histamine-restricted diet. (See the second half of this article.) A low-histamine diet, plus supplemental DAO should reduce the amount of exogenous histamine entering the body to almost nil. It is very important to understand that supplemental DAO and a histamine-restricted diet will not reduce the amount of histamine produced within the body. The effects of this histamine must be addressed by other methods of control such as antihistamines, allergy management programs, mast cells stabilizers and other appropriate therapies depending on the source of the endogenous histamine. Now to address the specific questions listed above:
August 2016 You can buy DAO supplements here in the UK or here in the US. If you found this article interesting you can find a number of other articles on histamine intolerance both by Dr Joneja and others here, reports on histamine research here and a Q & A section on histamine with Dr Joneja here. For many, many other articles on every type of food allergy and intolerance click here; for coeliac disease and other food related conditions, go here. To sign up for our FREE fortnightly e-newsletter, go here. Dr Janice Joneja, Ph.D., RDDr. Janice Joneja is a researcher, educator, author, and clinical counsellor with over thirty years of experience in the area of biochemical and immunological reactions involved in food allergy and intolerances. Dr. Joneja holds a Ph.D. in medical microbiology and immunology and is a registered dietitian (RD). |