What is DAO deficiency?

DAO deficiency

It is a change in the metabolism of food histamine that occurs when the activity of the enzyme diaminoxidase (DAO) is low, in other words, when due to certain causes (genetic disorders, diseases and the consumption of certain drugs) there is a significant deficiency in the functional activity of the main enzyme acquired in the catabolism of histamine.

In healthy people, histamine in the diet is degraded by the enzyme diaminoxidase (DAO), however, in people with low activity of this enzyme there is a risk of an accumulation of histamine in serum, mentioned until recently as “histamine intolerance“.

This term is a concept that today we consider simplistic, once the extent of the deficiency of DAO and its higher prevalence in the population is demonstrated, since the increased circulating histamine occurs not, in fact, by an intolerance, but by a silent accumulation, without temporal relationships between the dietary intake of histaminic foods and the onset of symptoms.

The imbalance between the histamine ingested with food and the histamine released from the cells of the body that produce and store it and the ability to degrade the surplus histamine leads to the accumulation of histamine in the plasma and the appearance of adverse effects on health.

Differentiating symptoms from Histamine Intolerance

Unlike food allergy, the appearance of symptoms can not only be related to a wide variety of foods with different histamine content, but symptoms can also appear after ingestion of products with a low level of histamine. This imposed considerable difficulties in establishing a maximum tolerable dose; in fact, there is no clear consensus on this threshold. Values ranging from 50 μg of histamine (in a 125 ml serving of wine, for example) to 60-75 mg, after pure histamine administration, were listed as triggers of symptoms of DAO deficiency.

Due to the wide variety of symptoms produced by DAO deficiency, which are chronic pathologies with a high prevalence in the population, immediate research and progress on its origin and possible food management are needed.

The most common symptoms derived from DAO deficiency

It is not necessary for all the symptoms to manifest themselves in a patient, although most individuals with low functional activity of DAO show on average three of these symptoms, migraine being the predominant manifestation.

Clinical data indicate that 20% of patients experience only one or two of these associated symptoms, 41.3% of patients experience 3 or 4 of these symptoms, and 33.8% manifest more than 5.

The most common symptoms derived from DAO deficiency are:

• Migraine and other vascular headaches.
• Gastrointestinal disorders, especially those associated with irritable bowel syndrome, such as constipation, diarrhea, satiety, flatulence or feeling of swelling.
• Dermatological disorders, such as dry, atopic skin, redness of the face or psoriasis.
• Pain in soft tissues, usually diagnosed as fibromyalgia.
• Chronic fatigue, lack of concentration.
• In childhood and adolescence, DAO deficiency was linked to attention deficit disorder and hyperactivity disorder (ADHD).
• Bronchial asthma, wheezing, rhinorrhea.
• Less often, cardiovascular symptoms may appear, such as arrhythmias (palpitations), arterial hypotension or, in some cases, persistent dysmenorrhea (menstrual pain), for years.

Histamine pathway in the body

In the metabolism of exogenous, food-derived histamine, the DAO enzyme intervenes by degrading it at the intestinal level and converting it into an inactive compound called N-acetyl aldehyde imidazole. The deficiency of the activity of the enzyme in the cells of the intestinal mucosa causes the accumulation of food histamine that crosses the intestine and reaches the bloodstream.

In this way, histamine from the diet enters the bloodstream, increases the total plasma concentration of histamine and spreads throughout the body, producing the well-known harmful effects.