Dr Janice Joneja, a world expert on histamine intolerance, has created an easy-to-read guide to help you understand whether you might be histamine intolerant, and, if so, what you can do about it.
I am a 41 year-old female who was recently diagnosed with MCAD. I have a much bigger concern than histamine though.
Mast cell activation disease (MCAD) refers to several different conditions, all of which involve abnormally large numbers of mast cells which are subject to degranulation by diverse triggers. Mast cells are white blood cells, mainly located in tissues throughout the body, which produce and store defensive chemicals, called inflammatory mediators, ready to be released in response to a threat to the body. The mediators are stored within granules in the mast cell. The release of the mediators is termed degranulation as the granules are released from the cells. One of the first and most powerful of the mediators is histamine.
However, there are several additional mediators released at the same time, or rapidly thereafter. Degranulation of mast cells is responsible for allergy, so the symptoms of MCAD are the same as in an allergic reaction. Because there is an excessive number of mast cells, there will be an excessive quantity of inflammatory mediators released whenever the cells are activated by diverse triggering events.
However, histamine is only partially responsible for the symptoms of allergy and MCAD, because the additional mediators all have their own unique role to play. Reducing external sources of histamine, typically by following a histamine-restricted diet, or taking antihistamines to reduce the effects within the body, will only alleviate the symptoms mediated by histamine. Symptoms caused by the additional mediators will not be affected, so measures to reduce histamine alone will be inadequate in relieving all of the adverse reactions in allergy and MCAD. Nevertheless, by reducing histamine, many of the most troublesome symptoms can often be reduced to manageable levels.
Dietary tyramine does not usually cause any ill effects, except in people who are (a) taking monoamine oxidase inhibitors (MAOI) drugs, which are principally prescribed for depression, or (b) tyramine intolerant, probably due to a deficiency of the enzyme, monoamine oxidase, which breaks down excess tyramine.
Histamine and Tyramine – what is the connection?
Both histamine and tyramine are biogenic amines. Amines are chemicals derived from ammonia and biogenic means that they are biologically active. Biogenic amines play extremely important roles in the body. Histamine and tyramine are also described as vasoactive amines, which indicates that they can trigger effects in blood vessels, causing vasodilatation (widening) or vasoconstriction (narrowing) of blood cells throughout the body, and thereby affecting blood pressure. However, although there are similarities among such biologically active chemicals, there are many very important differences in their mode of action, and the factors and processes which control their production and their activities.
Function in the Body
Histamine (chemical name: 2-4-imidazolyl ethylamine) is involved in several essential processes including:
Tyramine (chemical name: 4-hydroxyphenethylamine) is involved in the synthesis (production) of catecholamines such as dopamine, epinephrine and norepinephrine which are neurotransmitters in the sympathetic nervous system. The sympathetic nervous system is responsible for the fight or flight response. It is part of the autonomic nervous system, which regulates the body’s unconscious actions.
Both histamine and tyrosine are derived from amino acids. Amino acids are components of proteins.
Histamine is derived from the amino acid histidine by the action of the enzyme histidine decarboxylase.
Histidine and tyrosine are present in proteins from most biological materials including animals, plants and other living organisms.
All biological processes are controlled by a complex series of enzymatic reactions which ensure that exactly the right quantity of every active chemical is produced, maintained, or eliminated, to deliver the precise amount required for its optimal functioning in the healthy body. When there is excess of any biologically active chemical, specific enzymes break down the excess and remove it from the body.
Histamine is broken down by two different enzymes: histamine N-methyltransferase (HNMT) and diamine oxidase (DAO). DAO is mainly responsible for ensuring that excess histamine in the diet is degraded within the digestive tract before it can enter the body. It also acts as a “scavenger” within the body to reduce the amount of unnecessary histamine circulating in blood and tissues.
Tyramine is degraded by monoamine oxidases (MOA) of which there are two subtypes, MOA-A and MOA-B. Usually tyramine in the diet is broken down (metabolized) by MAO-A in the intestinal wall and then in the liver. This destroys excess tyramine before it can be absorbed and enter circulation, where it is converted into norepinephrine.
When the enzyme systems are not able to break down the excess, which may be because of a genetic defect in enzyme production, or reduction of their activities by external agents such as medications, or other factors, the increase in level can lead to adverse effects.
Excess histamine leads to symptoms resembling allergy, because histamine is an important mediator in allergy and many of the symptoms of allergy are a result of the activity of histamine.
If too much tyramine is ingested, excess norepinephrine can lead to a rapid increase in blood pressure. If the increase is large and sudden, a hypertensive crisis can occur, which can cause permanent damage to bodily organs, stroke, aneurysm, and very rarely, death.
Although excess histamine and tyramine are often a result of over-abundance of the amines within the body (endogenous), both can be augmented by sources outside the body (exogenous), which may be derived from foods and beverages in the diet. When the body’s enzyme systems are already deficient, it is important that all means of reducing unnecessary sources of the amines be employed in order to reduce the excess wherever possible. Following a histamine restricted diet will reduce exogenous (from outside the body) sources of histamine, and a tyramine-reduced diet will similarly reduce dietary sources of tyramine. From your short description it is clear that you will need to achieve both objectives.
Biogenic Amines in Food
The good news is that because both biogenic amines are produced by enzymatic breakdown of amino acids, mainly as a result of microbial fermentation, the foods you need to avoid are very similar. In both cases the majority of the restrictions involve avoidance of fermented food products. However, there are individual additional sources of both which need to be considered.
A few important points:
If you found this article interesting, you will find many more articles on anaphylaxis here, and reports of research into anaphylaxis here.