MAOI drugs are widely misunderstood, victimized by outdated and inaccurate information, feared and reviled in much of the professional community. In spite of this, they are extraordinarily effective when used appropriately, and patients are often pleasantly surprised at the extent of the improvements they obtain with their use. Indeed if the reader goes to AskAPatient.com, they score higher than any other class of antidepressants where a significant number of reviews were posted. This blog is being written to provide information to my patients and thus save me endless repetition and to provide the most current information about tyramine in foods because much of the information in the community is inaccurate. This is meant as a supplement to my office handout.
First and foremost, I want to underline the fact that the reaction to tyramine is a quantitative phenomena, i.e., the degree of reaction is proportional to the amount of tyramine ingested. Portion size is definitely important. The amount of tyramine ingested is a product of the concentration of tyramine in the food times the quantity. Properly stored or fresh meat, poultry, or fish are all right. Birds or sausages or other meats that hang for periods in delis should be approached with caution. Smell is something of a guide. The rule of thumb for cheeses is the softer, the older, and the smellier, the higher the tyramine content. Any food whose taste is produced by fermentation should be assessed carefully. Be careful with leftovers. For more information on tyramine restricted foods go to the Grossi's recommended links from the home page of this site. This reaction is the so-called cheese effect or tyramine effect and is characterized by pounding heartbeat, increased blood pressure (usually over 180 mm Hg), slowed heart rate, stiff neck, excruciating headache, tightness in the chest, pallor, diaphoresis, nausea, and confusion. I have found that in these modern times this is a very infrequent occurrence and death is extremely rare contrary to the reported experience in the 1960s. When such a reaction does develop, it generally starts within 20 to 30 minutes. Indeed, if a person on an MAOI ever has a doubt about a food, take a small bite and wait thirty minutes. If no reaction develops, the food is most likely safe. It is likely that modern food handling and the use of standardized starter cultures for foods, such as cheeses, as well as good refrigeration, all play a role in causing this reaction to be rare these days.
In 2006 A. Azzuro and colleagues ran fourteen tyramine pressors tests on healthy unmedicated, fasting males and found that the amount of tyramine needed to elicit a 30 mm Hg rise in systolic blood pressure was between 400 mgm to 600 mgm. When tyramine was given with food that more closely simulates daily life, the amount increased by a factor of almost three. When treated with an MAOI, these thresholds decline substantially. To put these numbers into perspective, a high-tyramine meal contains 40 mgm of tyramine. The foods with the highest tyramine content are soy sauce (remember, it is the key ingredient in most marinades and in sauces from Asian countries) and certain cheeses, especially artisanal cheeses such as English Stilton, Cheddar, Parmigiano, Manchego, Compte, Brie, Camembert, Liederkranz, blue cheeses, Emmentaler, Gruyere, and Edam. Generally, the smellier and the softer and the older, the more the tyramine. Modern food regulations have led to widespread use of starter cultures which do not contain bacteria with decarboxylase enzymes thus preventing the conversion of tyrosine or phenylalanine into tyramine. It should also be noted that long aging in warehouses is not consistent with modern supermarket food management. Fresh unripened cheeses and yogurts have no tyramine, e.g., cottage, ricotta and mascarpone. Be cautious with marmite, sauerkraut, kimchi, and fish sauces, and Spanish dry fermented sausages Chorizo, Fuet, Sobrasada, and Salsichon. Modern commercial beer and wine can be consumed in moderation though tap beer should be avoided as should any home-made or boutique beer. If beer has a sediment or is cloudy when swirled, avoid it. Remember when drinking on an empty stomach the tyramine can be absorbed very quickly and thus a smaller amount is needed to cause some reaction (equivalent to the difference cited above for fasting versus fed study results). Some Belgian beers, especially Lambic style, have high tyramine content and so should be avoided.
For a more complete discussion and tyramine levels in foods please see the article Monoamine Oxidase Inhibitors, Dietary Tyramine and Drug Interactions, an excellent resource maintained and developed by Dr. P. Ken Gillman who has published extensively on this topic. Many thanks to Dr. Gillman.