Biological Therapies in Psychiatry Alan J. Gelenberg, M.D. Dr. Bob's Psychopharmacology Tips

MAOI Diet Update

From time to time, we review new information on diet and medication restrictions that must be followed by patients who take monoamine oxidase inhibitors (MAOIs) (BTP 1994; 17: 18-19, 27-28, 1993; 16: 3, 1990; 13: 9, 1988; 11: 1, 25, 1987; 10: 19, 1983; 6: 43). Recently, Walker and others used liquid chromatography to assay food products that have been on the forbidden list for patients taking these drugs. (1) They measured concentrations of tyramine, a metabolite of the amino acid tyrosine and the pressor in foods most commonly associated with hypertensive reactions in MAOI-treated patients.

Several qualifiers are worth noting at the outset. As the authors show in this study and in previous work, tyramine content can vary widely from brand to brand or, in some foods, even from batch to batch. Of course, the amount of the food ingested makes a difference, and these investigators report wide intraindividual variations that may reflect differential rates and magnitudes of absorption. Freshness is also a variable: as foods ripen and age, metabolic degradation typically occurs, potentially elevating pressor concentrations.

Chianti wine often is featured prominently on the restricted list for MAOI-treated patients. However, in this study -- as in earlier reports -- no tyramine was found in the sample assayed.

Cheese has been associated with the greatest number of hypertensive crises in MAOI-treated patients. Previous analyses have demonstrated high tyramine contents in a wide variety of aged cheeses. In this study, investigators found negligible amounts of tyramine in mozzarella cheese and in the packaged cheese powder used in a popular macaroni and cheese product. They note similar reports of low tyramine concentrations in cottage, cream, ricotta, and processed cheeses.

Only small amounts of tyramine were found in a bottle of Beck's beer. The authors note, however, their previous finding of "alarmingly high tyramine concentrations" in tap beers (BTP 1994; 17: 27-28). Banana peel reportedly contains high concentrations of several vasoactive substances, as well as tyramine. Tyramine content of the pulp itself increases as the banana ripens, but these researchers found that even after prolonged storage, the pulp did not contain dangerous amounts of tyramine. Raspberries -- fresh, frozen, or in jam -- appear safe.

Fresh chicken liver contains modest amounts of tyramine. As it ages, however, (in the refrigerator or, worse still, unrefrigerated) the tyramine content can soar to dangerous levels for MAOI-treated patients.

Fresh meats, including sliced, cold delicatessen meats, generally contain low tyramine concentrations. Aged and cured meats, however, such as salami, pastrami, and sausages, contain wide ranges of tyramine -- including some very high levels. Sausages may contain microorganisms that convert tyrosine to tyramine, so those that are air dried can develop dangerous amounts of the pressor. The authors also found dangerously high levels of tyramine in sauerkraut and soy sauce. A Toblerone chocolate bar, however, contained neither tyramine nor phenylethylamine but did contain significant quantities of the stimulants theobromine and caffeine.

The treatment of any disease, especially a chronic and recurrent condition, requires teamwork. Arrayed against the illness should be all caregivers, as well as the patient, family, and significant others. The patient's greatest likelihood for safe and successful treatment will emerge from a team that is educated about the disease and the therapies. At no time is safety more dependent on knowledge than when an MAOI is part of the treatment. For many patients, the nonselective and irreversible MAOIs currently available by prescription (phenelzine [Nardil] and tranylcypromine [Parnate]) can provide benefits unavailable from any other agent. But understanding potential hazards -- including medication and food interactions -- is essential for safety.

One reversible inhibitor of the isoenzyme MAO-A, moclobemide (Manerix), is available in Canada and many other countries but not, as of now, in the United States. Patients taking moclobemide can tolerate relatively high quantities of tyramine without suffering from hypertension. But many experienced clinicians remain unconvinced that moclobemide is equal in efficacy to the irreversible MAOIs.

1. Walker SE, Shulman KI, Tailor SAN, Gardner D: Tyramine content of previously restricted foods in monoamine oxidase inhibitor diets. J Clin Psychopharmacol 1996; 16: 383-388.

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Original article copyright 1997 Biological Therapies in Psychiatry.
Web page copyright 1998 Robert Hsiung.