Cheese syndrome is the name of a condition that is commonly associated with the usage of monoamine oxidase inhibitors (MAOIs), a class of anti-depressants. It is caused by a buildup of tyramine, an amino acid that is involved in blood pressure regulation. Monoamine oxidase inhibitors (MAOIs) are a class of antidepressant drugs prescribed for the treatment of depression. ... An antidepressant is a medication used primarily in the treatment of clinical depression. ... Tyramine (4-hydroxy-phenethylamine) is a monoamine compound derived from the amino acid tyrosine. ... Blood pressure is the pressure exerted by the blood on the walls of the blood vessels. ...

The name of the syndrome is derived of the story of the British pharmacist who first noted the effect. His wife, who used a MAOI at the time, complained of headaches everytime they had eaten cheese, which is particularly rich in tyramine.

MAOIs work by decreasing the action of the enzyme monoamine oxidase, which destroys neurotransmitters like serotonin. Increasing the serotonin concentration in the brain ultimately helps people with depressions. But it turned out the enzyme was also responsible for the breakdown of tyramine, a compound that causes severe discomfort or even death if it builds up to too high a concentration. Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = leaven) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ... Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a presynaptic and a postsynaptic neuron. ... Serotonin (5-hydroxytryptamine, or 5-HT) is a monoamine neurotransmitter synthesised in serotonergic neurons in the central nervous system and enterochromaffin cells in the gastrointestinal tract. ...

The connection drawn by the pharmacist explained why many people had been complaining of headaches while using the medicine, but also why some had died of brain haemorrhages while on the drug. The latter effect had caused MAOI's to be taken off the market for a while, even after the cheese connection was made.

In modern days, MAOIs are prescribed yet again, but patients are told to watch their diet. Red wine, nuts and cheese should not be combined with this particular class of anti-depressants.