[FoRK] Suicide-by-Stilton: some bits on MAOI antidepressants

Rohit Khare < rohit at commerce.net > on > Mon Mar 6 09:31:22 PST 2006

Edited from: http://www.otago.ac.nz/humannutrition/dietetics/Summary% 
20of%20Findings/APotter.pdf

Monoamine Oxidase Inhibitors (MAOIs) were
the first effective antidepressant drugs. Since
their introduction in the 1950s they have
largely been surpassed by other medications
with fewer side-effects. However for a minority
of patients they are very effective drugs and in
fact the only medications that work.

Dietary monoamines are normally inactivated
as they pass through the gastrointestinal tract
by monoamine oxidase enzymes (MAO).

Only 12% will reach the bloodstream in
unmedicated individuals. The MAO enzymes
are inhibited during MAOI treatment, allowing
the majority of ingested amines to pass
through the intestinal wall intact. If vaso-active
amines are ingested in large enough
quantities, these can displace noradrenaline
from nerve terminals, triggering an acute
hypertensive reaction.

* The mechanism of the ‘Cheese
Reaction’

The first substance in food recognised as
having this effect was tyramine in cheese.

The first patient to die during MAOI therapy
had recently consumed a Stilton sandwich.
Therefore this became known as the
‘Cheese Reaction’.

Symptoms include
* Sudden onset headache
* Sensitivity to light
* Sweating, shivering, chills
* Rapid heartbeat
* Intracerebral haemorrhage
* Coma
* Death

Tyramine requires three factors to form:
* Free amino acids
* Bacteria with decarboxy-lating activity
* Conditions favourable to bacterial
growth

Five patients consented to take part in the
project. They were interviewed individually
and in their own homes if appropriate. All had
been taking the MAOI antidepressants
Parnate or Nardil for at least 12 months.
Most patients reported not strictly complying
with the diet. The food most commonly eaten
against advice was cheese. Patients
perceived that mild- tasting cheeses were
safe.

Only one patient was aware of having
experienced headaches in relation to
eating specific foods. Two patients were
completely unaware of why they should
follow a diet at all.

Any protein-containing food can theoretically
become high in tyramine. As proteins age
they degrade, freeing their component amino
acids. If bacteria are present with
decarboxylating activity, these then act on free
tyrosine and convert it to tyramine. If
conditions are favourable, this reaction keeps
occurring and the tyramine content of the
food continues to rise.

In practice this applies mainly to foods which
are aged or fermented to improve flavour -
such as cheese and salami, but also

Formation of Tyramine

The following foods were named on the
revised card:

* All aged cheeses, including edam
and mild varieties. Cheese has been linked
to over 80% of the reactions reported
between MAOIs and food, and the majority of
deaths.

Un-aged types such as fresh ricotta, cottage
and cream cheese are unrestricted.

* Meat and fish which isn’t fresh,
including matured game and leftovers.
Safe food handling is especially important for
patients taking MAOIs. Food should only be
eaten while it is fresh and tinned food
consumed the day it is opened

* Salami and air-dried meats. These
have never been implicated in a case
reaction but can contain very high levels of
tyramine

* Soy sauce and soy products such
as tofu and miso. The tyramine content of
these products has been shown to vary
widely between brands and will increase with
age of product.

* Tap and homebrewed beer. Beer
provides all the conditions required for
formation of tyramine. If  lines between keg
and tap aren’t kept clean they may allow beer
to become contaminated, and homebrew
conditions can not be guaranteed.

* Yeast extracts such as Marmite,
Vegemite and Bovril. These have caused
several reactions and are consistently high in
tyramine.

* Broad bean pods, sauerkraut and
banana skins contain high levels of other
pressor amines and should be absolutely
avoided. Broad beans and banana flesh are
completely safe.


The following foods were omitted from the
revised card:

* Sustagen. The primary ingredient of
Sustagen is milk powder. The basis for this
restriction is a case report of a young woman
taking a powdered protein supplement to aid
weight loss. This product had added herbs
and ‘botanicals’ that may have actually been
responsible for the resultant hypertension

* Packaged and convenience foods.
This restriction appears to be based on the
same report. Unlike Marmite and similar
products, yeast extracts used in convenience
products are autolysed without fermentation,
and contain no tyramine. Some products
contain soy sauce powder but in tiny amount
that could not contribute enough tyramine to
initiate the reaction

* Raspberries. These do not appear to
have ever caused a reaction, although there
is a hypothetical risk or a reaction if a large
quantity of non-fresh berries were eaten

* Chianti. One author in 1964 reported a
high tyramine content in Chianti wine. This
has never been replicated and the
production of Chianti has since been
modernised. Chianti contains similar levels of
tyramine as other wine and beer and does
not need to be named.

* Chocolate. Theobromine in chocolate
may cause a headache in susceptible
individuals. This is not a result of an increase
in blood pressure and will not lead to a
hypertensive crisis. Chocolate contains no
tyramine.

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