Chocolate, cheese and citrus fruit are the most frequently cited provoking factors to which patients ascribe their dietary migraine. We review here the evidence that the monoamines they contain, particularly tyramine, might be causative and conclude that the case remains open. There is no evidence that patients classifiable within this particular subgroup of the disease have a deficiency of the monoamine metabolizing enzyme, monoamine oxidase.

We report the new finding that dietary migraine patients have a relative deficiency of the enzyme, phenolsulphotransferase P, compared with non-dietary migraine patients or controls. Phenolsulphotransferase is particularly active in the intestine where it probably serves to detoxify phenols by adding to them a sulphate group. The enzyme exists in two forms, which we have designated M and P. The M enzyme acts on monoamine phenols such as noradrenaline and tyramine. It is also somewhat reduced in dietary migraine but less significantly so than the P form. No endogenous substrate for the P enzyme has yet been identified but it acts on phenol itself and presumably also on a range of unknown phenols in chocolate, cheese and citrus fruit which are important "triggers" for dietary migraine.