One discovery about enzyme deficiencies is particularly intriguing, because it may explain the link between hyperactivity in children and food colourings. Hyperactive children appear to be deficient in an enzyme known as phenolsulphotransferase-P or PST-P. This enzyme detoxifies various compounds, including a substance called p-cresol that is produced by bacteria in the gut. No-one has any idea how p-cresol might cause hyperactivity, but it is a phenol, and phenols can be toxic.
What is interesting about PST-P is that it can be inhibited by certain food colourings – in other words, the enzyme no longer works if those food colourings are present. If a normal, healthy child eats colouring of this type in moderation, it will not do any apparent harm because that child’s PST-P is fully active to begin with. But for a child with defective PST-P, the same amount of colouring could reduce the level of PST-P activity to damaging levels.
It is interesting that a high proportion of patients with migraine, who are affected by dietary triggers such as cheese and chocolate, also have a defect in PST-P. Wine, like some food colourings, appears to inhibit PST-P, and this may contribute to the effects of red wine in triggering migraines. It is likely that enzyme defects play a part in migraine, because migraine sufferers tend to be defective for certain enzymes, but exactly what goes wrong is far from clear. The chemicals that are under suspicion of triggering migraine – tyramine and phenylethylamine – are not detoxified by PST-P. Tyramine is detoxified by a related enzyme called PST-M, but this is generally not lacking in migraine sufferers. This is a puzzle that can only be sorted out by more research. For more on enzyme defects in migraine.
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