How a disturbed gut flora might produce food intolerance is not known. One possibility is that the gut wall becomes irritated by toxins that the bacteria release – so that more undigested food molecules get through. Those food molecules might then provoke an immune reaction or have some other effect – as exorphins, for example.
Alternatively, the ‘bad’ bacteria might feed on chemicals found in particular foods, and then produce toxins which provoke the symptoms. Because the bacteria favour certain foods, it would be those foods that cause the symptoms. This explanation is more attractive, in some ways, because it does not re- quire any other mechanism to produce the symptoms. But whether it can explain the very specific reactions to food often seen in food intolerance – a sensitivity to oranges and beef but to no other fruits or meats, for example – is another matter. At present there is little evidence on this point, but it is something that Dr Hunter is investigating.
It is certainly true that bacteria can produce damaging toxins – indeed, the normal gut flora produces such chemicals. The role of p-cresol in hyperactive children is described above. A peptide produced by bacteria apparently plays a part in Crohn’s disease, by attracting immune cells into the gut (see pll4). In both these cases, it looks as if the same bacteria are producing the same products in everyone – but healthy people have enzymes to break these bacterial products down. The person who is made ill by them has enzyme defects.
Where there are disturbances of the gut flora, with abnormal bacterial toxins, enzyme defects might also be a factor. Lacking certain detoxification enzymes could make the effects of the disturbed gut flora a great deal worse. In other words, it could be a combination of defects that produces the symptoms.
One element of the gut flora that can become over-represented is a yeast known as Candida. The role of Candida in food intolerance is controversial, and very complex.
*307\180\8*
