FALSE FOOD ALLERGY

Posted on Monday, April 20th, 2009 at 11:10 am

False food allergy, as used in this book, means unusual reactions to food that are caused by the foods triggering mast cells directly. In other words, these reactions involve mast cells but they do not depend on IgE antibodies being formed to the food in question. Because the reaction is produced by mast cells releasing mediators, the symptoms are indistinguishable from true IgE-mediated food allergy.

When food bites back

Food is not necessarily the nice, passive, innocuous stuff that we have traditionally believed it to be: neither plants nor animals want to be eaten, and they have ways of fighting back. In plants, particularly, there are many chemical weapons to deter would-be diners, and some of these chemicals persist, even in modern crop plants. That we are not made ill by them more often is a tribute to our own abilities in breaking down such chemicals – abilities that have been acquired in the course of evolution.

One particularly cunning type of chemical weapon turns the body’s most potent defence force on itself: it fools the mast cells into degranulating. There are dozens of different substances found in food that can perform this trick. Some bind to IgE molecules, effectively bridging two adjacent molecules, in much the same way as an antigen might bridge them. Others bind to the receptors on the mast cell that normally attach themselves to IgE, thus bridging the receptors. Because bridging of the IgEs (and thus bridging the receptors) is the signal for the mast cell to degranulate, both types of substance cause the release of damaging mediators such as histamine. Other substances may produce the same effect simply by binding to the mast cell membrane and

changing its structure so that it becomes more permeable.

One group of compounds that can have this effect on mast cells are the lectins. They are produced in particularly high concentrations by peanuts, beans, peas and lentils, all of which are members of the legume family of plants. Lectins are also found in edible snails, and in wheat, where they may be responsible for producing coeliac disease.

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