Food-Sensitivity Reactions 101

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Hi All,

In another thread, titled MRT question related to diet, Elizabeth posted some questions about testing procedures that I started to respond to, and then the post got so long and convoluted, that I decided to post it as a separate topic.

Regarding her situation, theoretically, the optimum way to test for an egg sensitivity, or any other food sensitivity, (other than gluten), is to eliminate them from the diet, until at least 5 or 6 symptom-free days have passed, and then challenge the immune system with the food item. If you're sensitive to the food, at least 5 or 6 days of abstinence will allow the antibody level to decline substantially, so that when you do the challenge, your immune system will be at a heightened sensitivity level, so that you will get a maximum reaction response, (if you're sensitive to the food), and no response, if you're not sensitive to it. That enhanced difference in responses makes it easier to detect a clear distinction. This works because the half-life of IgA antibodies is roughly in the 5 to 6 day range, so after 5 or 6 days without any source of inflammation, the IgA antibody level should be down to roughly half of what it was before eliminating the food from the diet, and if the immune system is challenged at that point, it will perceive the sudden rise in antibody level as a serious threat, and it will respond accordingly.

The same thing can be done with gluten, except that the half-life of anti-gliadin antibodies is much longer than the half-life of most other food-based antibodies, so it takes much longer for them to fade away. This is illustrated by the fact that Enterolab can reliably detect anti-gliadin antibodies for at least a year after gluten is withdrawn from the diet, and anti-gliadin antibodies can sometimes be detected as long as 2 years after gluten has been withdrawn from the diet. Antibodies to casein, soy, eggs, etc., however, decline relatively quickly, so that the respective Enterolab tests can reliably detect those antibodies for only approximately 5 or 6 weeks or so, at best, after the corresponding foods have been withdrawn from the diet. As a result, much more time must elapse, (on the order of weeks, or better still, months, rather than days), after removing gluten from the diet, before a gluten challenge can be done with maximum effectiveness.

Looking at this another way, consider the classic celiac anti-gliadin antibody, (AGA), blood test. In these tests, both IgA and IgG antibodies to gliadin are included, and the AGA level is determined by an enzyme-linked immunosorbent assay, (ELISA), or by radioimmunoassay. Results of these tests are compared with a "standard" test "threshold", or breakpoint, set at whatever number below which approximately 85% of a normal population will show a lower test result. IOW, any test result at or above that breakpoint represents a positive test result, (indicating the presence of disease), and any test result below the breakpoint represents a negative test result, (where disease is not indicated). It appears that the stool tests at Enterolab are done basically the same way, (using stool instead of blood), except that only IgA antibodies are considered, so this analysis may not exactly correlate for the tests offered by Enterolab, though the results should follow a similar trend.

Most people naturally assume that once we remove the offending food from the diet, the antibodies should disappear virtually immediately, but that can't happen with gluten, because the half-life of anti-gliadin antibodies is approximately 120 days. The way that anti-gliadin antibodies are normally depleted, is by their attachment to gluten, so they are removed from the system as the gluten passes out of the body. And, of course, new antibodies are produced, as additional gluten is ingested. With gluten removed from the diet, however, this mechanism is no longer available to remove antibodies from the existing supply, so that even though no new antibodies are being added, the half-life of the existing antibodies becomes the determining factor to predict the decay rate of the antibodies from the system. IOW, they have to decay, and disappear due to natural attrition. This means that in 4 months, (120 days), the antibody level should be exactly half of what it was initially, (theoretically, at least). In another 4 months, it should be halved again.

It's immediately obvious that if an individual starts the diet with a very high initial antibody level, it will take a long time for the antibody level to decline to below the trigger point. In fact, for a test result numbering in the hundreds, theoretically, it should take a year or two, or more, for the antibody level to fall below the threshold level for a negative test indication. If the diet is compromised at some point, and gluten is introduced, (either intentionally or accidentally), the antibody level will be kicked to a higher level again, (how much will depend on how much gluten is ingested, and for how long), so that the antibody decay countdown will have to be reset. This long half-life is why gluten reactions are so persistent, and why they take so long to bring under control. Obviously, test scores do count, and this is why some individuals take so much longer to reach remission, than others. Accidentally ingesting gluten, of course is the wild card, and can really throw a monkey wrench into the predictions concerning recovery time.

This is just my analysis of the situation, based on the half-life of gluten antibodies, so I can't guarantee that this is a scientifically-defensible explaination, but our experience here on this board seems to bear this out, in view of the fact that people who have been reacting for years, seem to take much longer to get their symptoms under control, and anyone who has been faithfully following the diet for a few months, and then accidentally ingests gluten, always seems to experience a much more severe reaction to gluten, than they did early on. In general, it seems to take "forever" to establish remission from a gluten-sensitivity, whereas many members have found that once they have been on the GF diet for a sufficiently long time, eliminating another reactive food from their diet usually brings a relatively fast response, often in less than a week. IMO, that's due to the huge difference between the long half-life of antigliadin antibodies, and the relatively short half-lives of antibodies to other proteins, such as casein, soy, yeast, eggs, etc.

At least that's how I see it.

Tex