Food Intolerance Testing and Migraine
In the first study of its kind, 61 people with moderate to severe migraines were given a food intolerance test. Only one patient had no intolerances at all and the average participant had 5.3. Of those who eliminated the named foods from their diets, 80 per cent reported some improvement in their migraines and more than a third reported significant relief. More than 60 per cent of patients who reintroduced the suspect foods into their diets reported the return of their migraine symptoms.That is one interpretation of the poster that was presented at a conference: A Prospective Audit of Food Intolerance Among Migraine Patients in Primary Care Clinical Practice (pdf). However, Lantin has omitted the fact that only 39 of the original 61 people completed the 2 month study. The claim that "80 per cent reported some improvement in their migraines" is a little puzzling unless Lantin has had access to an analysis of a sub-group because the authors report the finding that:
After two months, 38.2% of patients reported considerable benefit (scoring 4 or 5), while 32.4% reported little or no benefit (scoring 0 or 1). [Emphasis added.]There is no attempt to explore the difficulty that people may have had in following an IgG-guided elimination diet and whether this is a possible explanation for the discrepancy between the 61 people who were audited for the study and the 39 who completed the 2 months. The authors report that 56% of the migraineurs "changed their diets 'a lot'" and 33% "made a ‘reasonable attempt’ to change their diet". There is no exploration of "a lot" or "reasonable attempt": the reader does not know whether the former successfully excluded all of the foodstuffs that had returned high IgG levels or not.
Rees and colleagues report that:
[o]ver 60% of patients who reintroduced the suspect foods back into their diets reported the return of their migraine symptoms.However, it is not too surprising that 60% of patients who believe that IgG levels are indicative of food intolerance would experience a return of symptoms if they knowingly ate a 'suspect' food. The percentage of those who report a return of symptoms is inline with the findings of some nocebo studies: if study participants believe that an intervention or substance can harm them, then some of them will report that effect, even in the presence of an inert substance or stimulus. E.g., a study into the psychologic induction of pain found that:
[m]ore than two-thirds of an unselected sample of 34 college students reported mild headaches when told that a (nonexistent) electric current was passing through their heads.For the migraine study, the authors conclude that:
[t]his investigation demonstrated that food intolerances mediated via IgG may play a part in the development of migraine attacks and that changing the diet to eradicate specific foods is a potentially effective treatment for migraine. Further large controlled clinical studies are warranted in this area.However, although these findings are interesting, they do not indicate that food intolerances are mediated by IgG. The authors do not comment on the possible influence of the placebo or Hawthorne effect on their results.
Lantin acknowledges that IgG testing may have "no significant role to play" and writes that:
Food intolerance is only one possible cause of migraine and, even when it is implicated, may not be the only factor. Stress, exercise, travel and the menstrual cycle can also play a part.However, she quotes one of the study's authors, Dr. Andrew Dowson, as saying:
[t]he fact that something is not at the forefront of medical science now does not mean it isn't important - it may just mean we haven't noticed it yet...There is still no published body of evidence to support IgG testing in the diagnosis of food intolerance: relevant professional organisations say IgG tests can not be recommended for that purpose. It was a very short study with a small number of participants. The reported results are within limits for what is known about both the placebo and nocebo effect. I would suggest that there is a potential for harm if people with migraine are encouraged to take a test that has no scientific support: should this intervention fail, then it can lower the bond of trust between the patient and healthcare worker and, through the nocebo effect, may have an adverse impact on the experience of future medical interventions.
This was a pilot study and we need some more definitive research. For example, a placebo-controlled trial that follows up people over the longer term. But it is an interesting piece of work, with encouraging results, and I see no reason why people with migraine should not take a test.
As I've outlined in other posts, there may be a range of consequences for children who follow a restricted diet, particularly ones that eliminate foods that are a significant supply of calories or nutrients or are so restrictive that they cause significant social difficulties.
Truthiness and referenciness make the case for IgG food intolerance tests
More allergy and intolerance testing nonsense: part 1
More allergy and intolerance testing nonsense: part 2
Quote Mining and Misrepresentation: Poor Ways to Claim Clinical Validation or Sound Science
What is the Significance of IgG Antibodies and Testing?
Why IgG Testing for Food Intolerance Is Not As Simple As ABC or Doh Ray Mi