Chocolate is one of the few foods which has been investigated in double blind controlled studies, to determine how much of a trigger it really is - unlike many other food products, which have merely been included as part of larger studies using a wide range of possibilities.
These double blind, focused studies, apparently left ambiguity on the subject. A 1974 study undertaken at the London Hospital apparently concluded that whilst chocolate may be a trigger, it wasn't a significant one(2). This was a full five years prior to the Lancet study, which ranked chocolate near the top of the list along with other triggers, considered predominantly to cause migraines.
Another study done in 1997 also used a double blind protocol and placebo to try and pinpoint chocolate as an aggressive migraine trigger - again with inconclusive results. The study, carried out at the University of Pittsburgh, Pain Evaluation and Treatment Institute, concluded there was no difference between patients given chocolate and others given the carob placebo in either occurrence or severity of migraines(3).
Of course, one must take into account the overwhelming amount of anecdotal and testimonial evidence from hundreds of thousands of migraine sufferers who report chocolate as a trigger. Many of these claim that removing it from their diet caused instant cessation - whereas accidental or careless reintroduction caused just as immediate recurrence of symptoms.
There does exist an unpublished study, on which correspondence exists, involving a trial with 20 patients who, believing chocolate to be a migraine trigger, were subsequently challenged with either chocolate or a placebo. The 8 receiving the placebo had no incidence of migraine - five out of the 12 who received chocolate did have a typical migraine attack. The small number of people in the test group meant that the subsequent results were not completely conclusive.
As is so often the case with food intolerances, what one person can eat without an ill-effects, can create an unpleasant or even harmful reaction in another. Consider the simple peanut - a killer for some, a harmless snack for another.
Obviously scientific studies are interesting and essential, but however much we crave it, chocolate is something we can live without. The most effective method to discover if it's a trigger food for the individual, is to cut it out from their diet for a few weeks. If your migraines are bad enough, it's a simple sacrifice to make.
(1) Grant ECG; Food, Allergies and Migraine; Lancet, May 5 1979;966-969
(2) A. M. Moffett, M. Swash, and D. F. Scott - Neurol Neurosurg Psychiatry. 1974 April
(3) Marcus DA, Scharff L, Turk D, Gourley LM - Cephalalgia 1997 Dec; 17(8):855-62
(4) CM Gibb, V Glover, M Sandler, Bernhard Baron Memorial Research Laboratories
