Paper: McQueen J, Loblay R, Swain AR, Anthony M, Lance J. A controlled trial of dietary modification in migraine. New advances in headache research. Smith-Gordom; 1989. p. 235–42.
Overview of paper: This trial follows on a study of food intolerance in 237 migraine patients presenting at a food allergy clinic [1]. In the original study (elimination diet/double blind placebo-controlled food challenges), 48% reacted to at least one chemical challenge, such as nitrates, preservatives, salicylate, amines, MSG, or tartrazine; four years later, a large number of these patients continued to follow an appropriately-restricted diet and considered themselves substantially improved.
In the current trial, participants were recruited from a migraine clinic instead of a food allergy clinic. Only 19 of 95 participants completed both the food challenge and the modified diet crossover trial (4 weeks normal diet, 1 week washout, 4 weeks trigger-free diet): “only half experienced a significant improvement on the appropriate [trigger-free] diet, and only three were headache-free altogether.”
The quote:
[E]ven in patients in whom dietary triggers may have been identified by double-blind challenge, long-term avoidance of the relevant foods is likely to be effective as a prophylactic measure only in a minority of patients. This should not be taken to mean that patients who incriminate particular foods as triggers must be mistaken. The situation is comparable to that in asthmatics where it has become abundantly clear that some patients are sensitive to the effects of salicylate, MSG and sulphite preservatives. Large doses may sometimes precipitate acute attacks, but regular avoidance of foods containing these substances does not usually produce measurable clinical improvements in the long term [2]. No doubt, in asthma as in migraine, this reflects the multitude of other intrinsic and extrinsic factors involved in the triggering of symptoms in predisposed individuals.
Significance of quote: This study has definite limitations, including a small sample size, a greater placebo response rate than normal, a short washout period (and possible order effect), and dietary compliance issues. The write-up is also short on experimental details, especially regarding the order of the two test diets. However, perhaps some of these problems mirror the real-life difficulties that people face when trying to manage migraines that can often be linked to food. Secondary triggers – lack of sleep, menstruation, bright lights, motion sickness, fragrances, etc. – can be at least as or even more important than food on any given day. This is not to say, though, that migraine (and asthma) sufferers should freely consume the foods that they know to be triggers, only that the complete avoidance of trigger foods may not be necessary for certain people.
References
1. Loblay R, Swain AR. Food Intolerance. In: Wahlqvist ML, Truswell AS, editors. Recent Advances in Clinical Nutrition. London: Libbey; 1986. p. 169–77.
2. “After 3 months on the restricted diet, four of 19 children on the MBS[metabisulfite]-free diet and one of six on the salicylate-free diet had objective signs of improvement, namely, reduction in asthma medications and/or improvement in lung function.”
Towns SJ, Mellis CM. Role of Acetyl Salicylic Acid and Sodium Metabisulfite in Chronic Childhood Asthma. Pediatrics. 1984 May 1;73(5):631–7.