"The often-quoted position that 'the relationship between diet and hyperactivity has not been proven' was based on research in the 1970's. It is now timely to consider the useful studies of the 1980's and 1990's that clearly show a relationship."
The paper follows the history of the studies, from the early, somewhat
crude versions, to improved methods which were introduced, starting
in the mid 1980s.
The earlier studies looked for changes in hyperactivity and learning
tasks, but in later studies reports from parents showed that other
symptoms changed. Sleep disturbances were often mentioned by parents.
"Symptoms
which may change include those seen in attention deficit disorder
(ADD) and attention deficit hyperactivity disorder (ADHD), sleep problems
and physical symptoms with later research emphasizing particularly
changes in mood....An important unexpected finding is the number of
researchers who emphasize that the symptom most affected by diet is
mood, especially irritability."
Newer studies were designed to avoid some of the serious shortcomings
of the earlier trials, including the potential for `placebo effect.'
and the size of the population studied. "The numbers [of children]
studied in the recent studies collectively are significant. Diet
establishment time was considered and the period on diet was longer,
as were the challenge phases and wash-out periods. With these changes
in study design the problems of order effect in earlier studies were
resolved."
"The most important finding was that in almost all studies there
was a statistically significant change in behaviour with dietary intervention. A
degree of change was noted with partial and full responses occurring
rather than the all-or-nothing earlier expectation."
Later study designs also took into account food allergies and environmental
sensitivities. A family history of allergy and migraines was found
to increase the chance of a child's success using dietary intervention. Researchers
looking only at allergy foods or only at additives could miss some
children who would otherwise respond.
"Non-food items that have been implicated are perfumes, fumes,
inhalants..." Breakey addresses the question of why some researchers
find that the removal of allergy foods helps, while others see improvement
from eliminating some additives or natural salicylates. She suggests
that any of these could result in a reduction of the `total body load.'
"By the 1980s recognition of the complexity of the issues
was reflected in methods that investigated more suspect substances
and monitored a wider range of areas of change."
She writes that the improved symptoms noted by parents were sometimes
different from those reported by teachers. "This adds weight
to the concept that parents and teachers monitor different symptoms
and that this difference can add rather than detract from results..." The
many successes Dr. Feingold described were based on the reports from
parents, not from teachers. Critics frequently overlook this, especially
when they cite the very early Harley study at the University of Wisconsin,
where the all ten mothers of preschoolers found the diet to be successful.
"In the past the procedure seemed simple: investigate artificial
colours in hyperactivity, chocolate in migraine, diary foods in asthma
and so on. It has now become clear that such specificity does not
apply and any investigation should include the broad range of presenting
problems and suspect substances."
Joan Breakey is a dietitian/nutritionist in Queensland,
Australia who has studied and written extensively about the effects
of foods and food additives on children. In 1997, the Journal of
Paediatric Child Health (1997, vol.33, 190-194) published
her paper, Review Article, The role of diet and behaviour in
childhood.
Another study, carried out in Australia and published last year, supports the connection between diet and its effect on behavior and learning.
"In 15 children suffering from food induced attention deficit hyperkinetic syndrome, topographic EEG mapping of brain electrical activity was carried out following avoidance and ingestion of previously identified provoking foods....During consumption of provoking foods there was a significant increase in betal activity in the frontotemporal areas of the brain.
"These data support the hypothesis that in a subgroup of children with attention deficit hyperactivity disorder certain foods may not only influence clinical symptoms but may also alter brain electrical activity."
Topographic mapping of brain electrical activity in children with food-induced attention deficit hyperkinetic disorder. Uhlig T, Merkenschlager A, Brandmaier R, Egger J. Institute for Child Health Research, Clinical Sciences Division, West Perth, Australia. Eur J Pediatr 1997 Jul;156(7):557-561.