Childhood ADHD and Food "Sensitivity"

I admit that I am a skeptic about the effect of diet on ADHD and most mental disorders.  No one can argue that a healthy diet should not be routinely advised for all individuals with or without an emotional disorder.   However, I am open to looking at research studies and data--I'm willing to change my opinion if the research supports such a change.

A group of Dutch researchers recently published a study of diet and ADHD symptoms in a small sample of children with ADHD between the ages of 4 and 8 years. This study was published in Lancet, a highly regarded scientific journal.  In the study one hundred children were assigned to an experimental group (elimination diet) or a control group (healthy diet education).  ADHD as well as oppositional defiant symptoms were monitored during the experimental phase by a single pediatrician (blinded to diet assignment), parents (not blinded to assignment) and teachers (not blinded to assignment).  The authors noted that it was impossible to blind parents and teachers due to the food restrictions required in the elimination diet group.

The elimination diet was a diet called few foods diet: rice, meat, vegetables and pears.  Strangely, parents were allowed to add potatoes, fruits and "wheats".  If there was no improvement after two weeks of this modified few foods diet, the diet was then restricted to the rice, meat, vegetables and pears diet.  Here were the key findings reported in the study:

• 32 of 41 (78%) children on the elimination diet had at least a 40% reduction in the ADHD Rating Scale (defined as response)--I was unable to find the response rate in the education group although the mean rating on this measure did not change pre- to post
• Improvement was noted by both parents and teachers on ADHD rating scales
• Ratings of severity of oppositional defiant disorder also improved along with ADHD symptoms
• After the initial phase, ADHD responders to the elimination diet were re-challenged with food and the majority (63%) "relapsed" when re-challenged with non-elimination diet foods.  This occurred in those re-challenged with either foods considered high or low risk for sensitivity based on individualized food-specific immune globulin G assays.

There are several things of note about this study.  First, this team previously reported a similar finding in a smaller sample--so this is not an independent replication. Second, the primary outcome ratings in the study were made by a single pediatrician that was "masked".  I would have liked to have seen consistent results from several blinded raters.  Additionally, the pediatrician ADHD ratings were scheduled at nine weeks in the elimination diet sample and 13 weeks in the control sample so this had the potential to void blinding in some cases.  The parents were not blinded to intervention but were instructed to not reveal their diet assignment to the pediatrician.  The fidelity of this instruction is not addressed.

One other issue here is biological plausibility.  The authors propose a food sensitivity mechanism-- not a distinct food allergy mechanism.  Serum IgE levels can be markers of allergy to food and non-food antigens.  The elimination diet "responders" did not have higher rates of elevated IgE compared to the non-responders. Exactly how a non-allergic food sensitivity could cause persistent attention, motor and behavior problems is unclear to me. 

I was surprised this study was published in a top-notch research journal.  Maybe it will be replicated by an independent group using a better design.  I wouldn't hold my breath on this or make treatment decisions based on the results of this small study.

I guess if I had a child with severe ADHD, I would not make a dietary change based on this study.  I would continue evidence-based treatments and continue to keep abreast of research advances in the diagnosis and treatment of this disorder.


Photo of African Lion Courtesy of Sarah Yates

Pelsser, L., Frankena, K., Toorman, J., Savelkoul, H., Dubois, A., Pereira, R., Haagen, T., Rommelse, N., & Buitelaar, J. (2011). Effects of a restricted elimination diet on the behaviour of children with attention-deficit hyperactivity disorder (INCA study): a randomised controlled trial The Lancet, 377 (9764), 494-503 DOI: 10.1016/S0140-6736(10)62227-1