Elimination Diet May Improve ADHD Symptoms
Investigators Suggest ‘Diet Therapy” Should Be Considered in All Children With ADHD
February 4, 2011 — In a group of young children with attention-deficit/hyperactivity disorder (ADHD), nearly two-thirds who followed a restricted elimination diet experienced a significant reduction in ADHD symptoms and oppositional defiant behavior. Going off the diet led to relapse.
The findings, from the Impact of Nutrition on Children with ADHD (INCA) study, are published in the February 5 issue of The Lancet.
“We think that dietary intervention should be considered in all children with ADHD, provided parents are willing to follow a diagnostic restricted elimination diet for a 5-week period and provided expert supervision is available,” Lidy M. Pelsser, PhD, of the ADHD Research Centre in Eindhoven, the Netherlands, and colleagues write.
“Children who react favorably to this diet should be diagnosed with food-induced ADHD and should enter a challenge procedure to define which foods each child reacts to and to increase the feasibility and to minimize the burden of the diet,” they advise.
But in comments to Medscape Medical News, Jaswinder Ghuman, MD, of the Division of Child and Adolescent Psychiatry at University of Arizona, Tuscon, author of a linked commentary, said further investigation is needed “to make recommendations for children who are more likely to benefit.”
IgG Measurements Not Helpful
Hypersensitivity or intolerance to foods or food additives is thought to contribute to ADHD. The children in the INCA study were unselected for any food sensitivities, and the researchers found that performing blood tests to identify ADHD “trigger” foods was not helpful. Blood tests assessing IgG levels against foods did not predict which foods might have a deleterious impact on a child’s behavior.
“Total IgE levels were increased in only a few children, equally in (diet) responders and nonresponders, suggesting that the underlying mechanism of food sensitivity in ADHD (which could be related to genetic factors) is nonallergic,” Dr Pelsser and colleagues report.
The INCA study was a 2-phase randomized trial involving 100 children aged 4 to 8 years with ADHD. During a baseline period (weeks 1 to 3), 50 control children continued their normal diet and their parents were given healthy food advice and kept a diary of their child’s behavior. The other 50 children started an open trial with a restricted elimination diet (mainly rice, meat vegetables, pears, and water, complemented with potatoes, fruits, and wheat).
By the end of week 2, 17 of 41 children in the diet group (41.5%) had no behavioral response to the diet, and their diet was further restricted to rice, meat, vegetables, pears, and water.
According to the investigators, by the end of phase 1 (weeks 4-9), symptoms of ADHD and oppositional defiant disorder were significantly improved in 64% of children in the diet group compared with no improvement in controls.
Between baseline and the end of phase 1, the difference between the diet group and the control group in the mean ADHD rating scale (ARS) total score was 23.7 (95% confidence interval [CI], 18.6 – 28.8; P < .0001). The between-group difference in the mean abbreviated Conners’ scale between baseline and phase 1 end was 11.8 (95% CI, 9.2 – 14.5; P < .0001).
Children in the diet group who had a clinical response in phase 1, defined as at least a 40% improvement on ARS score, proceeded to phase 2, a 4-week, double-blind, crossover food challenge, in which high-IgG or low-IgG foods (selected based on individual total IgG levels to 270 different foods) were added to the diet.
After challenges with either high- or low-IgG foods, relapse of ADHD symptoms occurred in 19 of 30 children (63%), regardless of IgG blood test results.
Diet ‘Complex and Challenging’
Dr. Pelsser’s team concludes that a strictly supervised restricted elimination diet “is a valuable instrument to assess whether ADHD is induced by food, [but] the prescription of diets on the basis of IgG blood tests should be discouraged.”
In her commentary, Dr. Ghuman notes restricted elimination diet studies are “complex and challenging.” The INCA study was “well-designed and carefully done, showed a benefit with a supervised elimination diet, and provides an additional treatment option for some young children with ADHD.
“For interested parents,” Dr. Ghuman told Medscape Medical News, “clinicians should encourage them to seek the advice of the child’s primary care provider and a nutritionist for appropriate monitoring of the child’s nutritional status and needs. The parents will need appropriate guidance and supervision for a structured protocol to determine any benefit and identify incriminated foods.”
In her commentary, Dr. Ghuman says it’s important to note that 36% of children either didn’t respond to the elimination diet or didn’t stick to it in phase 1 and 16 children eligible children (and parents) were not motivated to participate in the study.
She also points out that the blinded assessments in the study were based on information provided by parents. However, parents and teachers were aware whether the children were on the elimination diet or not in phase 1.
They also knew that the children entering phase 2 received challenge foods but not whether the foods were high- or low-IgG foods. The beliefs and expectations of the parents and teachers about changes in the ADHD symptoms could have been influenced by this knowledge, Dr. Ghuman notes.
The study was funded by the Foundation of Child and Behaviour, Foundation Nuts Ohra, Foundation for Children’s Welfare stamps Netherlands, and the KF Hein Foundation. Dr. Pelsser is franchiser of the ADHD Research Centre. A complete list of financial disclosures for the other investigators can be found with the original article. Dr. Ghuman has disclosed no relevant financial relationships.
Lancet. 2011;377:446-448, 494-503.