In new research published in this week’s Lancet, researchers conclude that a special restricted diet (the restricted elimination diet) should be part of the standard of care for all children with attention-deficit hyperactivity disorder (ADHD). The Article is by Professor Jan Buitelaar, Radboud University Nijmegen Medical Centre, Netherlands, and Dr Lidy M Pelsser, ADHD Research Centre, Eindhoven, Netherlands, and colleagues.
From previous work, the authors have postulated that ADHD might be an allergic or non-allergic hypersensitivity disorder in some children, triggered by any types of food that can cause allergic reactions. In this new study children aged 4 to 8 years and diagnosed with ADHD took part in this randomised controlled trial, in which 50 were given the elimination diet and the other 50 (controls) given instructions for a general healthy diet for five weeks. Thereafter, diet group children reacting favourably to the restricted diet were assigned to a second phase in which two different groups of foods, one after the other, were added to the elimination diet. One food group contained foods that induced high levels of immunoglobulin G (IgG) in their blood (high IgG food), while the other group contained low IgG foods. The food groups were different for each child, based on each child’s blood results. The purpose of this phase was to investigate whether IgG blood tests are useful to identify foods that trigger ADHD.
The researchers found that in the first part of the study, children in the intervention group showed significant improvements in their ADHD symptoms, as demonstrated by the ADHD rating scale. The oppositional defiant disorder symptoms, also present in half the children, also decreased.
The authors point out that while previous studies have shown a connection between food and ADHD, the cohorts in these trials were small or included only children known to have an allergic constitution, preventing the results being applicable to the general population. They say: “Our study shows comparable effect sizes in patients who are representative of the general ADHD population, supporting the implementation of a dietary intervention in the standard of care for all children with ADHD.” They add: “The prescription of diets on the basis of IgG blood tests should be discouraged.”
They say: “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. Children who react favourably 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 minimise the burden of the diet. In children who do not show behavioural improvements after following the diet, standard treatments such as drugs, behavioural treatments, or both should be considered.”
In a linked Comment, Dr Jaswinder Kaur Ghuman, Department of Child and Adolescent Psychiatry, University of Arizona, Tucson, Arizona, USA, says that an elimination diet trial should be implemented only under the supervision of the child’s primary health-care provider and a nutritionist to ensure that growing children do not suffer from nutritional deficiencies with the restricted diet. She concludes: “Diagnosing food sensitivity is complex, can take several weeks, and can be burdensome for families to implement. The restricted diet can be tried for 2-5 weeks. If there is benefit, the restricted foods can be added back weekly, one food component at a time, to identify the problem foods to be excluded from a less restrictive permanent diet. In my opinion, a stringent elimination diet should not continue for more than 5 weeks without obvious benefit because of the time, effort, and resources required implementing the restricted diet and because long-term effects of dietary elimination on the child’s nutritional status are not known.”