In the TRACE study, we examine the short (after 5 weeks) and long term (after 1 year) effects of two dietary treatments for children with ADHD (5-12 years old). In addition, we examine the underlying biological mechanisms of these dietary treatments by collecting blood, saliva and stool samples and performing a fMRI. We examine the effects of an elimination diet and a healthy, balanced diet based on the WHO guidelines. We will compare the two dietary groups with a group of children receiving care-as-usual (e.g. medication, psycho-education). Primary outcomes include for instance ADHD symptoms, emotion regulation problems and cognitive functioning. We will include 81 children in each dietary group and 60 children in the care-as-usual group.