Biomarker Research in ADHD: the Impact of Nutrition part 2 (2ndBRAIN)

Attention Deficit Hyperactivity Disorder (ADHD) is the most prevalent childhood
behavioral disorder with a complex, multifactorial etiology. Current treatment
primarily involves behavioral and pharmacological therapies, although there are
concerns about side effects and long-term efficacy of medication use. Previous
studies have shown promising effects of a few-foods diet (FFD), which led to
significant improvements in ADHD symptoms in 33-64% of children. However,
following an FFD and the subsequent food reintroduction phase requires an
enormous effort of both the child and parents, limiting its applicability as an
approach to treat ADHD. Therefore, the Biomarker Research in ADHD, the Impact
of Nutrition (BRAIN) study conducted in Wageningen in 2018-2020 aimed to
identify the mechanism behind the effect of an FFD on ADHD symptoms and to
identify biomarkers that predict which children will respond to an FFD. In this
study, 63% of participants responded positively an FFD showing a reduction in
ADHD symptoms by at least 40%. This reduction was associated with increased
activation in the precuneus during inhibitory tasks. Changes in ADHD symptoms
after the FFD were also linked to gut microbiome composition. Differences were
also observed in genes related to gut microbial pathways, depending on the
species they were encoded by. The microbiome composition correlated with the
change in precuneus activation after the FFD. Although this study shows
indications that the microbiome-gut-brain (MGB) axis may be involved in the how
an FFD affects ADHD symptoms, the exact mechanism remains unclear. Here, we
propose a second study, 2ndBRAIN, in which we will test the effects of an FFD
in children with ADHD on ADHD symptoms, brain activation and the MGB axis. In
this follow-up study, we will include an control group that will not follow an
FFD but instead receive a daily polyunsaturated fatty acid (PUFA) supplement.
The control group will be used to minimize the possible effects of treatment
expectations of the children and parents. Children with ADHD have significantly
lower plasma and blood concentrations of polyunsaturated fatty acids. Although
a recent Cochrane Review concluded there was little evidence that
polyunsaturated fatty acids supplementation improved symptoms of ADHD in
children and adolescents on average, in children with PUFA deficiencies
supplementation might result in behavioral improvements. By comparing an FFD to
the control we aim to test whether the behavioral, brain, and MGB-axis changes
observed in the BRAIN study are specific to the FFD group and thereby test the
possibility of a causal relationship. Furthermore, a challenge phase will
follow after the FFD and control condition in which all children will consume
their baseline diet again. Including this challenge will allow us to see
whether behavioral, MGB and brain changes persist after returning to the
baseline diet. We hypothesize that, on average, the FFD group will show
improvements in ADHD symptoms, and changes in brain activation (increased
inhibition-related precuneus activation in responders) and MGB functioning
after following the FFD. We hypothesize that after the challenge phase, these
changes will have gone back to baseline. Furthermore, in the control group we
hypothesize that the ADHD symptoms, MGB functioning and brain activation on
average remain relatively stable over time.

We aim to examine the effects of an FFD on ADHD symptoms, inhibition-related
brain responses and taxonomic composition and functional capacity of the gut
microbiota.

Open-label randomized control trial with researchers blinded during sample
processing and initial data analyses.

In the FFD group, after a 2-week baseline period (regular diet), participants
will follow a 5-week FFD preceded by a 1-week transition period followed by a
(maximum) 3-week challenge phase preceded by a 1-week transition period. In the
control group, after the 2-week baseline period participants are instructed to
take daily PUFA supplements and to eat their diet as usual during 5 weeks,
followed by a three-week challenge phase preceded by a 1-week transition
period.

This type of paradigm poses no significant risk. From the baseline period until
the last measurement (12 weeks) parents will record food intake, daily
activities and behavior of the child. The child will record stool frequency and
type. During the screening (T0) the child will be examined by a pediatrician
who will confirm the ADHD diagnosis or make a research diagnosis and perform a
physical examination. If included in the study children will have a mock-fMRI
session (15 min). On the three measurement days (before start FFD or control
period (T1), at the end of FFD or control period (T2) and after the challenge
period (T3)) blood (15 ml) and saliva will be collected from the children after
an overnight fast, and stool and urine samples will be self-collected.
Furthermore, children will have a 30 min fMRI scan and perform a 5 min
cognitive task. Parents will complete questionnaires about the child*s physical
symptoms and behavior. Children in the intervention group will be asked to
follow a five-week FFD while children in the control group will be asked to
take daily PUFA supplements and continue their diet as usual during 5 weeks.
After following the FFD or control period, both groups will be asked to adhere
to their baseline diet until the last measurement. Parents can contact the
examiners as soon as their child*s behavioral symptoms reappear during the
challenge phase to schedule the final measurement as soon as possible. For the
FFD group, adhering to the FFD can be considered challenging, but may also
reduce ADHD symptoms. Additionally, all participants will invest time in
several measurements and sample collections. Because of the previous findings
that an FFD can ameliorate behavior in significant proportion of children with
ADHD (Nigg et al., 2012; Pelsser et al., 2011; Hontelez et al., 2021), this
study can be considered therapeutic.