According to Wageningen University researchers, the effect of poly-unsaturated fatty acid (PUFA) supplementation is unlikely to provide a ‘tangible contribution’ to ADHD management.
“The PUFA Effect Sizes (ESs) are small to negligible, warranting the conclusion that as yet PUFA supplementation should not be advised as a treatment of ADHD,” the study recommended.
“However, it should be acknowledged that the individual effect of an intervention may be different from the average group effect."
The team also highlighted the need for further research into the gut flora as an environment that responds rapidly to a change of diet, opening up possibilities for probiotic intervention.
“Further research may offer novel diagnostic and treatment possibilities, for example specific probiotics for children with ADHD,” the researchers said.
The potential efficacy of probiotics in managing neurologic diseases is an area of great interest, as one recent study has shown.
However, formulation, dosage and timing are factors that need to be looked at to determine optimal regimen for each neurological disorder and the populations that would benefit.
In addition, the tolerability and safety of probiotics in patients with neurologic conditions would be of upmost priority.
The gut flora has been shown to produce neurochemicals similar to those produced by the brain.
The mimicking of the brain’s activities by the gut microbiota also opens up further research into the bi-directional communication of the gut-brain axis that may play a role in the onset of certain psychiatric disorders.
Further gut-brain signalling research has shown the microbiota and its microbiome as influencing brain development and behaviour.
“Establishing the biological basis of environmental influences on psychiatric disorders, including research into neuroendocrine mechanisms, is important to define ‘how environments get under the skin,” the study explained.
“Differences in neurotransmitters or in microbiota composition could provide an explanation for individual differences in diet response.”
Previous fish oil findings
The findings are somewhat unexpected as the use of PUFA as a dietary intervention to manage neurological disorders has been met with a certain degree of success, as one review has concluded.
In addition, another review provided evidence for a small effect noticed by supplementing the diet with free omega-3 fatty acids, such as eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
Omega-6 free fatty acids were also scrutinised and included linoleic acid (LA) and arachidonic acid (AA) in the treatment of ADHD.
Commenting on the study’s findings, Harry Rice, vice-president of Regulatory & Scientific Affairs at the Global Organisation for EPA and DHA Omega-3s (GOED) said: “The reality is that for omega-3s (EPA/DHA) and ADHD, there's limited rigorous data upon which to draw conclusions.”
“But there is encouraging data suggesting that children with the lowest omega-3 baselines are the ones that benefit the most from omega-3 supplementation. Investigators recruiting for future studies should recruit children with low baseline omega-3 levels.”
The review’s findings also echo the International Society for Nutritional Psychiatry Research’s stance that mentioned the ‘emerging and compelling evidence for nutrition as a crucial factor’ in mental disorders, and that ‘consideration of nutrition should be part of standard practice.’
“I am in full agreement with this as it applies to omega-3s and omega-6s,” added Rice. “We've known for years that people get too little omega-3s (EPA/DHA) and too much omega-6s.
“For many health conditions, not just mental disorders, there's sufficient evidence to demonstrate that those afflicted with certain conditions have blood levels ‘low’ in omega-3s and ‘high’ in omega-6s.
“This does not mean that all omega-6s are bad. Rather, a healthier balance is needed (more omega-3s and less omega-6s). Not that there is an optimal ratio.”
A literature search resulted in 14 meta-analyses studies. Six of which were focused on artificial food colour (AFC) elimination, a few-foods diet (FFD) approach consisting of lamb, chicken, potatoes, rice, banana, apple and brassica and PUFA supplementation.
All children were diagnosed with ADHD and chosen studies also included the elimination of one food component (sugar or AFC), food groups (major allergens/gluten/high histamine) or additives (FFD).
Along with the findings,the researchers attempted to move the discussion beyond the question of whether a FFD may affect ADHD towards the question how food exerted its effect and in which children.
This included nailing down the biological basis of environmental influences on psychiatric disorders, including research into neuroendocrine mechanisms.
“Further research may result in finding alterations in metabolites that are regulated by the gut flora, differences in neurotransmitters or in microbiota composition,” the study concluded.
Source: PLOS One
Published online ahead of print: doi.org/10.1371/journal.pone.0169277
“Diet and ADHD, Reviewing the Evidence: A Systematic Review of Meta-Analyses of Double-Blind Placebo-Controlled Trials Evaluating the Efficacy of Diet Interventions on the Behavior of Children with ADHD.”
Authors: Lidy Pelsser, Klaas Frankena, Jan Toorman, Rob Rodrigues Pereira