Food and Behaviour Research

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11 Feb 2011 - Nutraingredients - 'Restricted diet' linked to reduction in ADHD: Study

by Nathan Gray

FAB RESEARCH COMMENT:

Results of this randomised controlled trial indicate that ADHD symptoms in many children may be reduced by dietary modifications - specifically, the elimination of all processed foods and drinks, as well as some other foods that are common triggers for food allergies or intolerances. 

As usual, reactions to the publicaton of this study have varied considerably (see 'ADHD Diet Plan gets mixed reviews'). The fact that the parents, children and others involved could not be fully 'blinded' to the dietary intervention is enough for some commentators to dismiss the entire study - although this is almost impossible to achieve in studies of real diets in free-living individuals. 

The study authors themselves accept that some of the improvements found may have reflected parental expectations - or the structured attention paid to the children given the exclusion diets.  Whatever the reasons, significant improvements were seen in no less than 64% of ADHD children (63% of whom relapsed on the re-introduction of excluded foods).

This suggests that there could be significant benefits (for a variety of reasons) if parents were encouraged simply to provide more structured diets for their ADHD children, excluding highly processed foods and drinks (which often have little or no nutritional value in any case). This would also be likely to benefit their general health.

For further details of the study reported here, see

A restrictive diet, which bans processed foods, may reduce the symptoms of attention-deficit hyperactivity disorder (ADHD) in young children, according to a new study.

New research published in The Lancet, suggests that a diet restricted to just a few basic ingredients could be “a valuable instrument to assess whether ADHD is induced by food.” In the new study, children with ADHD were put on a ‘restricted elimination diet’ – containing only rice, meat, vegetables, pears and water – for five weeks. The authors found that ADHD symptoms were reduced in 78 per cent of children placed on the diet.

“A strictly supervised restricted elimination diet is a valuable instrument to assess whether ADHD is induced by food,” wrote the researchers, led by senior author Professor Jan Buitelaar from Radboud University, The Netherlands.

“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 five-week period, and provided expert supervision is available,” they said.

However, writing in an accompanying comment piece for The Lancet, Dr Jaswinder Ghuman from the University of Arizona said that in her opinion, the diet should not be continued for more than five weeks, “because long-term effects of dietary elimination on the child's nutritional status are not known.”

ADHD development

The authors said that several genetic and environmental factors are involved in the development of ADHD. One of the many environmental factors proposed to have an effect on ADHD development is diet.

According to the National Institute of Mental Health (NIMH), parents have long suspected that sugary foods, additives, and colours, may play a role in inducing symptoms, however there is very little evidence to support such theories.

Prof. Buitelaar and colleagues noted that some children have negative physical reactions to certain foods, and suggested that foods may also affect the brain in ways that result in changes in behaviour.

They explained that ADHD may be triggered by a hypersensitivity reaction to certain foods, adding that some complementary medicine practices test for the antibody IgG (immunoglobulin G) and recommend eliminating foods high in IgG for ADHD. However, they noted that IgG testing is unproven to work, and remains controversial among mainstream physicians.

Study details

The new research investigated the link between ADHD and diet by recruiting 100 children diagnosed with ADHD (between the ages of 4 and 8), and putting them on a restricted food (hypoallergenic) diet. After this a ‘food challenge’ was given to the children to test whether foods high in IgG re-triggered ADHD symptoms.

Of the children to complete the restrictive diet phase of the trial, 78 percent had reduced ADHD symptoms, compared with no improvement in the controls.

After five weeks, children on the restricted diet received food challenge diets, in which certain foods (either high or low in IgG) were re-introduced into the diet.

Buitelaar and co workers reported “a substantial relapse in behaviour in 63 per cent of children” when previously restricted processed foods were put back in the diet. However they said that no differences in relapse or behavioural effects were seen between high- and low- IgG foods.

Commenting on the study Dr Ghuman said: “IgG levels against foods did not predict which foods might lead to a negative effect on behaviour because an equal number of low and high IgG food challenges resulted in relapse of ADHD symptoms.”

Unanswered questions

Ghuman warned that the new study does not answer a number of questions, such as whether or not the elimination diet reduces symptoms long-term, and said that clinical practice should not be changed based on the results of one study.

The authors also noted that the study had potential limitations, due to the fact that it was open-label.

“Expectations of the parents cannot be fully ruled out as a possible cause of the behavioural improvements … We (also) cannot rule out that the behavioural improvements during the first phase might have been caused by increased attention for the child in the diet group,” they said.

Source: The Lancet
Volume 377, Issue 9764 , Pages 494-503, doi: 10.1016/S0140-6736(10)62227-1
“Effects of a restricted elimination diet on the behaviour of children with attention-deficit hyperactivity disorder (INCA study): a randomised controlled trial”
Authors: L. Pelsser, K. Frankena, J. Toorman, H.F. Savelkoul, A.E. Dubois, R.R. Pereira, et al

Source: The Lancet
Volume 377, Issue 9764 , Pages 446-448, doi: 10.1016/S0140-6736(11)60133-5“Restricted elimination diet for ADHD: the INCA study” Author: J.K. Ghuman