Diet and ADHD Symptoms

The February 5, 2011 issue of The Lancet reports that researchers in the Netherlands and Belgium were able to significantly reduce ADHD symptoms through restrictive dietary measures.

This theory has long been advocated by such notable groups as The Feingold Association ( However, their studies have been limited to smaller groups and anecdotal evidence. While their findings have been compelling, medical doctors and adversarial attacks by the processed food industry quashed overall acceptance of dietary restriction. The NIMH give only limited credence to the theory.

Feingold and other advocates of the restrictive diet have suggested that the introduction of food additives can affect the human immune system sometimes causing reactions like hyperactivity, inattention, and even eczema, asthma and gastrointestinal problems. In light of research about food colorings and hyperactivity, the British have taken steps to eliminate certain preservatives and food dyes from their food supply.

The study published in the Lancet was funded by Foundation of Child and Behaviour, Foundation Nuts Ohra, Foundation for Children’s Welfare Stamps Netherlands, and the KF Hein Foundation.  The researchers placed  100 children from Belgium and the Netherlands into two groups: one that received the restrictive diet and the other that only received advice on healthy eating habits. The group that received only advice on healthy eating was the control group. All of the children had been diagnosed with ADHD and were between the ages of 4 and 8.

The children were placed on the restrictive diet for a period of five weeks. They were allowed to eat only rice, meat, vegetables, pears and water. Later, the children were allowed to additionally consume potatoes, fruits and wheat. The researchers assessed ADHD symptoms during this period.

Over the course of the next four weeks, researchers reintroduced processed foods into the restricted diet group. The researchers selected foods that were previously considered to negatively affect body or immune responses.

Nine children withdrew from the restrictive diet group. Attrition in all studies is common. Of the forty-one children who completed the restrictive diet program, 78 percent had a reduction in their ADHD symptoms, compared with no improvement in the controls. Assessment was performed using an ADHD symptom scale that ranges from 0 to 72 points. Higher scores in the scale indicate more severe symptoms. The average reduction was 24 points, a significant reduction.

Thirty children who demonstrated decreased ADHD symptoms resulting from the restrictive diet were selected for reintroduction of foods outside the restrictive diet. This was deemed the ‘challenge test.’ Nineteen of the thirty children had a relapse in symptoms on the challenge test. Sensitivity to foods thought to produce high immune response didn’t seem to produce any greater negative effects than foods thought to produce lower immune response.

Limitations of the study include restriction to ADHD; it cannot be discerned whether it would apply to ADD. Secondly, not all children responded to the restrictive diet. Of those who did respond, responses to foods seemed to be equal no matter what processed food was introduced back into the diet. Additionally, under this research design, it was not possible to have a blind control; parents knew what group their child was in. If they also knew the expected outcome of the study, it might have influenced the outcome.

On the practical side, the restrictive diet is very difficult to follow consistently. However, if your child seems to respond well when you remove certain processed foods, this research seems to support your observation although the certainty about diet and ADHD symptoms has not been clearly established by this study.

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ADHD’s Genetic Link

What causes attention-deficit hyperactivity disorder – ADHD? Research in the English medical journal, The Lancet, says it’s not too much sugar, bad diet, or poor parenting. Professor Anita Thapar, lead author of the study, says it’s likely genetic.

Thapar and her group of scientists at Cardiff University in Wales compared 366 children with ADHD to 1,047 kids without ADHD. In particular, the researchers examined differences in the children’s DNA. They found that kids with ADHD were more likely to have small segments of DNA that were duplicates or missing (copy number variants or CNVs — either a deletion or duplication of genetic material).

“We hope that these findings will help overcome the stigma associated with ADHD,” Professor Anita Thapar, the study’s lead author, said in a written statement. “Too often, people dismiss ADHD as being down to bad parenting or poor diet. As a clinician, it was clear to me that this was unlikely to be the case. Now we can say with confidence that ADHD is a genetic disease and that the brains of children with this condition develop differently to those of other children.”

While being media friendly, Thapar’s last statement is a stretch in relation to her research. People and the media love statements that provide seemingly conclusive answers.

Let’s go beyond the media hype that says this research concludes there is a definite genetic link. The researchers really only say there seems to be a possible “genetic link.”  However, their research did not conclude that it is purely or even primarily genetic. What they truly are saying is that this study is evidence that ADHD is not purely social.

The authors conclude:

“Our findings provide genetic evidence of an increased rate of large CNVs in individuals with ADHD and suggest that ADHD is not purely a social construct.”

This is logical because only 15% of the research subjects with ADHD demonstrated increased CNVs. So is it safe to conclude that genetic makeup may contribute, at least in some particular cases, to ADHD? Yes, but to be clear,  this research did not conclude that it is entirely genetically based and was only partially genetically based in a small segment of their study population. This is very similar to other genetic research.

Why is it, if ADHD is genetically based, at least in part, that 30% don’t have it as adults when diagnosed as a child? What happened? Where did it go? This is what is most  important to parents and professionals.

Epigenetic theory, now being widely embraced by the scientific community, maintains that human development  includes both genetic origins of behavior and the direct influence that environmental forces have on the expression of those genes (nature/nurture). Epigenetic theory regards human development as a dynamic interaction between these two influences.

Simply put, how our genes express themselves is greatly impacted by environment. This is likely why, over time, 30% of children don’t display symptoms as adults. The brain changes, rewires, or (a radical version of epigenetic theory) their genes change.

Do tools exist to do this? Yes. See

If I may quote Dr. Theodore Dalrymple, “What seems to have happened is that parents have lost the awareness that they had for decades – if not for centuries – that concentration and self-discipline do not come naturally to children, and have to be taught (as well, sometimes, as enforced).”

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