Food and Behaviour Research

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3 Nov 2011 - The Telegraph - Could zinc help prevent autism?

by Stephen Adams, Medical Correspondent

Both the headline of this article and the reported comments from the researchers suggest a causal link between zinc deficiency and autism, despite the fact that the data collected for this study could - at best - only show an association between the two.

FAB RESEARCH COMMENT:

Both the headline of this article and the reported comments from the researchers suggest a causal link between zinc deficiency and autism, despite the fact that the data collected for this study could - at best - only show an association between the two.

As the comments from independent researchers point out, this study did not even involve a matched control group - relying instead on comparing the zinc status (as assessed from hair samples) of a sample of autistic children aged 0-3 years with the levels expected in the general population.

The central finding was that over half of the autistic children were zinc deficient on this measure. (The reliability of hair samples as indicators of zinc status is another issue).

As one of the independent commentators points out, even if zinc levels were unusually low in autistic compared with normally developing children, this could simply reflect poorer dietary intakes in the autistic children, rather than being a cause of their difficulties.

Further research would be needed to investigate these various possibilties.  

Nonetheless, given the importance of zinc to general health as well as brain function, overt zinc deficiency in any child would provide grounds for dietary assessment and intervention to improve this (and any other deficiencies in essential nutrients).

For more details of this research, see

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Japanese researchers who took hair samples from nearly 2,000 diagnosed autistic children, aged from birth to three, found almost half of them had a zinc deficiency.

The team, from the La Belle Vie Research Laboratory in Tokyo, concluded that zinc deficiency could lead to autism.

They wrote in the journal Scientific Reports: "These findings suggest that infantile zinc deficiency may epigenetically contribute to the pathogenesis of autism and nutritional approach may yield a novel hope for its treatment and prevention."

In their research, three-quarters of the children from whom samples were taken were male and a quarter female. This was not unrepresentative, as autistic spectrum disorders - the umbrella term for all types of autism - are known to affect boys more than girls.

However, scientists have attacked the study for jumping to conclusions, by failing to compare zinc concentrations with those in children without autism.

Uta Frith, emeritus professor of cognitive development at University College London, said:

"To draw conclusions from this study we would need to see data about the levels of zinc in children who do not develop autism spectrum disorders at different ages.

"Without this information we cannot say whether zinc deficiency is associated with development of autism spectrum disorders, let alone whether it is a contributory cause."

Dorothy Bishop, professor of developmental neuropsychology at Oxford University, said:

"This study is problematic because the researchers assessed zinc levels only in an autistic group, relying on existing datasets to provide the data on expected normal ranges for zinc in children.

"To be convincing they should have compared zinc levels in hair of children with autism with levels for a control group matched in age and environmental background, with the measures being made by researchers who were unaware of the child's group.

"Furthermore, if zinc deficiency is confirmed in future research, then it remains unclear whether this is a cause of autism, or rather reflective of dietary abnormalities.

"Many children with autism will eat only a restricted range of foods, and some have a habit of chewing inedible objects."