How Metals In Food
Impact Children's Behaviour
The contamination of food with certain metals needs to be urgently
addressed in light of growing evidence linking trace elements to
negative human behaviour, according to a lead researcher in the
Metals and other elements can be present in food either naturally,
as a result of human activities (such as farming, industry or
car exhausts), from contamination during manufacture/processing
and storage, or by direct addition.
It has long been known that excessive amounts of any metal could
be potentially dangerous, but there is now also strong evidence
that some trace elements can contribute to aggressive or anti-social
behaviour, said Neil Ward, professor of chemistry at the UKs
University of Surrey.
Many of the mechanisms are as yet unknown and more case
studies are required, but it is clear that elimination produces
positive improvements, said Professor Ward at a Food and
Behaviour conference held in Brighton, UK, last week.
Some metals and other elements (such as copper, manganese and
zinc) can act as nutrients and are essential for health, while
others (such as arsenic, cadmium, lead and mercury) have no known
beneficial health effects.
Those elements that have no nutritional benefits could not only
be toxic to the system, but they could impede absorption of essential
nutrients in the body, which is particularly problematic in children,
For example, lead has been linked to anti-social behaviour, partly
because it contributes to nutrient depletion.
Lead acts as an anti-nutrient, hindering the utilisation
of magnesium, zinc and vitamin B1. High lead levels have been
linked to a reduction in IQ, negative classroom behaviour ratings
by teachers, juvenile delinquency and increased violent behaviour,
he said, citing studies by Needleman et al., which appeared in
the New England journal of Medicine, JAMA and Neurotoxic Teratology
in 1990, 1996 and 2002 respectively.
Ward, who has studied the relation of trace elements to human
disorders for over 25 years, said aluminium has also been linked
to anti-social behaviour as it competes for the binding sites
of biochemical receptors of other metal ions, such as iron and
zinc. For the same reason, suboptimal dietary intake of zinc or
iron could explain the uptake of aluminium, he said. References
included studies by Moon and Marlow, Wenk and Stemmer, and Birchell
and Chappell, which appeared in Biol Trace Elem Res (1986), Brain
Res (1983) and the Lancet (1988) respectively.
Ward also highlighted findings from one of his own studies, conducted
in 1995, which examined the heavy metal status of incarcerated
young offenders compared to control individuals.
The double-blind case control study used scalp hair and blood
serum tests to determine the levels of zinc, lead, cadmium and
aluminium in the two groups. Levels of lead, cadmium and aluminium
were found to be significantly higher in the young offenders group,
whereas zinc levels were lower.
Zinc deficiency is also thought to occur as a result of ingestion
of certain food colours, and has been linked to hyperactive behaviour
or ADHD in children, said Ward.
The mode of action is not known, but azo dyes have been
linked to behavioural changes in children. These colours could
be acting as chelating agents, which bind available blood zinc
and create a deficiency. The elimination of azo dye beverages
and sweets can have a dramatic effect on some HA or ADHD children,
Food and Behaviour
Professor Ward was addressing an audience of medical professionals,
teachers, healthcare and social workers, and food industry executives
at a conference organised by the charity Food and Behaviour Research
FAB aims to provide research-based information on how nutrition
and diet can affect behaviour, learning and mood. For more information,
click here .