Early nutrient deficiency may increase adolescent violence
aggressive behaviour throughout childhood and late adolescence,
report US researchers.
Their study, thought to be the first to show that deficiency in nutrients like iron, protein and B vitamins in infancy can cause behaviour problems right up until the end of teenage years, adds to the evidence showing the value of healthy diets for children.
It suggests that diet play a role in preventing antisocial behaviour.
"Identifying the early risk factors for this behaviour in childhood and adolescence is an important first step for developing successful prevention programs for adult violence," explained the lead author of the study, Jianghong Liu, a postdoctoral fellow with the University of South California's Social Science Research Institute.
Writing in this month's issue of the American Journal of Psychiatry (161:2005-2013), the authors describe following the nutritional, behavioural and cognitive development of more than 1,000 children living on Mauritius over a 14-year period. The sample included children with Indian, Creole, Chinese, English and French ethnicities.
Researchers assessed their nutrition at age three, looking particularly at conditions that would reflect deficiency of the B vitamin riboflavin, protein, zinc and iron.
The children's intelligence level and cognitive ability were also tested, and follow-up at ages eight, 11 and 17 years involving interviews with parents and teachers to examine how the children were behaving in school and at home.
Over time, a link became evident between malnourishment and antisocial or aggressive behaviour, said study co-author Adrian Raine.
Compared to those in the control group, the malnourished children showed a 41 per cent increase in aggression at age eight, a 10 per cent increase in aggression and delinquency at age 11 and a 51 per cent increase in violent and antisocial behaviour at age 17.
While social class did not play a significant factor in behaviour, intelligence level did, Raine said.
"Poor nutrition, characterized by zinc, iron, vitamin B and protein deficiencies, leads to low IQ, which leads to later antisocial behaviour," he said. "These are all nutrients linked to brain development."
Researchers also found that the more indicators of malnutrition there were, the greater the antisocial behaviour.
The implications of the findings are significant when the levels of iron deficiency in many populations are taken into account. Iron deficiency is the UK's most common nutritional disorder. In the US, 7 per cent of toddlers suffer from iron deficiency, a number that jumps to between 9 per cent and 16 per cent in adolescent and female groups.
Iron deficiency is between 19-22 per cent in black and Mexican American females, he said.
"This is a problem in America. It's not just a problem in the far-away Indian Ocean," Raine said. "If it's causal, there's an intervention implication there. At a societal level, should parents be thinking more about what kids are eating?"
The study also suggests that antisocial behaviour may be preventable.
"There's more to antisocial behavior than nutrition, but we argue that it is an important missing link," Raine said. "Biology is not destiny. We can change the biological disposition to antisocial and aggressive behaviour."
