At age 8, teachers gave feedback about whether the subjects were acting out in school with behavior ranging from irritability to picking fights with other children.
At age 11, the feedback came from parents who told researchers about whether their children lied, cheated, got into fights, bullied others, destroyed property or used obscene language.
At age 17, both parents and teachers reported on antisocial behavior such as stealing, drug use, destroying property or being deliberately cruel to others.
Over time, a link became evident between malnourishment and antisocial or aggressive behavior, said Adrian Raine, a co-author of the study and holder of the Robert Grandford Wright Professorship in Psychology in USC's College of Letters, Arts and Sciences.
Compared to those in the control group the group that did not suffer from nutritional deficiencies malnourished children showed a 41 percent increase in aggression at age 8, a 10 percent increase in aggression and delinquency at age 11 and a 51 percent increase in violent and antisocial behavior at age 17.
While social class did not play a significant factor in behavior, 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 behavior," 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 behavior.
The findings have implications for the United States, Raine said, where 7 percent of toddlers suffer from iron deficiency, a number that jumps to between 9 percent and 16 percent in adolescent and female groups.
Iron deficiency is between 19 percent and 22 percent 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 i
Contact: Usha Sutliff
University of Southern California