In this study, researchers followed 1,000 children living in Mauritius (an Indian ocean island near the coast of Africa) for 14 years, monitoring their nutritional intake and behavioral and cognitive development. At the age of three, they looked for four specific indicators of malnutrition: anemia (iron deficiency), sparse (thin hair caused by protein deficiency), angular stomatitis (cracking of lips through shortage of B vitamin), and hair dyspigmentation (protein deficiency causing the change of hair color to reddish-orange).
At ages 8, 11, and 17, researchers took account on to how the children behaved in school and at home. Overtime, in comparison to those in controlled groups (those that did not suffer from malnutrition), these malnourished children demonstrated a 41% increase in aggression at 8, a 10% increase age 11, and as much as 51% increase in belligerence and antisocial behavior at age 17. With the results of this study, a conclusion was drawn that malnutrition in vitamin B, iron, zinc, and protein leads to lower IQ, which in turn leads to violent antisocial behavior such as lying, cheating, stealing, drug use, and property destruction. In addition, researchers also found that the more indicators of malnutrition there were, the greater the aggressive behavior.
True that nutritional deficiency may be the cause of aggressive - antisocial behavior. However, there are also many other factors that need to be taken into consideration. Social class, parents, peers, environment, and their own temperament all play major roles in adolescences' behavior. They are important factors - much more significant that poor nutrition alone. If this is entirely accountable, does it mean that children in third world countries are and will grow up to be the most aggressive and antisocial? Surely not. And how do you explain children that were fed and brought up well that turned into criminals? While I believe that nutritional deficiency may have effects in 'bad' behavior, the influence is very very acute.