Biological Bases of the Aggressive Behaviour - Studies on Man

Several recent researchers have shown that aggression increase in man is positively correlated with a decrease in serotonergic tone, as previous researches had shown in non-human primates (increase in intraspecific competition). Neuronal synthesis of serotonin depends on the plasma “trp/Large Neutral Amino Acids” ratio, because of competition made by LNAAs against tryptophan for neuron access, since they use the same carrier to cross the blood-brain barrier. “Trp/LNAAs” ratio value, in turn, tends to be correlated with amino acid composition of the diet: so a low “trp/LNAAs” ratio diet lowers brain serotonin synthesis.Among cereals utilised for human feeding,maize has a very low “trp/LNAAs” value, and this may lead to a brain serotonin deficiency. It has been observed that countries above the median in maize consumption have significantly higher homicide rates than countries below the median.Maize was firstly and largely utilised by Native American peoples. Particularly, Aztecs may constitute a reference pattern of serotonin deficiency due to alimentary causes. Neuro-behavioural after-effects of dietary low “trp/LNAAs” values are thinkable for some African or European peoples, today or in the past.We think that a low dietary “trp/LNAAs” value might constitute a favourable background for the setting of fanatical ideologies, and a risk factor towards violence or intolerance on the occasion of conflicts caused by various motives.