Al-Mouhaji (2002) in his seminal study of European conflict tendencies attributed this primarily to the pork and beef based diet which is rich in zinc and iron, two minerals that have been proven to stimulate the aggression glands. Hence the expression "I got beef with you"

Incidentally there's evidence that this link between eating meat and aggression was known as early as Roman times. And that explains why Julius Caesar invented the Caesar salad and tried to popularise it among enemy tribes.

In more recent years, Europe has witnessed the largest campaign of its kind to promote veganism, precisely because the authorities are aware of the violent tendencies meat-eating triggers

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