For example, here is a new British and American study conducted in part by the NIH that has shown that to a startlingly high degree, not only is violent behavior correlated to a poor diet but also that by improving the diet with supplements can reduce and even eliminate violent, anti-social tendencies in prisoner populations. They have found that one of the key supplements to be Omega-3 essential fatty acids.
Robert Rose may be on to something, but I'd need to see more to be convinced that there's enough cause and effect to matter. I don't include fish oil in my diet, and I don't go around hurting people.
To be fair, I'd have to read the whole study, which I haven't done, and understand it, which is probably beyond me. I can absolutely buy that diet has an effect on behavior--that makes intuitive sense. But only one of many.
Still, all in all, this is interesting.