Another list has carried the following information:

"A Dutch study published in the November, 2002 issue of 
Brain, Behavior and Immunity (the official journal of the 
PsychoNeuroImmunology Research Society), found that 
tryptophan worked directly on the brain to alter cognitive 
functioning and produce mood swings and depression in 
human subjects. ... turkey protein contains an excess of this amino 
acid."

So do certain cheeses, such as parmesan and mozzarella, according to the same post.

Anyone in a position to comment on this Dutch study?

Evelyn