Wikipedia says "Turkey is high in tryptophan, and is commonly credited with causing sleepiness after a meal, however this is largely a misconception. Turkey dinners are commonly large meals served with carbohydrates, fats, and alcohol in a relaxed atmosphere, all of which are bigger contributors to post-meal sleepiness than the tryptophan in turkey." and links that to a report from the Massachusettes Institute of Technology. I dunno though, because turkey makes me damn sleepy.