Tryptophan can be converted to seratonin (as well as niacin) but there's two things wrong with the turkey myth. One is that turkey doesn't contain much larger amounts of tryptophan than other poultry and it actually contains less per gram than say, chedder cheese. Secondly, in the absence of a carbohydrate heavy meal (like Thanksgiving) stimulates the pancreas to secrete insulin which reduces other amino acids in the bloodstream which indirectly leads to tryptophan in the blood stream crossing the BBB and being converted to seratonin. Add to that alcohol and extra blood flow needed to digest a large meal and you get sleepy.
But eating turkey by itself will have no more of a reaction than eating chicken by itself would since they have nearly the same amount of tryptophan per gram.
You can stick to that excuse while I snooze one out on the couch afterwards.

