It's irrelevant whether you like turkey or not because someone is going to be handing you a plate of it very soon. And after the meal, there's a good chance that you'll get sleepy. But will the cause of your drowsiness be the turkey, the booze, or your brother-in-law's tedious commentary about his golf game?
tryptophan
The perils of Thanksgiving! Hellish traffic, Aunt Gertrude's bunions, and a whole bunch of toxic chemicals. We are all doomed.
There is a naturally-occurring chemical called skatole. Its claim to fame is that it is named after, and smells like, fecal matter. It's "synthetic" but also "man-made" and there's a revolting distinction in this case. It's also an additive used in cigarettes and strawberry ice cream (??). Do your "duty" and read this article.