You kinda just took all the joy out of it, Jon...

Capt. JG wrote:
Just put the bird in... 5 hours to go and counting.... then the tryptophan
kicks in... at least psychologically speaking..

Tryptophan and turkey

According to popular belief, tryptophan in turkey meat causes drowsiness.
Turkey does contain tryptophan, which does have a documented sleep-inducing
effect as it is readily converted into serotonin by the body. However,
tryptophan is effective only when taken on its own as a free amino acid.
Tryptophan in turkey is found as part of a protein, and, in small enough
amounts, this mechanism seems unlikely.

A more-likely hypothesis is that the ingestion of large quantities of food,
such as at a Thanksgiving feast, means that large quantities of both
carbohydrates and branched-chain amino acids are consumed. Like
carbohydrates, branched-chain amino acids require insulin to be transduced
through the myocyte membranes, which, after a large meal, creates a
competition among the amino acids and glucose for insulin, while
simultaneously creating tryptophan's reduced competition with other amino
acids for the Large Neutral Amino Acid Transporter protein for transduction
across the blood-brain barrier.