L-trypophan is not to blame for sleepiness after your Thanksgiving turkey dinner but it is more likely due to the combination of drinking alcohol and overeating which pull the blood away from your brain to help your digestive tract do it's work, and the sugar/insulin effect. Tryptophan, an amino acid and a precursor for serotonin (which aids sleep and anxiety), does not act on the brain unless you take it on an empty stomach with no protein present. Sorry to disappoint you but the levels found in a turkey dinner are far too low to have such an effect.