Amino acids are the building blocks of proteins. Some cannot be synthesized by our bodies and are therefore considered “essential” – they must be obtained from one’s diet. Tryptophan, an essential amino acid found in eggs, meats, chocolate, dairy, etc., regulates nitrogen balance. It’s also the precursor for the neurotransmitter serotonin (5-hydroxytryptamine), which, in turn, gets converted into melatonin – a crucial sleep-wake cycle hormone.
The tryptophan found in turkey is comparable to that of other poultry; however, carbohydrate consumption during Thanksgiving dinner (or any meal) is implicated in post-prandial somnolence.
A huge carb load triggers insulin release causing glucose and large, neutral branched-chain amino acids like valine and leucine to shift intracellularly. Now, there’s an excess of tryptophan left in the plasma. Because of less competition from other amino acids, which were shifted intracellularly, more tryptophan can cross the blood-brain barrier via amino acid transporters into the central nervous system to generate serotonin (raphe nuclei) and melatonin in the pineal gland.
Furthermore, to digest such large amounts of food, significant shunting of blood from the peripheral musculoskeletal beds to the digestive tract coupled with parasympathetic activation (“rest and digest”) confers sleepiness.
I hope you all have a happy Thanksgiving… and a wonderful nap afterward! 😃