Tryptophan & Carbohydrate Chemistry
The turkey is often cited as the culprit in afterdinner lethargy, but the truth is that you could omit the bird altogether and still feel the effects of the feast. Turkey does contain L-tryptophan, an essential amino acid with a documented sleep inducing effect.
L-tryptophan is used in the body to produce the B-vitamin, niacin. Tryptophan also can be metabolized into serotonin and melatonin, neurotransmitters that exert a calming effect and regulates sleep. However, L-tryptophan needs to be taken on an empty stomach and without any other amino acids or protein in order to make you drowsy. There’s lots of protein in a serving of turkey and it’s probably not the only food on the table.
It’s worth noting that other foods contain as much or more tryptophan than turkey (0.333 g of tryptophan per 100 gram edible portion), including chicken (0.292 g of tryptophan per 100 gram edible portion), pork, and cheese. As with turkey, other amino acids are present in these foods besides tryptophan, so they don’t make you sleepy.
So, why are you sleepy after a big turkey dinner? It’s a combination of the type of food, amount of food, and celebratory atmosphere. Happy Thanksgiving!