Here's the lowdown: turkey contains the amino acid L-tryptophan, which produces sleep-promoting serotonin and melatonin. But turkey has about the same amount of tryptophan as other meats. It may even have a built-in secret weapon against sleepiness: an abundance of protein, which can regulate insulin levels and actually combat fatigue. So don't blame the turkey for your tiredness; the heavy load of carbs that made up the rest of the meal are likely the culprits. Here's what turkey really does to your body.