People often think that eating turkey makes them sleepy. Traditionally, the cause has been blamed on the amino acid, tryptophan, which is found in turkey. One of the functions of tryptophan is to act as a chemical precursor to the synthesis in the body of serotonin. Serotonin affects our mood and helps us have happy thoughts, but it also can be converted to melatonin. Melatonin is a hormone that functions in several ways, one of which is to regulate our sleep-wake cycles. A result of increased melatonin is sleepiness.
But, having said that, the turkey and its low amount of tryptophan is probably not what is making you sleepy: Tryptophan doesn’t act on the brain unless it is taken on an empty stomach with no protein present. If you consider that a turkey is mostly all protein and most people don’t really have an “empty stomach” during Thanksgiving dinner – then the turkey appears to be wrongly accused.
The amount of tryptophan eaten during a holiday meal is generally too small to have an appreciable effect. That lazy, lethargic feeling so many are overcome by at the conclusion of a festive meal is most likely due to overeating, having too many foods with simple carbohydrates in them that metabolize very quickly into the blood stream and increase the blood glucose levels. This along with a holiday cocktail will deplete you of all your energy causing you to feel sluggish and tired. You can find similar levels of tryptophan in beef, pork and lamb. Eggs and cheese have higher levels of tryptophan than turkey or these other meats, and these and other foods like them are not associated with making us sleepy.