“Eating turkey makes you sleepy.”

The idea that eating turkey leads to irresistible drowsiness is a widely held belief, particularly around holidays like Thanksgiving. This common misconception largely stems from the fact that turkey contains tryptophan, an essential amino acid. In the 1970s, some non-specialist doctors and popular health columns began to link tryptophan in turkey to sleepiness, despite a lack of rigorous scientific backing at the time. The myth gained further traction and became a popular "factoid" repeated in media, even being popularized by an episode of "Seinfeld" in the 1990s, solidifying its place in popular culture.

While it is true that tryptophan serves as a precursor to serotonin, a neurotransmitter that helps regulate mood, and then melatonin, a hormone that promotes sleep, the amount present in a typical serving of turkey is simply not enough to induce a "food coma." In fact, turkey does not contain significantly more tryptophan than many other common protein-rich foods like chicken, beef, nuts, or cheese. For dietary tryptophan to have a measurable effect on sleepiness, it would require a much larger dose, typically found in supplements of several grams, far exceeding what one would consume in a meal.

The feeling of sleepiness often experienced after a large meal, especially a holiday feast, is more likely attributed to several other factors. Consuming a large, heavy meal, particularly one rich in carbohydrates and fats, causes the body to divert significant blood flow to the digestive system, which can reduce blood flow to the brain and lead to lethargy. High carbohydrate intake triggers a release of insulin, which helps remove most amino acids from the bloodstream, allowing tryptophan to more easily cross the blood-brain barrier. However, it's the sheer volume of food, the "sugar crash" from rapidly digested carbohydrates, and often the consumption of alcohol that are the primary culprits behind post-meal drowsiness, rather than the tryptophan in turkey.