Many people believe that eating turkey makes them feel sleepy, especially after Thanksgiving dinner. However, the truth is more complicated than that. Turkey contains an amino acid called tryptophan, which can contribute to the production of serotonin and melatonin, hormones that can promote relaxation and sleep. However, tryptophan alone is not enough to make you feel sleepy. Eating foods with tryptophan in addition to a large number of carbohydrates leads to sleepiness. Carbohydrates come from the other typical foods at the Thanksgiving table, such as bread, potatoes, peas, corn, sugary drinks, and desserts.

Overeating and consuming high-carbohydrate, high-fat meals can also lead to post-meal sleepiness, with peak fatigue happening an hour to an hour and a half after you finish eating. Blood flow is redirected to the stomach to aid digestion, which can cause less blood to be available in the brain, leading to feelings of drowsiness.

In summary, while turkey does contain tryptophan, it is not the sole cause of post-Thanksgiving sleepiness. Eating a large meal with a lot of carbohydrates and fats, overeating, and changes in metabolic activity during digestion can all contribute to feelings of drowsiness.