Thanksgiving dinner. Ms Jones, CC2.0 license
The tryptophan in turkey is often thought to cause post-holiday drowsiness. This is not true, though the meal does have something to do with it.
Turkey, like many other foods, contains protein. When protein is eaten, the body breaks it down into its components, called amino acids. Tryptophan is one of the amino acids in turkey. One of twenty amino acids, tryptophan is an essential amino acid meaning it is only taken in from the diet and not made by the body. L-tryptophan, the variation of the amino acid which is ingested, is used by the human body to produce the B-vitamin niacin. Niacin, in turn, is used to produce serotonin, a brain chemical that calms a person into sleep.
The myth about tryptophan
It is a common misconception that the tryptophan in turkey makes everyone sleepy after the Thanksgiving meal. Although tryptophan may play a chemical role in helping one nod off, it has this effect more prominently on an empty stomach when there are no other amino acids with which to compete. In truth, only a portion of the tryptophan from the turkey makes it to the brain to produce serotonin. Also, it takes larger quantities of tryptophan than what is present in the average serving of turkey to induce serotonin production to an extent as to cause sleep.
Tryptophan is also found in dairy products, fish, tofu, eggs, some seeds, nuts, and peanut butter. It would be reasonable to assume that eating a meal with any of these would make one sleepy just as turkey supposedly does, but they don't. Often dairy products and eggs are eaten for breakfast, a time when a person does not want to sleep. One more example disproving that turkey is what causes relatives to neglect the dishes in the sink on Thanksgiving.
The truth about the post-meal nap
Large quantities of food, particularly foods high in simple sugars and starches such as those found in a typical Thanksgiving meal, cause the drowsiness associated with holiday napping. The increase in blood sugar causes the body to release insulin. As the body quickly removes the sugar and the level in the blood drops, the body exhibits hypoglycemic symptoms such as drowsiness. This peak and fall is common with simple sugars and they are therefore avoided by runners or athletes the morning of a race or match. Pulling blood away from the brain to aid in digestion induces drowsiness also.
Alcohol consumption has its own sedative effect. This in combination with the bread, stuffing, turkey, potatoes, whipped cream, pie, carrots, or cranberries can make a nap seem like a good idea. It has been estimated that the typical Thanksgiving meal has 3000 calories.
Alternatives to avoid drowsiness
The best advice for avoiding an after meal doze on Thursday is to not pig out. Eat a little bit of everything, but not a lot of it all. To stop your blood sugar from plummeting, eat incrementally, a couple of little snacking meals rather than one large one. Another thing you can do is to have a cup of coffee or tea, caffeine helps offset the sedative affect. Also, limit alcohol and dessert consumption. Most importantly, a person could eat a balanced meal with steamed or fresh vegetables and lean protein; or just schedule in a nap.