You may feel sleepy on Thanksgiving... but it's not the turkey.

Since Turkey-day is around the corner, I thought I would bring up the very popular myth that tryptophan in turkey is what makes us all feel groggy on Thanksgiving.  In an earlier post, I talked about how the amino acid tryptophan gets converted into serotonin, and then melatonin.  Melatonin, as you may or may not know is the "sleep hormone". It is secreted by the pineal gland to help regulate our sleep/wake cycles which follow a circadian rhythm of about 24-25 hours.  During the day, when it is bright and sunny we feel awake, then, as the day turns into night, we start producing more melatonin, and we get sleepy.  Considering this, it's not too hard to see why tryptophan became the scapegoat for our Thanksgiving day sleepiness, but the truth is tryptophan, or really turkey in general has gotten a bad rap.  First, tryptophan is a fairly prevalent amino acid, and there is actually plenty of it in most of the protein containing foods that we eat.  Furthermore, turkey does NOT contain a higher level of tryptophan than most other common meats, fish, and poultry.  For example, per 200 calorie serving, duck, pork, chicken, soy, sunflower seeds, several types of fish, and turkey all have about 440 - 450 mg of tryptophan, with turkey being the lowest in the group.  Of course, that being said, even if turkey did have significantly more tryptophan than other meats, it is still questionable as to whether normally consumed levels of tryptophan can make you sleepy.  While at first glance, the research seems to back the idea that tryptophan has sedative effects, these studies have used very large quantities to test for effects. For example, one study from 1975 suggested that consuming 5 grams of tryptophan (so, about 11 servings of turkey) did increase self-reported drowsiness, and a study conducted in 1989 found that a dose of 1.2 grams of tryptophan did not increase measures for drowsiness, but a dose of 2.4 grams did.  These studies suggest that you would have to eat a lot of turkey (like, over a pound and a half) to get an effective dose.  So, while it is possible that you may eat that much turkey on our most hallowed of gluttonous holidays, it is more likely that thanksgiving day drowsiness is the result of a coming together of many factors, a perfect storm if you will, of:
1. lots of food (which diverts bloodflow to the digestive tract),
2. much of the food is carbohydrate heavy stuffing and sweet foods like cranberry sauce, sweet potatoes, and desserts (which can cause an overproduction of insulin resulting in low blood sugar, and thus sleepiness, later on),
3. and then of course there are usually a couple of alcoholic beverages involved (with obvious sleep inducing effects). 
Add all of that up with being  in a nice, warm home, on a comfy couch, with football or parades or a fire flickering in the background, and what you have is a recipe for a nap.  I'm kinda sleepy just thinking about it.
Have a Happy Thanksgiving!