A common belief is that tryptophan found in turkey is the cause of lethargy after a Thanksgiving meal. Is this true or simply a holiday myth?
Why is Tryptophan Blamed For Sleepiness?
According to most experts, turkey is not the primary reason for lethargy after a Thanksgiving meal.
Turkey contains the amino acid tryptophan, which helps the body produce niacin. Niacin in turn helps the body produce serotonin, which plays an important role in sleep. The logic behind the belief holds that increased tryptophan should mean an increased desire to sleep. This was an accepted conclusion by many consumers for decades, and tryptophan supplements were even marketed as a cure for insomnia until the FDA banned the supplement in 1990.
Here are some opinions regarding turkey, tryptophan, and lethargy:
How Stuff Works – “…nutritionists and other experts say that the tryptophan in turkey probably won’t trigger the body to produce more serotonin because tryptophan works best on an empty stomach. The tryptophan in a Thanksgiving turkey has to vie with all the other amino acids that the body is trying to use. So only part of the tryptophan makes it to the brain to help produce serotonin.”
Chemistry.About.com – Dr. Anne Marie Helenstine tackled the subject of Thanksgiving lethargy, and made the following observation:
“…the truth is that you could omit the bird altogether and still feel the effects of the feast. Turkey does contain L-tryptophan, an essential amino acid with a documented sleep inducing effect…However, L-tryptophan needs to be taken on an empty stomach and without any other amino acids or protein in order to make you drowsy.”
Scientific American – “…eating turkey does not translate to amplified serotonin production in the brain.”
National Geographic – “Contrary to popular belief, turkey’s tryptophan dose doesn’t cause drowsiness.” It is also pointed out that beef and soybeans contain higher concentrations of tryptophan than turkey.
PBS – In an interview with Dr. Howard Markel of the University of Michigan, we read, “…in order for L-tryptophan to really make you sleepy, you need to take it on an empty stomach and without ingesting any other types of amino acids or protein.”
WebMD – Author Lisa Zamosky points out that turkey contains less tryptophan than other poultry, but those aren’t singled out for lethargy like turkey is. Jackson Blatner asks, “When is the last time someone ate a chicken breast at a summertime barbecue and thought they felt sluggish?” Elizabeth Somer, MA, RD, adds, “It’s a myth that eating foods high in tryptophan boosts brain levels of tryptophan and therefore brain levels of serotonin.”
Washington Post – “…Cheddar cheese actually has more tryptophan than turkey does, and you don’t conk out every time you eat grilled cheese…”
What Causes Sleepiness After a Thanksgiving Dinner?
If turkey isn’t the culprit, then why is lethargy such a part of the post-Thanksgiving tradition? The experts have weighed in on this subject as well:
- Dessert – Scientific American quotes MIT’s Richard Wurtman, who stated, “Paradoxically, what probably makes people sleepy after Thanksgiving dinner is dessert. Eating carbohydrates increases brain serotonin in spite of the fact that there is no tryptophan in carbohydrates.”
- Fats – Dr. Helmenstine points out, “Fats also take a lot of energy to digest, so the body will redirect blood to your digestive system to tackle the job. Since you have less bloodflow elsewhere, you will feel less energetic after eating a meal rich in fats.”
- Carbs – Dr. Markel states, “Laboratory studies in both animals and human beings have demonstrated that carbohydrate-rich meals triggers the pancreas to release of insulin, the hormone that helps us breakdown and utilize sugar. But insulin also stimulates the muscles to take in large neutral branched-chain amino acids but not tryptophan, which is an aromatic amino acid. This results in a far greater ratio of L-tryptophan to branch-chained amino acids in the blood, and eventually, in the cerebral spinal fluid, the body fluid that bathes and cushions the spinal cord and brain. And now here’s the climax of all this organic chemistry and human physiology: the brain converts the L-tryptophan into serotonin that is eventually metabolized by the pineal gland into melatonin, a substance many travelers know as nature’s sleeping pill.”
- A Large Meal – Stanford’s H. Craig Heller points out that a large meal can lead to sleepiness: “Studies have indicated that stretching of the small intestine induces sleepiness and a protein–fat loading of the stomach induces sleepiness and, more blood going to the gastrointestinal tract means less going elsewhere. Also, there is the general phenomenon of parasympathetic tone—rest and digest—that is conducive to sleep.” How Stuff Works adds, “Most likely, it’s the whole traditional Thanksgiving meal that can produce that after-dinner lethargy. The meal is quite often heavy and high in carbohydrates — from mashed potatoes, to bread, stuffing and pie — and your body is working hard to digest that food.”
- Alcohol – Washing down your Thanksgiving meal with a depressant such as wine, beer, or champagne can also lead to sleepiness.
Among all of the items on the dinner table at Thanksgiving, turkey appears to be one of the lesser culprits in inducing sleepiness. Overall volume of food, carbs, fats, and alcohol all appear to contribute to that post-Thanksgiving dinner nap.
Updated November 23, 2015
Originally published November 2013