Tryptophan and the REAL Reason Your Uncle Falls Asleep Every Thanksgiving

Happy Thanksgiving

Thanksgiving in the United States is 2 days away. On this day each year, we gather together with loved ones and other people we can’t stand to give thanks for the fact that the Pilgrims built the first casino on Plymouth Rock and gave it to the Indians.

That’s not it? Wow, is my history book messed up.


In all seriousness, families all over America will be giving thanks for all their blessings in the best way we Americans know how – overeating! For most of those families, a staple of this traditional meal is turkey. Along with all the trimmings – mashed potatoes, yams, stuffing, cranberry chutney/jam/sauce, a vegetable or two that will largely be ignored and fresh baked rolls – it makes for a scrumptious holiday feast!

Which shortly thereafter devolves into the holiday snorefest, as engorged relatives flop into chairs and almost immediately fall asleep. There’s always the one uncle who falls asleep with a death grip on the remote, right after changing the channel to some PBS news show. There’s football, basketball and Christmas specials on and he wants to watch some boring, pasty old goofball in a bad suit talk about the war in Umbrellastan.

But I digress…


So what is it, exactly, about Thanksgiving dinner that encourages mass napping shortly thereafter?

Most people blame a tryptophan rush. Turns out, that’s not really fair.

The real culprits are more likely to be the massive overeating and the cocktails involved in the celebration. But let’s look at tryptophan. We’ll get to the bottom of your post-meal sleepy time shortly.

Tryptophan is one of the nine essential amino acids. This means that it is not produced in the body and must be acquired in the food we eat.


Tryptophan is important because it plays a role in protein biosynthesis. Since proteins are the second largest component of muscle (water is the largest component,) getting enough protein is crucial, especially if you want dem gainz!

It is also the precursor to two very important substances in the body, serotonin and melatonin. You definitely want tryptophan working to produce these two hormones!

Serotonin is a critical neurotransmitter, produced in both the gut and brain from tryptophan hydroxylase. 90% of it exists in the enteric nervous system in the gastrointestinal system, in cells called enterochromaffin cells. Serotonin is known as a key to feelings of well-being and happiness, but it plays many other roles. It’s involved in digestion, cognition, sensorimotor functions, bone mass regulation, organ development and sleep.


Melatonin is the sleep hormone. It’s involved in circadian rhythms, or the sleep-wake cycle, blood pressure regulation, it boosts the immune system and is a powerful antioxidant. Melatonin can be found in foods, including some fruits, but most notably in olive oil, wine and beer. We’ll explore more about this in a moment.

Niacin, or Vitamin B-3, can also be synthesized from tryptophan.


So tryptophan is a useful compound, for sure. What it isn’t, however, is the whole reason your Thanksgiving feast leads to so much napping and snoring (and maybe even drooling.) It’s gotten a bad rap over the years.

Thanksgiving feasts tend to be heavy on the starch and sugar. Potatoes, stuffing, yams, cranberries, bread, pies, whipped cream and all the other yummy stuff that goes with the bird.

Eating carbohydrates, especially the starchy or sugary types, can cause a temporary spike, and then a drop in blood sugar. When that happens, you get sleepy.


Add to that the all-day snacking on foods like cheese and beverages like beer and wine and you’ve got a perfect storm for chair-bound, remote-gripping sleep.

Activity matters, too. While some families may make football, cornhole or some other sporty activity a tradition, many take their inactivity very seriously. This maximizes the potential for the post-meal slump or comfy chair crash.

So what about tryptophan, then? Is it off the hook? Not quite. Tryptophan is found in a number of Thanksgiving-ish foods. However, contrary to popular belief, turkey has no more tryptophan than chicken. I’ve never heard of anyone complaining about tryptophan-induced drowsiness after eating chicken breasts.


Here’s a list of some common foods that have tryptophan, with the grams of tryptophan per 100 grams of food listed beside them.

Atlantic Cod (.70)
Chocolate (.19 to .85, depending on type)
Parmesan Cheese (.56)
Cheddar Cheese (.32)
Pork Chop (.25)
Turkey (.24)
Chicken (.24)
Beef (.23)
Salmon (.22)
Egg (.17)
Milk (.08)
Russet Potatoes (.02)

Tryptophan is metabolized in the body with the help of gastrointestinal microbiota. The bacteria Clostridium Sporogenes metabolizes it to a compound called 3-indolepropionic acid, or IPA. IPA is a highly potent neuroprotective antioxidant.


IPA is excellent at scavenging hydroxyl radicals. These rascals are highly reactive and can do damage to all kinds of molecules. Hydroxyl radicals can cause mutations to nucleic acids and make a mess of fat cells – and not in a good way! By kicking some butt on this free radical, IPA helps prevent cerebral ischemia, Alzheimers and neurological autoimmune diseases. (1)

Serotonin, melatonin, Niacin and a killer antioxidant for the brain! Tryptophan has even been tested as an anti-depressant, sleep aid and anxiolytic, meaning a compound that reduces anxiety. Some European countries still market it as a treatment for major depression.

Would including more tryptophan-laden foods help you sleep better, be less anxious and avoid depression? Unlikely. Studies have shown that dietary changes don’t increase blood levels of tryptophan.


Why not? It seems the transport system that brings tryptophan into the brain is at fault. Since it also transports other amino acids contained in protein foods across the blood-brain barrier. Since these neutral amino acids are also large, they take up space during transport, preventing the plasma concentration of tryptophan from boosting levels in the brain.

There’s evidence that supplementation with purified tryptophan can increase blood levels, as well as levels in the brain. However, their effectiveness has been shown to be lower than that of commonly used anti-depressants.

In a 2001 review of tryptophan on depression, only 2 of 64 studies showed tryptophan as more effective than placebos. In these cases, the authors stated that “the evidence was of insufficient quality to be conclusive” and note that “because alternative antidepressants exist which have been proven to be effective and safe, the clinical usefulness of 5-HTP and tryptophan is limited at present” (2)


There is one way in which tryptophan may “cause” your post-Thanksgiving feast nap time. But it really has more to do with carbohydrates than turkey. Here’s how it works.

  1. You eat the big meal with all the trimmings. You know, all the carb-y goodness.
  2. Insulin is released to deal with the elevated blood sugar.
  3. Insulin stimulates branched-chain amino acids to be taken up into muscles. Tryptophan is not among them. So blood concentrations of tryptophan rise significantly.
  4. There’s less “competition” at the blood-brain barrier, resulting in higher uptake levels of tryptophan into the cerebrospinal fluid.
  5. Tryptophan is converted to serotonin, then on to melatonin.
  6. Melatonin makes you sleepy.

Postprandial somnolence, or your post-feast nappy time, is actually the result of your heavy meal with all the carbohydrates. Tryptophan is kind of a victim here, rather than the perpetrator.


So on Thanksgiving, when you’re nodding off in the chair in front of the TV, don’t blame it on the tryptophan. At least not directly. Blame it on the stuffing, the potatoes, the yams and all the other “carb-y” goodness you enjoyed.

And wake up your uncle, get the remote and put the football game on!

Keep the faith and keep after it!

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  1. Zhang LS, Davies SS (April 2016). “Microbial metabolism of dietary components to bioactive metabolites: opportunities for new therapeutic interventions”. Genome Med
  2. Shaw K, Turner J, Del Mar C (2002). Shaw KA, ed. “Tryptophan and 5-hydroxytryptophan for depression”. The Cochrane Database of Systematic Reviews

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