'Tis the season for Thanksgiving-themed tryptophan myth-busting, because America's weird ass genocide holiday is too boring for holiday click-chasers to come up with anything new. Look, you should know the following already as an adult: Eating a huge amount of food with probably some wine makes you sleepy because eating a huge amount of food on any day makes you tired. Processing food via the activation of the digestive system’s various glands and organs shares one of your brain’s major operating systems with basically one other function: slowing your body down. Rest. This part of the brain is the parasympathetic nervous system, sometimes known as the “rest and digest” system. Pooping and snoozing.
That’s the thing that is everywhere on the internet right now. But, as someone who writes about health on a fairly regular basis, I see the word tryptophan fairly evenly distributed through the year, regardless of proximity to the harvest. That’s because this particular amino acid is fundamental to your normal functioning, a day-to-day thing your body needs to consume in order to work right. More specifically, tryptophan is one of nine different amino acids humans need that are considered essential amino acids. Essential amino acids are known as such because your body can’t produce them; they only come from stuff you eat. For reference, egg whites will net you about four times the tryptophan as turkey per 100/g of food. Other better sources of tryptophan than turkey: sunflower seeds, cheese, soy products, spirulina, pork chops, and dried cod.
The real reason tryptophan is interesting is in its connection to serotonin, a neurotransmitter that helps regulate mood, particularly your mood’s (mood in its most general meaning) relationship to food. While serotonin's largest function is in regulating digestion, in action it's intimately related to good feelings for the simple reason that food means, fundamentally, not dying: energy and nutrients.
Put very simply: you consume tryptophan from the environment (in food) and your body facilitates chemical reactions that result in serotonin. With more serotonin in your synapses, you feel better. Many classes of antidepressants are designed to block processes that remove serotonin from your brain’s synapses, e.g. SSRIs. It’s a bit more of a reasonable fix than flooding your system with bonus tryptophan to be metabolized into bonus serotonin, though tryptophan supplements exist with a very big “potentially unsafe” caveat. To date, it’s been linked to 1500 or so reports of eosinophilia-myalgia syndrome (EMS) and 37 deaths.
As the one and only human parent of serotonin, tryptophan’s big implication isn’t with turkeys. It’s with mental illness. Everyone’s favorite holiday novelty molecule is implicated via serotonin in a range of illnesses, including schizophrenia, depression, and panic disorder. Note that this doesn’t mean it’s possible to eat your way out of a debilitating illness, though if you’re not eating at all or eating some very specific and bizarre diet targeting low or no tryptophan-sporting foods, I guess it’s possible.
Chemically speaking, the body isn’t just a collection of reservoirs containing different amounts of compounds you need that are depleted and repleted as if they were gas or antifreeze in a car. It’s more of a labyrinth of feedback loops in which some compounds signal need for others, some metabolize from something else into the compounds your body uses, some are junk or get in the way of useful activity of the body, some provide the right conditions for some or another physiological process to happen that results in yet more chemicals. It’s a pretty amazing mess and, neurologically, tryptophan as the source for seratonin lies somewhere near the center.
Pretty much any time the alt-medicine world hears that so-and-so chemical is needed for something in the body, its response is to 1) start selling it regardless of potential dangers and, 2) do whatever it can to help spread the notion that the body is indeed a bunch of reservoirs of different stuff and you should be filling it up with as much of everything as possible such that those reservoirs stay full.
In reality, the human body is really good at acquiring what it needs from a huge range of food. You can't actually increase the levels of tryptophan in your system by going heavy on foods with a lot of tryptophan in them. Person to person, tryptophan need varies a lot, but you are most definitely getting more than enough just by eating: while there isn't a set requirement of what you need to consume per day, the average suggestion I found was around 220mg. Meanwhile, the average human is taking in a full gram (remember: 1,000mg in a gram).
So there you go. The first time someone at the table mentions tryptophan you can be the one to start the first fight of the holiday season. Take no prisoners.