Debunking the tryptophan tiredness myth

No, it’s not the turkey making you tired. Time to pardon the turkey from the “turkey makes you tired” myth. Tryptophan (Trp) is an amino acid (protein building block). In addition to its role as a protein letter, Trp is a precursor to the chemical signaling molecules serotonin & melatonin that help regulate mood and sleepiness and stuff. But it’s not that simple!  
  

  
Trp can be converted into serotonin (5-hytdroxytryptamine (5-HT) which can act as a neurotransmitter that lets brain talk to other cells to regulate things like mood, appetite, sleep regulation, bone metabolism, and GI motility. And, in the brain’s pineal glad, it can be further converted into melatonin (N-acetyl-5-methoxytryptamine). As the “gland” in pineal gland suggests, melatonin is a hormone. It helps regulates sleep & wakefulness  
  
It’s only made in the pineal gland and the retina, not other places in your body because the other places don’t make the needed enzyme (reaction mediator/speed-upper). The pineal gland is a tiny gland in the middle of your brain and it secretes melatonin into blood & cerebrospinal fluid (brain juice). This synthesis & secretion increases during the dark period of day, so you get sleepy at night.   
  
And you get the turkey makes you sleepy myth you probably heard around Thanksgiving. So let’s tackle it. 1st of all, turkey doesn’t have any more tryptophan than other meats (cheese actually has even more). 2nd of all, when you eat Turkey at Thanksgiving, you’re probably eating a lot more than just Turkey - likely you’re also eating a lot of carbs. And this leads to the release of a hormone called insulin. It’s mainly known for its role in telling cells to let in and use glucose (blood sugar) (it’s either not produced enough or not well-recognized in patients with diabetes). But it also has the role of telling cells to let in LNAAs (Large Neutral Amino Acids), a class which, in addition to Trp also includes Tyr, Phe, Ile, Leu, Val, and Met. note: some sources also include His in the list   
  
In your blood that Trp’s pretty tied up. Turns out that the indole ring is good at binding to serum albumin, an abundant protein in your blood. So Trp has a hard time getting in, but the others are free-er so they can get into your muscle cells, etc. This leaves Trp with less competition when it gets to the brain and has to cross the blood-brain barrier. It still has to compete with all those other guys here, but it’s starting with an advantage and it likes the transporter here better. So more Trp gets taken in and used. And, although this situation might lead to increased Trp crossing the blood-brain barrier into the parts of your brain where serotonin is made, those parts don’t make the enzymes you need to go all the way to melatonin.  
  
Further exonerating the turkey, the part that does have the needed enzymes, the pineal gland, is actually not protected by the blood-brain barrier. So it’s seeing the same “more competition to get in” blood as the rest of your body.   
  
Bottom line: The biggest part of the tiredness is probably just your metabolism working really hard to try to breakdown your big meal. And potentially some alcohol consumption… So it’s really unfair to blame the turkey, especially since you’re eating it…   

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If you’re celebrating Thanksgiving, please donate to SACNAS, the Society for the Advancement of Chicanos/Hispanics and Native Americans in Science. They do, great, important work, and they deserve our gratitude and support.   

[CELLPERSPECTIVE]

Great video!

And a special thank you to the decarboxylaze enzyme for converting 5-hydroxytryptophan to seratonin for the happiness as I shove mounds of turkey into my stomach.