The Thanksgiving Sleep

One of the persistent questions that come up at Thanksgiving, by well-meaning distant relatives trying to fulfill their annual social obligations by making conversation with the doctor in the family, is why turkey makes people sleepy.  Is it, they wonder while showing evidence of scientific literacy, because of all the tryptophan? 

I typically answer that it's an interesting question.  As questions go, however, it's really not that interesting.  But I, too, have my annual social obligations.  So helping other people fulfill theirs helps me fulfill mine.

Even without the burden of family relationships, however, this question is a relevant one not just because of the recent holiday but also because of some research studies I've been reading that leave me both interested and disturbed.

No, it's not the turkey.  Turkey does have the amino acid tryptophan in it, but no more than many other foods.  It's the gigantic overeaten orgiastic tsunami of food that makes us sleepy.  The more stuff we have to digest, the more our bodies move blood flow to our intestines.  That leaves less blood for less essential organs such as, for example, the brain.  In order to metabolize just one slice of pie (though there were, to be fair, 3 different types of pie and a cake of some sort; so it was just one slice--of each), our body has to pump insulin into our bloodstream.  That can cause fluctuations in our blood sugar that leave us very sleepy, too.  So if you think that the vegan tofurkey is going to sharpen your wits, it won’t if you eat the same excessive amount of it and everything else as your mainstream relatives do.  Here in Berkeley, needless to say, one has the luxury of access to exotic and gourmet foods.  And to foods like tofurkey.  (For readers naïve to the special experience tofurkey provides, I would guess that fewer people choosing this product for thanksgiving end up as profoundly overindulgent at the thanksgiving feast.  Whether this is because of superior self-restraint or inferior sensory experience of the food itself would be a matter of speculation.)

Tryptophan is not manufactured in the body, so it's called an essential amino acid.  But it's in lots of common foods, so we usually get plenty of it.  In the body, it's used for many purposes, including the production of the neurotransmitter serotonin.  Serotonin also has many functions that we know of, and seems to be very important in the regulation of our mood.  Many antidepressant medications are designed to increase levels of serotonin.  There are several over-the-counter tryptophan products available at the drugstore.  But it's not a feel-good pill.  Too much serotonin can cause tremors, blood pressure problems, muscle damage, and worse.  This is called serotonin syndrome.  That's assuming that the tryptophan product isn't contaminated in some way.  Twenty years ago a new disease emerged called eosinophila-myalgia-syndrome.  Though symptoms varied, probably over 1000 people had painful symptoms and a couple of dozen died.  All had been taking tryptophan.  Tryptophan is sold in the United States as a supplement, unregulated.  It's sometimes sold as something to help you sleep, since so many people believe it's the component in turkey that causes sleepiness.  And some of the tryptophan is converted to serotonin which is then converted to melatonin which helps some people get to sleep.  How much tryptophan do you need to take to increase your melatonin levels enough to have an impact on your sleep?  Given that the tryptophan in your thanksgiving turkey isn't what's making you sleepy, it might be quite a bit.

None of this is the research I read.  What I found out about was the appealing idea of adding tryptophan to baby formula and baby cereal.  The idea is straightforward enough.  Feeding the baby the right product at bedtime could be helpful in keeping the baby asleep longer, and everybody is happier.

But I worry about a baby getting one of these nasty syndromes.  How much additional tryptophan is too much?  Both human milk and cow milk have about the same proportion of tryptophan, so either formula or nursing is likely safe in this regard.  But extra?  Of course there is a philosophical objection, even if it were completely safe.

Babies cry.  It's one of the main ways that they communicate.  They have other talents, to be sure, but they often cry when the need something from us.  Given that it may be inconvenient and frustrating to try and figure out what it is that they need, it has always been tempting to find a way to 'help' the baby stop crying.  There's a big difference between getting the baby to stop crying and meeting whatever its needs might be.  In the 19th century, there were several very effective nutritional supplements and tonics marketed for quieting babies.  The opium in them seemed to help right away.  It suppressed hunger, reduced pain, caused sleepiness.

I'm not claiming that tryptophan is equivalent to opium.  But I ask myself, 'who is this helping?  What patient am I treating?  Is the baby going to be better because of this?'  So, for now, I'm suggesting that parents resist the urge to give their babies extra tryptophan.  Wait until the kid can just eat turkey like the rest of us.