It’s everyone’s favorite post-Thanksgiving dinner excuse. “Excuse me, I’m just so sleepy after all that turkey. Must be the tryptophan!” You get to take a break from your family and sound smart at the same time. But you’re going to have to find a new exit line. The bird isn’t what’s making you stumble towards the nearest recliner.
Even though we only talk about tryptophan over the holidays, the biochemical compound isn’t unique to turkey. It’s present in everything from bananas to cod. More than that, tryptophan is an essential amino acid, with the emphasis on essential. Your body needs tryptophan to function and stay healthy, yet it can’t make the amino acid itself, so you need to get it from other sources.
Turkey is one of those reservoirs, but it isn’t really exceptional. The amount of tryptophan in the traditional Thanksgiving bird is comparable to the levels in chicken, beef, and even oats. Cheddar cheese has a greater proportion of the stuff, and some of the highest levels – 0.4 grams per a 100 gram serving – can be found in Alaskan Stellar sea lion liver. Even if you were chowing down on a pinniped this Thanksgiving, that still wouldn’t be enough by itself to make you sleepy.
That’s because dosage matters. The scientific connection between tryptophan and sleep comes from the amino acid’s connection to other bodily chemicals important for sleep. Tryptophan is needed to make serotonin – important for sending signals in your brain – and can be converted into melatonin, which is a hormone that helps regulate sleep. But in order to get these effects you need a great deal of tryptophan, significantly more than is present in your turkey or even a sea lion liver. Tryptophan supplements supposed to work as sleep-aids – which are not regulated by the FDA, mind you – usually contain about 0.5 grams or more of the amino acid.
Not that many around the Thanksgiving table make this connection. They’re more likely to quote a sitcom. As Snopes.com points out, a classic Seinfeld in which George tries to put Jerry’s girlfriend Celia to sleep with wine, turkey, and boring home movies probably has more to do with why the connection seems fresh in our minds. We just forget about everything except the turkey in the sketch, but it’s all the other stuff that’s actually more important.
Aside from travel hassles, family stress, and, for some, alcohol imbibed to alleviate those issues, the real culprits behind your holiday food coma are all the potatoes, yams, stuffing, and pie. We might call Thanksgiving “Turkey Day” but, in actuality, it’s Carbohydratepalooza, and those sides are what open the door to let tryptophan have a disproportionate effect.
The massive carb dump boosts the body’s insulin, Tanya Lewis reported for LiveScience, which removes most of the smaller amino acids from the blood. But tryptophan stays behind, and, now lacking competition, can affect the brain. To put it another way, Loyola University dietitian Kim Sasso says, “Turkey doesn’t make you sleepy; eating very large quantities of turkey, stuffing, potatoes and pie makes you sleepy.” So, lest you really take pride in looking and feeling like Jabba the Hutt, take it easy on the side dishes this holiday.
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IMAGE: The Vault DFW on Flickr
