Now that Thanksgiving break is over and we’ve all moved up a notch on our belts (rightly so), it’s back to the sleep deprived college lifestyle. Fortunately, many of us gained a few extra hours of sleep on Thursday during the post Thanksgiving dinner nap… or at least your dad passed out right after dinner like all dads do on Thanksgiving.
You’re also probably familiar with how those who nap after the meal blame it on something called tryptophan. Maybe you yourself took a little cat nap this year, I know I did. This time around, I was the one to bring up tryptophan and my girlfriend was quick to say that tryptophan is not actually the reason America naps after turkey dinner. As with many of my blog posts this semester, lets find out what is really going on with something else we put in our bodies, Turkey.
Tryptowhat?
Courtesy of the University of Illinois at Chicago
Tryptophan, an essential amino acid, is found in many foods including turkey, eggs, chicken, fish, peanut butter and cheese. It is crucial for healthy growth in infants and is important for maintaining appropriate nitrogen levels in adults. Additionally, your body converts tryptophan into niacin and serotonin; serotonin is an important neurotransmitter responsible for healthy sleep and promotes stable moods. However, being an essential amino acid, our bodies cannot produce tryptophan on its own. Most people do not have an issue getting enough tryptophan but it is clear that it is an important macronutrient… but is it the culprit for our “thanksgiving nap?”
All of the above information courtesy of the U.S. National Library of Medicine
So why am I so sleepy??
Many attribute the “turkey daze” we feel on thanksgiving to an increase in serotonin due to the tryptophan found in turkey. This hypothesis does pass the sniff test, because as we found earlier, serotonin has long been associated with sleep and tryptophan is the primary precursor to serotonin in our bodies. Serotonin is created through biosynthesis that occurs after tryptophan has crossed the blood-brain barrier and interacts with the enzyme tryptophan hydroxylase in our neurons creating serotonin (Macalester.edu). However, according to an article on Scientific American’s website, it turns out that turkey is not actually responsible for “turkey daze.” Like any protein rich food, there are many amino acids found in turkey and tryptophan is actually one of the scarcest of the bunch. In fact, cheddar cheese, gram for gram, actually contains more tryptophan than turkey does (LiveScience). After thanksgiving dinner there are many amino acids circulating your bloodstream and for them to enter your brain they must cross the blood-brain barrier via the same transport proteins. Due to the fact that tryptophan is scare relative to the five other amino acids found in turkey, it must compete for the same transport proteins and it more often than not gets left behind says David Wurtman, a former professor at MIT (ScientificAmerican). He also goes on in the article to say, “Paradoxically, what probably makes people sleepy after Thanksgiving dinner is…dessert, eating carbohydrates increases brain serotonin in spite of the fact that there is no tryptophan in carbohydrates.” Furthermore, it may just be the sheer amount of food that we consume on this holiday that makes us so sleepy. “Studies have indicated that stretching of the small intestine induces sleepiness and a protein–fat loading of the stomach induces sleepiness,” says biologist H. Craig Heller at Stanford University.
So… whats the deal?!
Based on my own research, which includes eating a ton of turkey and then napping a week ago and a little over an hour of online reading and searching, I have found mostly speculation as to what is causes the post thanksgiving meal drowsiness. There seems to be a dearth of studies looking into the matter, which is understandable because science likely has more important issues to look into. But like all things, I imagine that it is a combination of things that are taking place to cause the drowsiness. Although the tryptophan is relatively scarce in our bloodstreams after eating turkey, it is still in our bloodstream and some of it is sure to cross the blood brain barrier as the other amino acids in turkey find their way across and become less concentrated in our blood stream. So, eventually serotonin biosynthesis should take place and that combined with the carbo overload and stretching of the small intestine would surely cause some turkey daze. However, if we were to conduct a study, it would need a single-blind randomized control trial where we have people eat identical thanksgiving dinners and then measure serotonin levels in the hour or two following the meal. It should be single-blind so that that we, or the researchers, do not know who ate the turkey and who didn’t to eliminate bias. This way we could isolate the effect of turkey on serotonin levels in the experimental (turkey) group and use the control (no turkey) group as a benchmark. In a study such as this it would be important to only test one dependent variable to steer clear of the sharpshooter problem. Moreover, randomization of both groups would allow for an accurate representation of how turkey or no turkey affects the average person.
In the end, turkey daze really isn’t an issue but more of an interesting phenomenon that takes place after thanksgiving. I couldn’t help but think as I was sitting around Thursday evening when I saw 5-6 people in the same room as me all asleep watching football that the turkey daze would make for a thought provoking blog post. It always interesting to learn a little of the science taking place behind things like this. Gobble Gobble.
amp6199,
I disagree that a single-blind randomized control trial would suffer from the researchers not knowing who got the turkey or not. In the case of a university-run study, a group of research assistants could administer the turkey to the subjects. This would be possible because the researchers could analyze both groups prior to the start of the study and allocate appropriate amounts of turkey to each participant BEFORE the experimental and control groups are chosen. If the study is indeed rejects the null hypothesis (turkey has no effect on serotonin levels), than it could be revealed to the researchers after they make their conclusions that the group in which they observed the higher serotonin levels was indeed the experimental group…. or perhaps the control group.
Let me know what you think!
I thought your idea to do a single-blind control trial on this issue was actually a pretty good idea. However, I think it would be difficult and here is why:
If only half of the people are eating the turkey, they will still all have to eat the same amount (or at least the same amount in a body weight ratio) in order for the study to be done properly. This poses a problem because if the researchers do not know who is eating turkey and who is not, how will they know what the right amount of turkey is? They will not be able to confirm that everyone had the same amount of turkey because they will never know who had the turkey, and the study will fall flat.
On the flip side, if the experimental subjects didn’t know that they were the only ones eating turkey, it would be very hard to make them eat the right amount of turkey. This may be anecdotal, but for me, I usually do not finish my turkey because I don’t really like meat that much.
Either way, I feel like the other side would catch on and the experiment would fail.
Personally, I am a vegetarian, so there was no turkey for me on thanksgiving, but I still felt really tired after eating. I feel like eating large amounts of food in general is bound to make a person sleepy and ready for a nap. A few different studies on this would be interesting:
1.) A double-blind control trial where one group ate a normal serving of food and another person ate several servings and see if that has any effect on the level of sleepiness.
2.) Another double-blind control trial where both groups eat the same amount of food but one group does eat turkey and the other does not.
This is a really interesting post right after the holiday though!! Thanks!
Kendall, I decided it would be better to do a single-blind randomized control trial because I think it would be impossible to give one group turkey and not give it to another group and not have them know if they got the turkey or not… they could taste/see/smell it!! Do you think it would be considered “double-blind” if the experimental and control group both had no idea what the experiment was looking at?
Let me know if you have any more input!
Passing out after a big Thanksgiving dinner due to tryptophan is a very real thing. I know this first hand since after this Thanksgiving and last’s dinner I fell asleep watching football on the couch. Although it also seems that desert and all the carbohydrates also contribute to the sleepiness myself and others experience after Thanksgiving dinner. I find it very interesting and kinda funny that people noticed a lot of people falling asleep after Thanksgiving dinner so they looked into the phenomenon to see what was causing the tiredness.
So it’s not just my dad who passes out on the couch snoring after turkey dinner? That’s refreshing to hear! What I understand from your post is that it is not necessarily turkey that makes us fall asleep but rather the immense amount of food we consume. You quoted that “stretching the small intestine induces sleepiness” and that is exactly what we do while sitting at the dinner table on Thanksgiving. With regards to the experiment you propose, I think you have a good idea for a study. I think you may have meant to say it should be a double-blind study where neither the experimenter nor participant knows who is eating the turkey. You could have the control group and the experimental group consume the same amount/weight of food, but only allow one group to eat the turkey and see what happens. You mentioned the lack of studies done on this, and I think you’re right that science may have other issues to look into first….but hey great blog post!