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Why Do People Fall Asleep After Dinner?
It's time to talk about our good friend tryptophan. You know the stuff or at least you have heard about it.
Tryptophan is one of the 20 standard amino acids. It is also one of the essential amino acids for humans and many other organisms. Essential, meaning that it cannot be created by the organism and must be part of their diet.
All of these different amino acids, are the building blocks that make proteins which are absolutely vital for our survival. Proteins are involved in pretty much every process in the human body; from the structure of cells, to signaling between cells, to the catalyzation of processes and chemical reactions.
Proteins (which comes from the greek proteios, meaning primary) were originally named and reported by Jons Jakob Berzelius, a Swedish chemist in 1838. However, it was not until 1926 until they were really appreciated. This is because that is the year that James B. Sumner showed that urease, a known enzyme, was a protein.
Tryptophan was originally reported by Sir Frederick Hopkins in 1901. He noticed it when working with casein which is the predominant protein in dairy products (and a big reason why milk is white). He found that with 600 grams of casein, one could obtain 4-8 grams of tryptophan. In 1929, Sir Frederick Hopkins was awarded the Nobel Prize for his discovery of vitamins and how they are essential for our maintenance of good health.
So by now you are probably wondering what any of this has to do with why tryptophan is notorious for making people sleepy. Well to really understand these legos that connect together to build proteins, it's pretty important to understand their history. They have consistently been studied throughout time and have been found to be more and more essential to how we live.
In 1958 the worlds understanding of these complex structures (proteins) made leaps and bounds. In that one year 2 very large discoveries helped our understanding of proteins. Frederick Sanger mapped the entire amino acid sequence in insulin while Max Perutz and John Kendrew were mapping the sequences for hemoglobin and myogobin respectively.
Interestingly, all of these breakthroughs occurred in Cambridge, UK. Although Max Perutz and John Kendrew shared a lab, they had no real association with Sanger but Max Perutz was also known for overseeing the work done by James Watson and Francis Crick as they discovered the structure of DNA.
Tryptophan has been found to be the biological precursor to Serotonin and Niacin (vitamin B3). Serotonin, which is a neurotransmitter (chemicals that enable neurons like your brain to message to other cells) can be turned into melatonin (a sleep inducing hormone). It is this sedative hormone that supposedly causes your post turkey sleepiness.
Now, tryptophan can be found in a lot of different foods. One of the foods with the highest amount of tryptophan is actually egg whites. Cheese has a lot of tryptophan and pork has even more present than turkey or chicken (which are found to have the same amount of tryptophan).
So why the sleepiness after Thanksgiving and not a breakfast of scrambled eggs with pork sausage? Mostly because the really sedative effect of Thanksgiving dinner is more because of the over eating, excessive carbohydrate consumption (like break and sweet potatoes) and for adults, alcohol consumption.
So it's not really the tryptophan that makes us so tired after our big turkey meal. But hey, it's fun to blame our good friend tryptophan!
About the Author Sara Jones was a fine student but science was a source of frustration she didn't want her kids to suffer. She met Rick and Amanda Birmingham and realized their grasp of everyday science was the secret to making science fun. To learn more about the solution to science stress visit www.SuperFunScience.com
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