Everyone “knows” that eating turkey on Thanksgiving makes you sleepy on account of its high content of tryptophan. But this isn’t true. Tryptophan gets a bad rap!
What is Tryptophan?
Tryptophan is an essential amino acid, a building block of proteins. It, however, is not manufactured in our bodies, so it must be obtained from protein in our diet.
Tryptophan is involved in the production of serotonin, the neurotransmitter associated with sleep. It is also a precursor of melatonin, the hormone involved in helping you fall asleep. Given these facts, the assumption that high levels of tryptophan in the blood (as in following a turkey feast) cause drowsiness is understandable.
It’s also incorrect.
Tryptophan is not the most abundant amino acid in turkey. Other amino acids are found in higher amounts, five of which compete for the same carrier protein used by tryptophan to cross the blood-brain barrier.
For tryptophan to be able to reach the brain and exert a sedative effect, it would have to be taken on an empty stomach. But that doesn’t happen on Thanksgiving, does it?
The Real Culprit? Carbohydrates!
What is far more likely to be responsible for that postprandial drowsiness is the high amount of carbohydrates consumed with the turkey: mashed potatoes, cranberries, breads, etc. There are two reasons for this.
First, a large, high-carbohydrate, high-fat meal will cause your stomach to distend. This in turn signals your brain to slow down the engine, so to speak, so that proper digestion can occur. (Fat and protein have a similar effects in the small intestine.)
Secondly, the high levels of carbohydrates trigger the release of insulin, which helps cells take up sugars and amino acids. This removes a lot of the competition for specialized transport proteins that tryptophan normally encounters. Increased uptake of the latter in the brain may lead to increased serotonin levels, inducing sleep.
Can Thanksgiving Sleepiness Be Avoided?
Eating slowly and pacing yourself will help. So will consuming more vegetables and plenty of water, and limiting or avoiding alcohol. Remember, though, it’s a holiday. It’s ok to indulge a little after appreciating how fortunate you are to enjoy such a feast. You can always take a short nap.
Happy Thanksgiving!
