1/
Does the tryptophan in turkey really cause a food coma?
I've heard this repeatedly, while also being told that it is a myth. Let's have a look at the physiology of a Thanksgiving meal...
Does the tryptophan in turkey really cause a food coma?
I've heard this repeatedly, while also being told that it is a myth. Let's have a look at the physiology of a Thanksgiving meal...
2/
Before moving on, a relevant question: does turkey even have tryptophan?
Before moving on, a relevant question: does turkey even have tryptophan?
3/
According to the USDA, while it ain't cheese, turkey is still pretty rich in tryptophan (Trp).
But, notice that turkey is nothing special among meats. Depending on the type and cook, pork, fish, and chicken all have more Trp per serving.
ndb.nal.usda.gov/ndb/nutrients/…
According to the USDA, while it ain't cheese, turkey is still pretty rich in tryptophan (Trp).
But, notice that turkey is nothing special among meats. Depending on the type and cook, pork, fish, and chicken all have more Trp per serving.
ndb.nal.usda.gov/ndb/nutrients/…
4/
In fact, based purely on tryptophan content, it looks like a pork burrito with cheese and beans should be the ultimate food coma meal.
(@BostonChiefs: Don't tell the patient safety resident!)
Mmmm, is there any correlation between tryptophan and sleepiness?
In fact, based purely on tryptophan content, it looks like a pork burrito with cheese and beans should be the ultimate food coma meal.
(@BostonChiefs: Don't tell the patient safety resident!)
Mmmm, is there any correlation between tryptophan and sleepiness?
5/
In one experiment, participants were given 4 grams of tryptophan, leucine, placebo.
Result: those receiving tryptophan were more sleepy than those receiving placebo. The difference was seen as early as 45 minutes after ingestion.
ncbi.nlm.nih.gov/pubmed/6764927
In one experiment, participants were given 4 grams of tryptophan, leucine, placebo.
Result: those receiving tryptophan were more sleepy than those receiving placebo. The difference was seen as early as 45 minutes after ingestion.
ncbi.nlm.nih.gov/pubmed/6764927
6/
Why might Trp ingestion lead to sleepiness? Recall that Trp is a precursor of both serotonin and melatonin. These molecules are associated with sleep and sleepiness.
ncbi.nlm.nih.gov/pubmed/15575797
Why might Trp ingestion lead to sleepiness? Recall that Trp is a precursor of both serotonin and melatonin. These molecules are associated with sleep and sleepiness.
ncbi.nlm.nih.gov/pubmed/15575797
7/
To lead to sleepiness, Trp must cross the blood-brain barrier and enter the brain (then undergo conversion to serotonin/melatonin).
But, as a large neural amino acid (LNAA), Trp competes with other LNAA (eg tyrosine) for the mechanism of entry.
ncbi.nlm.nih.gov/pubmed/6115400
To lead to sleepiness, Trp must cross the blood-brain barrier and enter the brain (then undergo conversion to serotonin/melatonin).
But, as a large neural amino acid (LNAA), Trp competes with other LNAA (eg tyrosine) for the mechanism of entry.
ncbi.nlm.nih.gov/pubmed/6115400
8/
A series of experiments from the 1970s demonstrated that it isn't the absolute plasma concentration of Trp that matters. Instead, the ratio of Trp to other LNAA is key.
The higher the ratio, the higher the Trp content in the brain.
ncbi.nlm.nih.gov/pubmed/5077329
A series of experiments from the 1970s demonstrated that it isn't the absolute plasma concentration of Trp that matters. Instead, the ratio of Trp to other LNAA is key.
The higher the ratio, the higher the Trp content in the brain.
ncbi.nlm.nih.gov/pubmed/5077329
9/
Which of the following components of a Thanksgiving meal will increase the Trp to large neural amino acid ratio?
Which of the following components of a Thanksgiving meal will increase the Trp to large neural amino acid ratio?
10/
Foods with a high glycemic index (eg mashed potatoes) lead to insulin secretion, which causes skeletal muscle uptake of amino acids.
Because Trp is albumin-bound, less is taken up, leading to an increase in the Trp/LNAA ratio.
How cools is that!
ncbi.nlm.nih.gov/pubmed/3279747
Foods with a high glycemic index (eg mashed potatoes) lead to insulin secretion, which causes skeletal muscle uptake of amino acids.
Because Trp is albumin-bound, less is taken up, leading to an increase in the Trp/LNAA ratio.
How cools is that!
ncbi.nlm.nih.gov/pubmed/3279747
11/
Here's what'll happen to me on Thursday: I'll eat turkey (Trp!) and mashed potatoes (high glycemic index). The latter will increase the Trp/LNAA ratio, promoting movement of turkey's Trp into the brain. Trp will be converted to serotonin and melatonin.
Result: food coma
Here's what'll happen to me on Thursday: I'll eat turkey (Trp!) and mashed potatoes (high glycemic index). The latter will increase the Trp/LNAA ratio, promoting movement of turkey's Trp into the brain. Trp will be converted to serotonin and melatonin.
Result: food coma
12/
Of course, there is nothing unique about turkey and the Thanksgiving meal.
But, when you add the quantity/type of food alongside alcohol and a long day, it should come as no surprise that you're ready for a nap once the apple pie is served.
Happy Thanksgiving!
Of course, there is nothing unique about turkey and the Thanksgiving meal.
But, when you add the quantity/type of food alongside alcohol and a long day, it should come as no surprise that you're ready for a nap once the apple pie is served.
Happy Thanksgiving!
7/UPDATED
Thank you to @swapan55 and @KirkMMaxey for pointing out that LNAA are large NEUTRAL amino acids (not neural, as originally stated).
Thank you to @swapan55 and @KirkMMaxey for pointing out that LNAA are large NEUTRAL amino acids (not neural, as originally stated).
13/POSTSCRIPT
As has been noted by many (including @aaronecarroll in many formats), the amount of Trp in turkey consumed today (0.4g/cup) pales in comparision to the 4g used in the study in tweet 5.
We're ingesting low-dose Trp today.
Unless you eat the whole bird.
As has been noted by many (including @aaronecarroll in many formats), the amount of Trp in turkey consumed today (0.4g/cup) pales in comparision to the 4g used in the study in tweet 5.
We're ingesting low-dose Trp today.
Unless you eat the whole bird.
