November 6, 2010

The Lies of Thanksgiving: Tryptophan

In a world, filled with corruption (and stuffing), one man looks to peel back the lies and deceit of this holiday season. In my quest for truth about this holiday season I have stumbled upon the BIGGEST CONSPIRACY since the invention of the aglet (for their purpose is sinister indeed). I stared at the radio, the television, the internet, all feeding me the same horrific lie:

Possibly the best picture I've ever found
Turkey makes you sleepy

I knew the truth, I had to tell it to the world. But I knew THEY would try to stop me. THEY, the old wives tales and embedded ideas of the past that led people astray. I needed to show the truth, to uncover....The Lies of Thanksgiving!

Cue title drop

Yeah, I'm getting weirder... Anyway.

So we hear the same thing every year: its Tryptophan in turkey that makes one sleepy during this gluttonous holiday.

This is, of course, Grade A bull. The truth isn't that simple, and doesn't fit into a single line like "Tryptophan in Turkey causes sleep". There is another reason for sleep, that is directly correlated to this holiday.

Before I get into the details of why, let's first talk about Tryptophan and what it is

What we're talking about: pretty isn't it?
Tryptophan is an amino acid, which, for those of you who don't know, are the building blocks of proteins and enzymes within the body. Tryptophan is one of several amino acids that is 'essential'. In other words we cannot produce these amino acids on our own, we have to take them in through protein (meat, beans, seeds etc...). This is also true of about half of all amino acids (the other half are either produced from amino acids, or are made via other mechanisms).

Firstly, tryptophan is not the most common amino acid within protein. There simply just isn't that much there. I've attached a brief graph below
And I made it myself too!

As you can see, while Tryptophan IS present in turkey, it is no more so than, say beef, chicken or pork, all of which are of comparable content. So then, why do we not associate eating meat (or eggs, or seeds) with being drowsy?

Serotonin and melatonin pathway from Tryptophan

There is some truth behind the myth, Tryptophan is used to produce serotonin. Serotonin is a well known contributor for 'well being' and being 'calm', and in fact an abundance of the stuff WILL make you fall asleep, so there is some credence to this myth. Eating turkey on turkey day WILL make you content and happier. Which is good because the opposing force of your family will try to bring you down.

In fact, serotonin is a very important little chemical, as its deficiency has been linked with sudden infant death syndrome, as well as depression. As a result, it is used as an anti-depressant and will make you fall asleep in high enough dosages... but not the dosage we're talking about when it comes to turkey.

Sleep itself is a complex mechanism, associated with many different chemical neurotransmitters. This includes Melatonin, which also is synthesized from Tryptophan. Melatonin itself does not actually 'cause' sleep. It has far too many other uses in the body as an antioxidant and for the immune system. Another of the key chemicals (and one many people know about) committed to sleep is dopamine, which isn't made from Tryptophan at all but instead from another amino acid called Tyrosine (which turkey, again, has about an average level of).

No, in fact the turkey itself has little to do with why we find ourselves in a veritable coma while watching football (bonus points for  Detroit Lions game "watchers"). The cause is actually the sheer amount of food that we eat. Thanksgiving is, after all, perhaps the most gluttonous holiday of the year

This occurrence is called Postprandial somnolence or, as it's more commonly called, a food coma. This is caused by two things: a lowered state of energy, and general sleepiness caused by neurochemical and hormonal changes in the body, related to the rate glucose (what we get energy from) enters the body.

So let's break this down.

When you eat a lot of food and it hits your stomach and small intestine, it causes a shift in your body's priorities. The activity in your sympathetic nervous system (which controls eyes, heart lungs etc) is down regulated while the activity in your parasympathetic nervous system (which controls the glands and organ for digestion) is up regulated. This shift results in the body being at lower energy and having a desire to rest. The bigger the meal, the more this affects the subject.

In addition, when eating foods with a high glycemic index (so something high in carbs), glucose is absorbed rapidly in the digestive tract and then sent into the blood stream. For people without diabetes, this then sends a massive burst of insulin out to try and keep the blood glucose levels maintained. The sudden burst of insulin induces many other non-charged amino acids to be taken into the muscles...except for tryptophan. This lowers the ratio of these other amino acids in the bloodstream to tryptophan, making tryptophan more preferable to cross the blood brain barrier. Once inside the brain, tryptophan indeed becomes serotonin and melatonin. The increase of both of these substances in the brain directly correlates with sleepiness and can be measured. But correlation does not equate to causation. The serotonin and melatonin levels result from overeating, not the the quantities of tryptophan in the turkey

So, there we have it. The Tryptophan in the turkey is not the trigger that makes people tired. It is the amount of carbohydrates and sheer amount of food consumed that does it.

Thanks for reading,


Have a good, restful, Turkey Day


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