Nausea

There’s a lot of traveling going on this time of a year via car, plane, train or boat, and somewhere this very second, a 10-year-old is looking up from the book she’s been reading in the back seat of her parents’ station wagon and speaking the words that, for many people, define the whole summer traveling experience:

“I think I’m going to be sick!”

Emesis (a very polite scientific word for throwing up) is a survival trait. It exists primarily to get poisonous substances out of our bodies before they can do any harm. Sometimes it is also called upon to lighten the load on an overtaxed digestive system.

Throwing up is triggered by “afferent” nerves in the digestive tract, which keep the brain apprised of the stomach’s condition: empty, full, or one-more-bite-of-pecan-pie-and-you’ll-be-sorry stuffed. These nerves can also detect chemicals that only show up when food is rancid or spoiled.

Fortunately for the state of carpets everywhere, we get advance warning of throwing up in the form of a tight throat, surging saliva, a cold sweat and other symptoms, collectively called nausea. Precisely why we get this advance warning isn’t clear, but one theory is that nausea is nature’s way of punishing us for doing whatever we’ve done to make us feel that way, so we’ll never do it again.

The vomit reflex itself, once it begins, is pretty well impossible to stop. First the stomach muscles relax, then the small intestine pushes its contents–an acidic mush–up into the stomach. The stomach muscles contract and squeeze the mush into the esophagus. The esophagus, which normally uses rhythmic muscle contractions to push food downward, now shifts into reverse and pushes food upwards to the mouth, and from thence–well, you know the rest.

It makes perfect sense for us to throw up spoiled or poisonous foods. But why do various forms of transportation, plus any number of rides at the midway, affect us the same way? What sort of survival trait is that?

It probably isn’t one. Motion sickness appears to be an unfortunate side effect of transportation technology. Motion sickness wasn’t a problem for our australopithocene ancestors: nobody ever got footsick. But then somebody had to go and invent boats and wagons, and eventually cars and planes and space shuttles and the Tilt-A-Whirl, and in the process, they invented motion sickness.

Scientists say that, on a bumpy airline ride or a cruise in rough water, as many as 80 percent of the passengers will be sick. The cause appears to be a disagreement among various parts of our body as to what kind of motion we’re being subjected to.

Our three main ways of monitoring the movement of our bodies are our eyes, our inner ears and our pressure-sensor system (which tells us, for example, when we’re firmly seated in a chair). In a vehicle, these systems send conflicting signals. Your pressure sensors tell you you’re just sitting there. Your eyes may tell you you’re not moving at all (if you’re, say, reading a book) or they may tell you you’re moving very fast (if you’re watching scenery flash past.) And your inner ear, which has three tubes, each oriented in a different way, through which liquid sloshes as your body changes orientation, is giving you very precise readings on all the swaying and bumping your other systems aren’t noticing. The conflicting information confuses your brain, which responds with dizziness, light-headedness and disorientation–the same symptoms brought on by many toxic substances. Figuring you may have been poisoned, the brain initiates nausea.

There are drugs that can help, but an even simpler remedy, which recent studies have shown to be just as effective as drugs for some people, is ginger: eat ginger candies, drink ginger tea or take it in tasteless pill form.

Eat light foods; the less overloaded your stomach is, the less likely it is to rebel. But do eat something; an empty stomach is an unhappy stomach (one of my basic philosophies). Alcohol won’t help and may make things worse. Sit in the front seat of the car, not the back, and don’t ride backwards in a train or bus. And don’t read!

Lord Nelson was seasick every time he went to sea, and Lawrence of Arabia got sick riding camels (having ridden one myself, I’m not surprised). Think about these famous sufferers the next time you’re bouncing over a Saskatchewan highway in the grip of carsickness, and maybe you’ll feel better.

But probably not.

Permanent link to this article: https://edwardwillett.com/1996/08/nausea/

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