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ClemClem510 t1_jdgzswh wrote

That's a great question - our gut is a super interesting system, and microgravity does affect it in some ways, though obviously it still works up there.

One thing that's important to note is that your intestines are long, and honestly kind of all over the place. We're talking around 7 meters (20+ ft), going down, sideways, and sometimes up. Between that and the fact that we digest laying down a lot of the time, one realises that gravity pushing that food down isn't really the main driving force. What does most of that job is layers of smooth muscle, that contracts and pushes things along without you even being conscious of it. So the fact that things float up there is not a huge deal.

But lack of gravity does tend to do things to fluids, however. With gravity, they typically settle pretty well, with gases coming back up and separating from the liquids pretty cleanly. Since liquids also become floaty blobs in space, that stops being the case. This means that our usual ways of expelling gases - burping and farting - may stop just expelling gases. Notably, burps often come up with what feel like acid reflux, and, well, one shouldn't trust a fart in space (Google Apollo 10 floating turd for an interesting tidbit).

Another thing of note is that for many astronauts, arrival in space can be accompanied by space sickness, usually nausea, vomiting and a generally upset tummy. This is a digestive issue too, but one mainly caused by the sensory adjustment to space.

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MrGronx t1_jdh4fqn wrote

The amount of nausea and accompanied actually being sick is is officially known as space adaptation syndrome , but is unofficially measured on a scale known as the Garn Scale. The units range from 0 to 1 "Garn", where 1 Garn is as sick as an astronaut could possibly get.

The name comes from Republican Senator Jake Garn, the first sitting member of congress to go to space. He flew on STS-51-D as a payload specialist and as a subject on an experiment regarding space adaptation syndrome, and he didn't disappoint: he was so ill throughout the 167 hours of his mission that, ever since, astronauts coined the Garn Scale after him!

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Tjeetje t1_jdi2c74 wrote

Not the digestive system, but I was pretty shocked when our Dutch astronaut Andre Kuipers told that because of the lack of gravity you have a permanent feeling of a heavy cold with mucus flying free in your cavities.

I thought do you even feel good up there?

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ERSTF t1_jdiacn6 wrote

On the bright side he says he would do it again because it was his dream to go to space

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Cow_Launcher t1_jdhcj35 wrote

> ...gravity pushing that food down isn't really the main driving force. What does most of that job is layers of smooth muscle, that contracts and pushes things along without you even being conscious of it.

For anyone who wants to know more, this process is known as peristalsis.

Certain neurological conditions (e.g. Paralytic Ileus) can impact it and the results of this certainly prove that gravity doesn't play much of a part in the movement of food through the gut.

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