When astronauts spend a  lot of time in outer space, all sorts of scary-sounding changes happen: their muscles waste away,  their vision gets blurry, and their cancer risk goes up just to name a few.

Space travel is infamously bad for you. But what if it isn’t?

At least not always. It turns out that in some very specific cases, space travel can have some health benefits. And today, we’re going to highlight five of them. [♪INTRO] These days, almost half of  Americans have high blood pressure, which can lead to a number  of dangerous conditions: heart attacks, strokes, kidney disease, and more.

But a microgravity environment,  like the one astronauts experience as their spacecraft  continually falls around the Earth, naturally lowers  heart rate and blood pressure. There’s still plenty of gravity in outer space. In fact, the Earth is pulling on  the International Space Station, and all of its inhabitants,  at like 90% of what it does to everything on the planet’s surface.

But the perpetual freefall that  comes from the ISS travelling sideways at 8 kilometers a second  makes everything feel weightless. And in that weightless  environment, the heart slows down because it isn’t working against  gravity to move all our blood around. Space travel makes the heart’s job a lot easier.

Blood gets distributed more  evenly around the body, and it isn’t the only fluid this happens to. It’s why you’ll often see astronauts develop a puffy face after getting up in orbit. Your typical human body is, roughly, anywhere from 50 to 60% water by mass.

That’s a lot of fluid for  outer space to redistribute. And some of that redistributed fluid can help reduce the volume of blood inside you. When blood volume drops, so too does the pressure exerted on the  walls of your blood vessels.

But before anyone thinks about billionaires treating their hypertension  by popping up to space, there are some major caveats to this side effect. Because the heart doesn’t have to  work as hard as it does on Earth, space travel usually leads to  atrophy of the heart muscle. Plus, the effects don’t last after you come back.

Your blood pressure bounces back to whatever your “normal” is pretty quickly. And finally, there’s a reason NASA  has requirements for what your blood pressure needs to be to  qualify for their astronaut program. Strapping yourself to a rocket and getting launched into space puts a  lot of stress on the body.

Which you probably shouldn’t do if  you’ve got high blood pressure, or any of the increased risks of stroke  and heart attack that come with it. One of the classic side effects of space travel is that microgravity makes your bones weaker. If you’re floating around all the time, your skeleton doesn’t have to  do its job of holding you up.

But in the right dose, space radiation could help make your bones stronger. Radiation usually gets a bad rap, because certain forms of it can cause things like cancer. Or in sufficient quantities, just plain ol’ death.

But some research has shown that low doses of a radiation you get exposed to in space, called ionizing radiation might  actually slow the breakdown of your bones and increase the  density of minerals inside them. And if the problem of “weak bones  with not enough minerals” sounds familiar, it might be because it  goes by another name here on

Earth: osteoporosis. Our bones are constantly  getting torn down and rebuilt, by cells known as osteoclasts  and osteoblasts, respectively. But those osteoblasts get  less effective as we age, making fragile bones more of  a problem in older adults. Ionizing radiation can give  our bones a little boost in two separate ways: it can promote  the production of osteoblasts, while reducing the number of osteoclasts.

It’s also been shown to reduce inflammation caused by the immune system that can be harmful to bones. In fact, we already use some low  dose radiation therapy here on Earth, because reducing inflammation  can also reduce pain, and osteoarthritis can definitely hurt. But this is very much a case  of “the dose makes the poison”.

Right now, astronauts get  way too much space radiation, and it’s not just bad for their bones. But at lower doses like, if we  could get the shielding just right on the spacecraft it might be  helpful for keeping bones healthy. And maybe, with further research, we could even unlock a new therapy for people with osteoporosis who are too old to join  NASA’s next astronaut class.

But wait, I’m not done with radiation. Because in the right dose, space radiation might help repair your DNA. When our writer brought this up, I thought, “How could ionizing radiation  possibly be good for DNA?

It is infamous for damaging DNA molecules, hence the increased risk of cancer!” Well it turns out that some scientists have proposed an idea called radiation hormesis. DNA is the code that makes our bodies, except it’s “written” as nucleotides  instead of zeros and ones. And over time, errors can  and do appear in that code.

Some of these errors are typos  introduced as the DNA gets replicated, and some are caused by an  outside factor like radiation. But thankfully, your body  has a lot of ways to repair these errors in your DNA,  such as removing any mutated nucleic acids and swapping in a replacement, or creating a chemical reaction  that just undoes the damage. Radiation hormesis proposes  that a little radiation could kick those error-correcting  processes into gear encouraging cells to repair  damage better or faster, or to kill off damaged cells and sweep them up with our immune system’s cleanup crew.

Just like with our bones, though,  the radiation dose makes the poison. Too much radiation won’t give  the cells a chance to use their DNA repair powers, or just  causes way too much damage, killing them before they can make a comeback. And if enough cells die, then the  whole human might be toast, too.

And honestly, scientists aren’t in agreement on this particular hypothesis. Part of that is because it’s pretty dicey to do experiments that have so much risk to people. And we know irradiating them to  find out how much is safe will definitely lead to some pretty bad outcomes, so that would be highly unethical.

Meanwhile, researchers have done  experiments with cells outside a living human, and while  there have been some successes, radiation hormesis still isn’t widely accepted in the scientific community, at least in the U. S. The common wisdom has been “All  Radiation Bad!” for so long.

And just like every medical intervention, there’s a lot of variation in how  things affect individual people. So, it’ll definitely take time and  more incredibly rigorous studies about safety to change how we  deal with radiation exposure. We’ll get to more benefits of  space, right after this ad.

This SciShow video is supported  by our Presidents of Science! Thank you to TJ Steyn, Charlie Stanley, and McLaren Stanley for your continued support of everything we’re making here at SciShow. That includes myth busting popular misconceptions, exploring the unexpected  reasons some people end up with certain diseases, putting  ourselves in history or space or other times and places we can’t travel to… the list of SciShow topics is endless  because discovery is infinite.

To join our presidents of science and keep those discoveries coming to your  YouTube subscriptions feed, you can go to patreon.com/SciShow. Thank you for your support! Before we get to our final benefit,  here’s a sort of honorable mention: space travel could maybe,  possibly relieve your back pain.

At least until it makes it worse. But it’s getting a shoutout  because the side effects have inspired some cool treatments here on Earth. Some of the worst back pain happens when a nerve gets compressed by the disks  between your vertebrae.

Our spines are a sort of layer  cake, but instead of frosting, we’re made of cushion-y spinal  discs sandwiched between our bones. Bones technically do have spongy tissue in them, which really brings the cake analogy together Since most of us spend our days  with our spines roughly vertical even if we’re rocking that  remote desk job from our bed Earth’s gravity compresses our spinal cake. But in space’s microgravity,  your spine stretches out.

Astronauts can grow a few inches  thanks to this decompression. Although as with the blood  pressure, it’s only temporary. Now, the process behind this stretching is a bit stranger than the vertebrae just floating apart.

On Earth, gravity squishes water out of the discs when we’re upright during the day. Then at night, laying down to  sleep allows them to rehydrate. Space throws off this balance,  and the water sticks around, puffing things up and spreading the vertebrae out.

And if someone has damaged vertebrae where they’re compressed together,  this spreading out could theoretically relieve some of  the pressure that causes pain. A bunch of chiropractors and physical therapists actually use a similar technique here on Earth, known as spinal decompression therapy, to gently help relieve  pressure on a pinched nerve. Unfortunately, spending time on the ISS can cause way more problems  for a typical astronaut’s back than this possible benefit is worth for them.

Full-on microgravity can also  stretch out the spine too much, leading to even more back pain  once you’ve been in space for a few days, and a higher risk of problems  like sciatica upon return to Earth. Just like going to space  to treat your hypertension, it’s probably better to stick with the treatments that are literally more down-to-Earth. So let’s end on a more positive note.

Last but not least: space travel  can be great for your mental health! Sure, there are a hefty number of  mental health challenges in space: being confined in a metal tube  with deadly conditions outside, getting along with other  people in such a small space, being away from your family and friends for an extended period of time, and  having a ton of pressure on you to do precise and challenging tasks to perfection. But long term, it’s pretty well  known that going to space gives you a new, and often more  positive, perspective on life.

This is known as the Overview  Effect, characterized in research by a sense of awe, wonder, and,  quote, “transcendent experience” of seeing all of humanity  on our unique little planet. Well, maybe not seeing actual humans. We’re a bit too small for that.

Psychology studies also show that space leaves a hugely positive impression on astronauts, with a particular emphasis on  appreciating the beauty of Earth. Some astronauts even become  artists after coming back, finding a way to share the awe they experienced. For example, Apollo 12’s  Alan Bean, the fourth person to step foot on the Moon, took  up painting.

He once wrote, “It is my dream that on the wings  of my paintbrush many people will see what I saw and feel what  I felt, walking on another world some 240,000 miles from my  studio here on planet earth.” Meanwhile, research has also shown  that, after seeing Earth from outer space, astronauts often end  up valuing the collective good more. I think we can all agree  it’d be great if people cared more about other people, and about our planet. So while I’m not telling NASA to  lure a bunch of rich and powerful Ebeneezer Scrooge types onto  a rocket in the hope that they’ll have a change of heart, I’m  not saying it’s a terrible idea.

I mean, they’re kind of doing  it themselves, aren’t they? I’d also tell them to maybe  start with the ones suffering from high blood pressure,  osteoporosis, and back pain. You know, convince them a trip  to space might help with that. [♪OUTRO]