Is this true about space travel?

I was told that one of the little-known dangers for astronauts is that they cant stay too long in a zero- gravity environment;if you do so,your body will become permanently adapted to it and you will no longer be able to survive in normal gravity.Is this true?

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MougyWolf · 36-40, M

Yes, this is true. Astronauts who spend any more than a few years or so at a time can experience this. That's why it is important for them to stay as fit as they can up there, because the muscles atrophy unless we use them.

Mind you, I don't think it's like they would instantly die upon returning to Earth, but the longer you are in zero G, the harder it will be for your body to re-adjust.