NASA's twin study has revealed that a year in space in the International Space Station has little effects on human health
Little health effects after a year in space - space short science news

In a twin study carried out by NASA, no or only minor, mostly reversable, effects have been observed on a whole battery of physiological parameters in an astronaut who spent one year in ISS, and his twin brother, also an astronaut but remaining on Earth.

For example, some minor changes were found in the gut microbiome, but these reversed to normal within a short period of time. Some effects could be attributed to the return to Earth, such as increased inflammation markers and cognitive performance. Some gene expression changes and DNA damage had not normalized until six months after return to Earth.

Thus, one year in space does not seem to harm astronaut’s health, but the persistent molecular changes should be subject of future studies, scientists say.

Read the full story: University of Illinois at Chicago
Scientific publication: Science