https://techcrunch.com/2019/04/11/twin-astronaut-study-suggests-interplanetary-travel-may-not-be-a-health-risk/

The human body “remains robust and resilient” after almost a year in space, according to a long-term, multi-institutional study of twins, one of whom lived aboard the International Space Station for 340 days while the other remained on Earth. These heartening results remove a potential barrier to crewed interplanetary missions — and just in time for us to start planning them.

The study, conducted by NASA and its partners on the American astronauts Scott and Mark Kelly, minutely monitored the twins vitals to see what if any changes occurred to the twin in orbit (Scott) that didn’t to the twin below (Mark). And changes there were, but nothing worrying enough that souls brave enough to go to space will second-guess their profession.