Astronauts face a large number of other health risks during their stay in space. In a weightless environment, muscles aren't used as much, which can lead to them weakening and atrophying. Additionally, the lack of gravity causes bones to lose minerals at a faster rate, leading to bone density loss.

Suni Williams and Butch Wilmore, the two NASA astronauts who have been stuck at the International Space Station for more than 150 days and counting, are speaking out amid health concerns, reassuring the public they are doing well and explaining how they keep themselves healthy.