Normally, people debate about the benefits of biomedical research in space from the knowledge gained and the skills developed. It is rare, however, to discuss negative effects a space flight has on an astronaut’s body.
On a space trip, with no gravity, fluids in legs and the lower part of the body will move upwards towards the head, resulting in a swollen face, an occasional headache and congestion. In the first few days of getting acquainted with zero gravity, feels of dizziness and having an upset stomach are fairly obvious tokens. Luckily, this feeling will disappear after three or four days. In space, an astronaut’s bones and muscles will get weak unless he or she has adopted a regular exercise schedule before taking a space flight. When returning to Earth, getting used to gravity again sometimes makes astronauts dizzy or queasy. Depending on the flight duration, it may take them from two days to several weeks to feel normal again.
After astronauts come back to Earth, unforeseen consequences are much more serious. With less gravity, the body doesn’t really need a strong skeleton, causing bones to weaken. Additionally, because of lack of use, astronauts’ muscles soon lose strength. Their heart has trouble pumping oxygenated blood to all parts of the body and breathing fully is difficult as well. Their digestive system is less efficient, affecting their appetite negatively. They may also suffer from a weakened immune system which limits their ability to prevent diseases. Additionally, various forms of cancer are a predictable result of high levels of solar radiation.