Ionizing radiation represents one of the biggest biological limitations in human space missions. In our daily life, we are protected from most space radioactive sources thanks to the terrestrial atmosphere and geomagnetic field. The aim of our research was finding the most important clinical consequences of exposure to ionizing radiation on astronauts’ health during a typical Mars mission. These data mostly come from radiotherapy patients and survivors to nuclear accidents. In addition, we explored and analysed specific chemical compounds which might be implemented in astronauts’ diets to improve their radioprotection during space missions.