However, the body has an antioxidant system made up of enzymes and molecules that protects against the damage caused by prooxidants by converting them into safe compounds. Examples of antioxidants are vitamins E, A, C and beta-carotene. These are available through diet or in nutritional supplements. Oxidative stress, a pronounced prooxidant state, is caused by the excessive production of free radicals or from the weakening of the antioxidant defense system, and is the cause of many pathologies, aging processes and is believed to be a possible cause of cancer. The space environment is obviously very different to that of Earth. The body has to adapt to weightlessness and the effect of background radiation. Nowadays, around six months is considered a safe amount of time to spend in space, allowing astronauts to carry out their functions as normal and allowing their bodies to readapt on return to Earth. Loss of red blood cell mass, volume of blood plasma, and hemoglobin has been continuously observed in astronauts during space missions. This phenomenon has been termed "spatial anemia" and the underlying mechanisms causing this are still not clear. This could be due to suppressed production of red blood cells or increased destruction of red blood cells. Many studies have demonstrated that red blood cells exposed to weightlessness have a modified flow and undergo damage to the cell membrane causing the release of hemoglobin to a greater degree. This experiment aims to determine the degree of "stress" that the red blood cells have undergone to bring about cell damage, the quantity of substances in blood serum that would prevent this damage (antioxidants), the damage that the red blood cell membranes have undergone, and the time it takes to recover. This will be done by measuring the antioxidant status of astronauts prior to and after space flight, and the time it takes to recover from oxidative stress occurring during space radiation exposure. Moreover red blood cells will be analyzed to evaluate their membrane composition and the activities of the enzymes involved in antioxidant defenses. This experiment will provide results that will help in finding methods to reduce the current effects of oxidative space anemia by, for example integrating appropriate dietary elements and natural compounds that act as antioxidants. These results will also impact on future longer-term space missions to, for example, Mars.
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