The human body normally destroys two million red blood cells every second in a process known as hemolysis. These cells are replaced by new red blood cells. But the process is accelerated in space, a phenomenon called "space anemia." In a microgravity environment, such as the International Space Station, the body's fluids shift and the blood loses about 10% of its water volume. To compensate, the astronaut's body will destroy 10% of its red blood cells to balance out cells and plasma. This has been known for decades, but it was assumed that with time, the rate of hemolysis would stabilize, and the blood would return to normal when the astronaut returned to earth.
However, an experiment involving 14 astronauts who lived on the ISS for six months found that three million red blood cells were destroyed every second, 54% more than normal, for the entire time they were in orbit. Thirteen of the astronauts had blood drawn soon after landing, and five were diagnosed as clinically anemic. But the big news was that a year later, the astronauts rate of hemolysis was still 30% higher than normal! This finding could have huge implications for long stints in space, as in the months of travel necessary to reach Mars. Read about space anemia at Ars Technica.
(Image credit: NASA)
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