SPACE IS HARD: We Finally Know The Full Extent of Space Destroying Astronauts’ Red Blood Cells.

In microgravity, the human body loses about 10 percent of the liquid flowing through our blood vessels, as blood accumulates in our head and chest. That’s why astronauts sometimes look swollen in their videos from the ISS.

For years, this was the explanation for space anemia. Perhaps the loss of red blood cells was our body’s way of compensating for a loss in blood volume.

But that’s not what the recent study found. Instead of equalizing the makeup of our blood, the loss of red blood cells appears to continue unabated throughout space flight.

Even after 120 days, when all the red blood cells in an astronaut’s body had been created in space, the loss of red blood cells continued at a similar pace.

“Our study shows that upon arriving in space, more red blood cells are destroyed, and this continues for the entire duration of the astronaut’s mission,” said Trudel.

When the astronauts were in space, the loss of red blood cells appears to have led to a higher-than-normal circulation of iron serum in their blood. Without as many red blood cells to transport iron around the body, the astronauts gradually approached anemia, which can be classified into mild, moderate, and severe.

When they returned to Earth, five out of 13 astronauts (one didn’t get blood drawn on landing) had reached clinically diagnosable levels of anemia, defined as the condition where the body doesn’t have enough red blood cells for its physiological needs.

About three or four months after landing, their red blood cell levels returned to normal. But even a year after their space flight was done, the astronauts’ bodies were still destroying 30 percent more red blood cells than before their trip to space.

Think of the study as (another) excellent reason to build much larger ring space stations, spun up to 1G.