The next "giant leap" for humans may be a trip to Mars, but having enough oxygen-carrying red blood cells for the journey might present a challenge, new research suggests.
Astronauts are known to experience "space anemia" - a red blood cell deficiency - while on missions, but until now it was thought to be temporary, reports Reuters.
Doctors attributed it to destruction of red blood cells, or hemolysis, resulting from fluid shifts as astronauts' bodies accommodated to weightlessness and again as they re-accommodated to gravity.
But Dr. Guy Trudel of the University of Ottawa, who led a study of 14 astronauts funded by the Canadian Space Agency, says this anemia is much more impactful:
“...we thought we knew about space anemia, and we did not. We had assumed that this was a very quick phenomenon of adaptation and nothing was going on. And now we're discovering that's not the case. Space has a primary specific effect on red blood cell regulation."
Normally, the body destroys and replaces nearly 2 million red blood cells per second.
Trudel's team found astronauts' bodies destroyed 3 million red blood cells per second during their six-month missions.
"... So I think the message is there is a knowledge gap here that we need to fill in terms of the mechanism, in terms of the countermeasures, in terms also of the planning of the mission. So will we need some blood products or artificial blood products on board of the mission to Mars, given the fact that there is destruction ongoing? Would we need iron supplements at one point if we can't recycle all of the iron to make new red blood cells and so on?"
Having fewer red blood cells in space is not a problem when your body is weightless, he added. But after landing on Earth, and potentially on other planets, anemia could affect astronauts' energy, endurance and strength.
His team reported on Friday in Nature Medicine that a year after returning to Earth, the astronauts' red blood cells had not completely returned to pre-flight levels.
The finding poses a challenge for space flight, especially for longer missions.
Researchers said even space tourists lining up for short trips might have to stay home if they are at risk for anemia, or red blood cell deficiency.