During a six-month space mission, researchers found that the human body destroys about 54 percent more red blood cells than it normally would.

On Earth, our bodies destroy and produce two million red blood cells every second. But when you find yourself in the weightlessness of space, suddenly something curious happens. Researchers have discovered that your body in the universe suddenly makes short work of many more red blood cells. And that could have far-reaching consequences for future manned missions to the Moon and Mars.

Anemia in space

It has been known for some time that astronauts often suffer from anemia. Before the present study, however, this was thought to be a fairly short-lived condition; a rapid adaptation of the body to the fact that fluids move through weightlessness to the upper body of astronauts when they first arrive in space. “Studies from the 1990s already suggested that hemolysis (the phenomenon that red blood cells in the body break down, ed.) takes place in the very first days in space,” said researcher Guy Trudel in conversation with Scientias.nl. Why? Astronauts lose 10 percent of the fluids flowing through their blood vessels under microgravity. And to compensate, scientists suspected that 10 percent of red blood cells are also destroyed. After ten days in space, everything should be back to normal.

Study

But a new study now changes everything we thought we knew about this. In the study, scientists studied 14 astronauts during their six-month space missions. The researchers were able to measure small amounts of carbon monoxide in the astronauts’ breath. Each time a so-called ‘heme molecule’ – the deep red pigment in red blood cells – is destroyed, one carbon monoxide molecule is produced.

Astronaut Jeff Williams collects a breath sample aboard the International Space Station. Image: NASA

It leads to a surprising discovery. Because the researchers conclude that space anemia is not a short-lived condition, caused by the shifting of fluids. On the contrary. “It turns out to be a primary effect of staying in space,” Trudel says.

Red blood cells

As mentioned, our bodies destroy and produce two million red blood cells every second. The researchers found that the astronauts studied destroyed 54 percent more red blood cells during the six months they were in space. That’s 3 million disappearing red blood cells per second. These results were the same for both female and male astronauts.

Cause

According to Trudel, the findings are surprising. “Certainly the magnitude of the number of red blood cells being destroyed and their persistence,” he says. Why so many more red blood cells are destroyed in space than on Earth, Trudel does not yet know. “The difference is large, but the explanation for this is still largely unclear. There are some hypotheses, but they will need to be further explored.”

No problem

Although the team didn’t measure red blood cell production directly, they do believe that the astronauts studied made extra red blood cells to make up for the cells they destroyed. Otherwise, the astronauts would have developed severe anemia and experienced major health problems. “It turns out that astronauts function well in space with fewer red blood cells; they also have a smaller blood volume,” explains Trudel. “It is therefore not a problem to have fewer red blood cells when your body is weightless. But when you land on Earth and possibly other planets or moons, anemia can affect your energy, stamina and strength. The effects of anemia are only felt when you land, and you have to deal with gravity again.”

A year later

The effects of a space mission on your body also reverberate for a long time. Although red blood cell levels gradually returned to normal three to four months after returning to Earth, the researchers found that a year later, the astronauts were still destroying 30 percent more red blood cells than before their mission. These results suggest that the astronauts have undergone physical, structural changes during their time in space, which means that even a year after the mission, the red blood cells still have a different rhythm.

Missions to the Moon and Mars

According to Trudel, the findings have implications for future astronauts. “The longer the space mission, the worse the anemia,” he says. “This could have implications for long missions to the Moon and Mars.” According to the researcher, it is therefore important that we look for a conclusive explanation for the precise mechanism behind space hemolysis. “If we can figure out exactly what causes this anemia, it’s possible to treat or prevent it,” Trudel said. To increase the production of red blood cells, astronauts will have to follow an adapted diet.

Ask

Research into the phenomenon continues. There is no doubt that there is still much to be solved. For example, it is still unclear how the body can sustain the higher rate of destruction and production of red cells. “Our study identified significant knowledge gaps,” Trudel says. “Will the increased destruction of red blood cells and their compensatory production also continue during missions longer than 6 months? What about 1-year missions, or missions to the moon or Mars? And what is a safe interval between missions for astronauts who are sent on multiple missions?”

These are all important questions that need to be answered. But time is running out. Especially now that the plans to return to the moon and visit our nearest neighbor Mars are becoming more concrete. The hope is that we will know more in a few years’ time.