Space tourism sounds exciting, but anyone with existing anemia or heart conditions might want to rethink their dreams of chilling in outer space. In a study conducted by the Canadian Space Agency (CSA), a group of researchers found that a human body in space destroyed up to 54 percent more red blood cells than a body on Earth. This destruction led to astronauts experiencing anemia for at least a year after returning home. These findings were published in January in the journal Nature Medicine.
Humans have trillions of red blood cells carrying oxygen throughout our bodies. These cells don’t live forever; they can grow old and die. Red blood cells have a lifespan of approximately 120 days. Once their time’s up, the body will naturally destroy them using a type of white blood cell called a macrophage. Then, the body creates and releases new red blood cells to replace the ones that aged out. This whole process happens rapidly — our bodies typically create and destroy two million red blood cells per second.
But it only works this way if you never leave Earth.
Researchers noticed something different happened as astronauts came and went from space. The astronauts reported symptoms of anemia: a condition where your body isn’t producing the right number of red blood cells to send enough oxygen around. Anemia can cause fatigue, weakness, irregular heartbeats, and lightheadedness.
“Space anemia has consistently been reported when astronauts returned to Earth since the first space missions, but we didn’t know why,” said lead author Dr. Guy Trudel in a press release. Early researchers thought space anemia was the result of the body adjusting to a shift in bodily fluids. Astronauts tend to lose ten percent of the liquid in their blood vessels as their fluids move towards their upper body. Scientists at the time assumed that the astronauts’ bodies destroyed more red blood cells to make up for the loss, which accounted for the symptoms of anemia.
Dr. Trudel and his research team found that this wasn’t the case. “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.”
The team evaluated 14 astronauts (11 men and 3 women) for their research. Each astronaut went to the International Space Station (ISS) for six months, where they regularly measured the rate of red blood cell destruction through breath samples. Using these measurements, the researchers estimated that a human body in space destroyed 54 percent more red blood cells than usual — a total of three million cells per second.
Researchers also assumed the astronauts’ bodies continued to create just enough red blood cells to prevent them from experiencing severe anemia during their mission. But problems persisted even after returning to Earth. Although their red blood cell levels returned to normal within three to four months, their bodies still destroyed cells at a rate 30 percent higher than normal for at least a year.
“Thankfully, having fewer red blood cells in space isn’t a problem when your body is weightless,” Dr. Trudel noted. “But when landing on Earth and potentially on other planets or moons, anemia affecting your energy, endurance, and strength can threaten mission objectives. The effects of anemia are only felt once you land, and must deal with gravity again.”
This is a concern for future space travelers, especially those interested in heading to Mars someday. Anyone with existing anemia and health conditions that could be affected by it will likely have to be screened out of space travel. Astronaut diets and nutrition studies might have to account for red blood cell loss. Further studies are necessary to figure out how much worse the anemia can get during longer space missions. As well as to learn how long a human body can sustain such a high rate of red blood cell destruction.
As overwhelming as all that sounds, the findings from additional studies could benefit everyone — including Earthlings.
“If we can find out exactly what’s causing this anemia, then there is a potential to treat it or prevent it, both for astronauts and for patients here on Earth,” said Dr. Trudel.
Space anemia is but one of many things that can happen to astronauts conducting long-term missions in space. The low levels of gravity can shift the protective fluid surrounding their brains, reduce their bone density, and cause a rapid loss of muscle mass. High levels of radiation in space can also increase a person’s risk of developing cancer and other degenerative diseases.
