A groundbreaking study has revealed how space travel can result in reduced red blood cell counts, also known as space anemia.

According to a study published in Nature Medicine, the bodies of 14 astronauts destroyed 54 percent more red blood cells in space than they would on Earth.

“Space anemia has consistently been reported when astronauts returned to Earth since the first space missions, but we didn’t know why,” says Dr. Guy Trudel, lead author. “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.”

Space anemia was previously assumed to be a speedy reaction to fluids migrating towards the astronaut’s upper body when they initially arrived in space. Astronauts lose 10% of the liquid in their blood vessels as a result of this process. It was believed that astronauts quickly destroyed 10 percent of their red blood cells to restore balance, and that red blood cell control returned to normal after 10 days in space.

This is not what Dr. Trudel’s team thought. They found that the red blood cell destruction was a direct result of being in space, not caused by fluid changes. They proved it by measuring the breakdown of red blood cells in 14 astronauts throughout their six-month space missions.

Every second on Earth, our bodies make and destroy 2 million red blood cells. During their six months in space, astronauts destroyed 54 percent more red blood cells, or 3 million every second, according to the study. Both male and female astronauts had the same outcomes.

In order to make this discovery, Dr. Trudel’s team came up with new techniques and methods to accurately measure the amount of red blood cells that were destroyed. These techniques were then used to collect samples on the International Space Station. They were able to precisely analyze the minuscule levels of carbon monoxide in astronaut breath samples at Dr. Trudel’s lab at the University of Ottawa.

One molecule of carbon monoxide is produced every time one molecule of heme, the deep-red pigment in red blood cells, is destroyed.

While the team did not directly quantify red blood cell creation, they believe the astronauts produced more to compensate for the cells they destroyed. Otherwise, the astronauts would have developed severe anemia and faced serious health issues in space.

“Thankfully, having fewer red blood cells in space isn’t a problem when your body is weightless,” adds Dr. Trudel. “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.”

Five of the thirteen astronauts in this study were clinically anemic when they landed, while one of the fourteen astronauts did not have blood drawn on landing. Researchers discovered that space-related anemia may be reversed, with red blood cell counts gradually returning to normal three to four months after returning to Earth.

Interestingly, one year after the astronauts returned to Earth, the scientists repeated the measurements and discovered that red blood cell breakdown was still 30 percent higher than before the journey. These findings show that structural changes in the astronaut’s body occurred during their time in space, which may have affected red blood cell regulation for up to a year after long-duration space missions.

The discovery that space travel increases red blood cell destruction has several implications. First, it supports screening astronauts or space tourists for existing blood or health conditions that are affected by anemia.

Second, a recent study by Dr. Trudel’s team found that the longer the space mission, the worse the anemia, which could impact long missions to the Moon and Mars. Third, increased red blood cell production will require an adapted diet for astronauts. And finally, it’s unclear how long the body can maintain this higher rate of destruction and production of red blood cells.

These results could be applied to life on Earth as well. Most of Dr. Trudel’s patients are anemic after being sick for a long time and having restricted mobility, and anemia makes it difficult for them to exercise and recover. Anemia has been linked to bedrest, however the exact mechanism is uncertain. Dr. Trudel believes the mechanism is similar to that of space anemia. During future bedrest experiments on Earth, his team will look at this theory.

“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,” adds Dr. Trudel.

Source: 10.1038/s41591-021-01637-7

Image Credit: NASA

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