A landmark study of astronauts shows the human body destroys over 54% more red blood cells during extended space missions. While space-induced anemia remains under investigation, addressing it is critical for deep-space exploration.
Eons of Earth-bound evolution have shaped our physiology, making prolonged space exposure a profound challenge. Mastering these effects is key to sustainable human presence on the Moon or Mars.
Known issues include vestibular dysfunction, fluid shifts, cardiovascular changes, muscle wasting, and bone density loss. Emerging research now spotlights spaceflight-associated anemia as another major concern.
Previously, space anemia was viewed as a short-term response to fluid redistribution upon orbit entry, normalizing within days. New evidence paints a different picture.
Published in Nature Medicine, researchers from the University of Ottawa analyzed breath samples from 14 astronauts after six-month ISS stays, using high-resolution gas chromatography to measure carbon monoxide (CO) levels.
Each heme breakdown—the iron-rich pigment in red blood cells—produces one CO molecule. Though not exclusive to hemolysis, about 85% of human CO production stems from red blood cell destruction.
On Earth, we produce and destroy around two million red blood cells per second. In microgravity, this study found over 54% higher destruction rates, consistent across male and female astronauts.
“Space anemia has been observed since early missions upon Earth return, but the cause was unknown,” explains Guy Trudel, MD, rehabilitation specialist and researcher at The Ottawa Hospital. “Our findings reveal elevated red blood cell destruction begins upon arrival in space and persists throughout the mission.”
Fortunately, this anemia appears reversible. Three to four months post-return, destruction rates began normalizing; even a year later, they remained 30% elevated.
In weightlessness aboard the ISS, no performance impacts were noted. However, upon landing on the Moon or Mars, reduced oxygen-carrying capacity could impair energy, endurance, and strength, potentially jeopardizing mission goals.
The precise mechanisms driving accelerated hemolysis in space—possibly in bone marrow, blood vessels, liver, or spleen—require further study. Bone marrow and spleen are prime suspects. Ongoing research will clarify how long the body can maintain this imbalance.
