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Space Travel Depletes Red Blood Cells but the Body Can Replenish Them Back

an astronaut inserting blood samples for MARROW into the Minus Eighty-Degree Laboratory Freezer aboard the ISS.
Credit: NASA.
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A study of 14 astronauts demonstrates that space travel depletes red blood cells and bone mass, but the body restores them post-mission using bone marrow fat. This process has implications for both space health and conditions on Earth, such as anemia and osteoporosis.

Key takeaways

  • Space Travel Impact: Study of 14 astronauts reveals that space travel causes red blood cell and bone loss, which is restored through fat stored in bone marrow upon returning to Earth.
  • Potential Health Implications: Astronauts' bone marrow fat depletion aids in red blood cell production and bone restoration; findings inform space missions and health conditions like anemia and osteoporosis.
  • Fat-Mediated Recovery: Fat in bone marrow serves as an energy source for red blood cell and bone production; research offers insights into immobility-related conditions on Earth and space.

Space travel destroys red blood cells

A study of 14 astronauts suggests that even though space travel destroys red blood cells and bones, the body manages to restore them after returning to Earth thanks to the fat stored in the bone marrow.  Published in Nature Communications , the study presents important considerations for health in space and on Earth.

“We found that in astronauts, fat in the bone marrow decreased about a month after returning to Earth,” says Dr. Guy Trudel , study author, rehabilitation physician and researcher at L'Hôpital d Ottawa, as well as a professor at the University of Ottawa. “We believe the body uses this fat to restore red blood cells and bone mass lost during space travel.

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The study builds on a previous study by Dr. Trudel which showed that astronauts' bodies destroyed 54% more red blood cells in space than on Earth, a phenomenon called space anemia. The research is part of MARROW , an experiment designed in Ottawa to study bone marrow health and blood production in space and funded by the Canadian Space Agency.

“Fortunately, anemia is not a problem in space when the body is weightless. On the other hand, when landing on Earth and possibly on other planets or moons subject to gravity, anemia could alter energy, stamina and strength and compromise mission objectives,” says Dr. Trudel. “If we could pinpoint precisely what is controlling this anemia, we would be able to improve prevention and treatment.

The new study included MRI scans of astronauts' bone marrow at different times before and after a 6-month mission aboard the International Space Station. The researchers found a 4.2% drop in fat in the bone marrow about 1 month after returning to Earth. This loss gradually reversed thereafter and was closely associated with increased red blood cell production and bone restoration.

"Because red blood cells are produced from the bone marrow and bone cells line the bone marrow, it is normal for the body to use the fat in the bone marrow as an energy source for the production of red blood cells and of bone," says Dr. Trudel . “We are eager to expand our research to other medical conditions on Earth.

Research also shows that young astronauts may have an increased ability to harness energy from spinal cord fat, and that in female astronauts bone marrow fat increased more than expected after one year.

Many of Dr. Trudel 's rehabilitation patients are anemic after a long illness that has limited their movement, and the anemia undermines their ability to exercise and recover. Anemia inhibits their ability to exercise and regain muscle and bone mass. “I hope this study will help people recover from long immobility on Earth as well as in space,” says Dr. Trudel . “Our study could also shed light on diseases such as osteoporosis, metabolic syndrome, aging and cancer, which are associated with increases in fat in the bone marrow. 

Reference: Liu T, Melkus G, Ramsay T, Sheikh A, Laneuville O, Trudel G. Bone marrow adiposity modulation after long duration spaceflight in astronauts. Nat Commun. 2023;14(1):4799. doi: 10.1038/s41467-023-40572-8

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