Long Time In Space Can Cause Porous Bones, Weightlifting Is Necessary

Astronauts experience bone loss on long space flights. (photo: doc. unsplash)

JAKARTA- The experience of being in outer space, for a long period of time, has a negative impact on humans. A study of bone loss in 17 astronauts aboard the International Space Station provides a more complete understanding of the effects space travel has on the human body and the steps that can reduce it.

The results of the study are important insights ahead of possible future ambitious space missions.

This research collects new data on bone loss in astronauts caused by microgravity conditions in space and the extent to which bone mineral density can be recovered on Earth.

The study involved 14 male and three female astronauts, aged 47 on average, whose missions ranged from four to seven months in space, with an average of about 5 months and 15 days.

A year after returning to Earth, the astronauts showed an average decrease in bone mineral density of 2.1 percent in the shinbone -- one of the bones of the lower leg -- and a 1.3 percent decrease in bone strength. Nine astronauts did not experience any restoration of bone mineral density after spaceflight, experiencing permanent loss.

"We know that astronauts experience bone loss on long space flights. What's new about this study is that we followed astronauts for one year after their spacewalk to understand whether and how bone recovers," said University of Calgary professor Leigh Gabel, a sports scientist who is the lead author of the study, which was published this week in the journal Scientific Report.

"Astronauts experienced significant bone loss during their six-month space flight -- a loss we expect to occur in older adults over two decades on Earth, and they only recovered about half of that loss after a year back on Earth," said Dr. Gabel, as quoted by Reuters.

Bone loss occurs because the bones that normally carry the load on earth do not carry the weight in space. Space agencies need to step up preventive measures -- exercise and nutrition practices -- to help prevent bone loss, Gabel said.

"During spaceflight, the fine bone structure thins, and eventually some bone shafts are cut off from each other. Once the astronaut returns to earth, the remaining bone joints can thicken and strengthen, but the bones that were severed in space cannot be rebuilt, so the whole the astronaut's bone structure changes permanently," Gabel said.

The astronauts studied were flying on the space station since seven years ago. The study did not state their nationalities but they were from the US space agency NASA, the Canadian Space Agency, the European Space Agency and the Japanese Aerospace Exploration Agency.

Space travel poses various challenges to the human body. This is a major concern for space agencies as they plan new explorations. For example, NASA is planning to send astronauts back to the moon, as early as 2025. That could be the start of future astronaut missions to Mars or a long stay on the lunar surface.

"Microgravity affects many body systems, including muscles and bones," says Gabel.

The cardiovascular system also undergoes many changes. Without gravity pulling blood to the legs, astronauts experience a fluid shift that causes more blood to collect in the upper body. This condition can affect the cardiovascular system and vision.

"Radiation is also a big health concern for astronauts because the further they travel from Earth, the greater their exposure to solar radiation and the increased risk of cancer," Gabel said.

The study showed that longer space missions resulted in more bone loss and a lower chance of bone recovery afterward.

Exercise in space flight -- resistance training on the space station -- has been shown to be important for preventing muscle and bone loss. Astronauts who did more weight lifting than they would normally do on Earth were found to be more likely to recover bone after a mission.

"We still don't know much about how microgravity affects human health, especially on space missions longer than six months, and about the long-term health consequences," Gabel said. "We really hope that bone loss will eventually stabilize on longer missions, that astronauts will stop experiencing bone loss, but we don't know."