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Space Travel Increases Some Health Risks

Interim Mir Science Results Symposium

November 4, 1998: Almost a half century after the first human explored space, doctors are still exploring how the human body reacts to space.

The latest round of results from those proddings, samplings, and probings were discussed today at the opening session of the third interim science results symposium for the Shuttle-Mir program.

Right: Nurse Dee O'Hara draws blood from John Glenn before his Feb. 20, 1962, launch on a three-orbit mission. O'Hara later managed the Human Research Facility at NASA's Ames Research Center.

"When we planned the first Space Shuttle-Mir docking mission, we saw great potential for science experiments," said Joel Kearns, manager of the Microgravity Research Program Office at Marshall Space Flight Center, as he spoke at the opening session. During 1996-98, NASA used the Shuttle-Mir program to gain experience in space station operations and how best to conduct experiments under a range of conditions.

"Now we look back with great happiness" at the data coming from the program and "we know how much we needed to know to get ready for the International Space Station."

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High on the list of experiments is the same concern that doctors had when Yuri Gagarin became the first human into space on April 12, 1961: How do the human body and its functions change when gravity is effectively removed? Gravity still holds the space traveler and spacecraft in orbit around the Earth, but the net effect is often called zero-g or microgravity.

Gagarin, a Marine Corps pilot named John Glenn, and dozens of other people since quickly demonstrated that space travel poses no immediate threat to your health. But scientists know that serious changes can result from subtle effects, so medical scientists have asked ever more detailed questions of the human body in space.

For example, what is the risk of getting a kidney stone as a result of space travel since the body quickly dumps a lot of fluid when gravity is no longer drawing blood down into the legs and the elastic vessels squeeze it upward? The population at greatest risk on Earth is people aged 35 to 50 - precisely the age span of most U.S. astronauts.

"The greatest risk appears early in flight [in 3 to 5 days] and immediately thereafter," said Dr. Robert Pietrzyk of Krug Life Sciences at Johnson Space Center. Pietrzyk and other researchers assayed urine samples passed by astronauts before flight, during their stays in space, and several times after the return to Earth.

Left: Glenn is checked over after returning to Earth. Simple things like changes in heart rate and blood pressure when sitting up or standing are still important markers in studying how the body adjusts in going from weightless in space to weighted back on Earth.

They were looking for various compounds of calcium, a metal important to the structure of bones and to the biochemical mechanisms that make muscles contract. Certain calcium compounds can form kidney stones - crystals growing in urine rich in the right chemicals - that block the kidneys or the bladder.

In addition to increased risk during flight, Pietrzyk noted that the risk can increase after landing, as noted in increased calcium output as the body readjusts to gravity. To date, though, only three astronauts have developed kidney stones, two preflight and one post-flight. None has appeared in flight.

Another important marker is the quantity of proteins lost, said Dr. Peter Stein of the University of Medicine and Dentistry of New Jersey.

Proteins are the basic machinery of the body, he explained, an important to muscle function, cell structure, immune responses - in fact, he said that the body has no spare proteins.

So, the loss of proteins - as measured by certain markers in urine and blood samples - is of great concern. One of the effects he has measured is a 45 percent decrease in protein synthesis as compared to a 15 to 20 percent decrease expected from bed rest studies.

"This looks very odd," he said, "it looks too high."

After checking several related factors, he said that it appears that one of the keys is the individual's energy balance in space where the energy demand on a person at work can sometimes be less than on a person sitting upright on Earth.

Web Links

Shuttle-Mir research Including space biology, materials sciences, and other fields.

Shuttle-Mir Increment 6 and Increment 7 activities and science described.

Microgravity Program Office at Marshall Space Flight Center

First phase of Shuttle-Mir science harvest to be discussed - Interim science results symposium planned - story posted Nov. 3

"It's not the intake, it's the energy balance that counts," he explained. "Are you taking in enough protein to meet your needs? ... The decrease in energy intake explains much of the decrease in protein synthesis."

Unraveling the problem will take more detailed study partly because of the human body's remarkable ability to adjust to sharp changes in food.

Tomorrow the symposium covers what space life is like if you happen to be the space station: vehicle dynamics and the external environment are on the menu.

More web links

More Space Science Headlines - NASA research on the web

Microgravity Program Office at Marshall Space Flight Center

Life and Microgravity programmatic information from NASA headquarters.


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Author: Dave Dooling
Curator: Bryan Walls
NASA Official: John M. Horack