ISS Experiments: The Cause of Bone Loss in Space

By Erin Biba

By sampling the blood and urine of astronauts, scientists have discovered the reasons for rapid bone loss in microgravity.

NASA has been studying the effects of microgravity on the human body for almost as long as it has existed. On the International Space Station, their current research has focused on nutrition and how the human body is affected by different nutrients while in space. This particular research was difficult to do until 2006, because it requires sampling the blood and urine of astronauts (the samples need to be collected in space, stored and frozen, and returned to earth for analysis).

Photo credit: NASA

Before this particular study, astronauts gave samples before and after their mission. Scientists notices a significant change in several nutrients in their bodies. The current study aims to sample the astronaut’s nutrition periodically throughout their time on the Space Station in order to see how it changes over time.

One of the biggest discovery to come out of this area of study is how salt affects our bones. Astronauts experience accelerated osteoporosis while they’re floating around in microgravity. As a result, NASA has developed methods to assist them with combating the degradation of their bones and a return to normalcy once they hit solid ground. What researchers have discovered is that accelerated bone loss is tied directly into the strange fact that in space astronauts retain salt in their body--but not water.

Looking more closely at salinity in astronaut’s blood and urine, researchers were able to determine that sodium is retained (most likely in the skin) and changes the body’s acid balance, which in turn changes bone metabolism. In other words: the more salt in your body the more quickly your bones will deteriorate. Researchers believe this discovery will have big implications in the fight to treat the world’s osteoporosis problems (not to mention necessary adjustments to the dietary habits of space-goers).

You can read more about this experiment and other discoveries to come out of it here.