When scientists learned that space travel causes bone loss in crew members, they began looking for ways to prevent this bone loss, which can lead to osteoporosis. Years of space research has helped improve our understanding of bone health and osteoporosis.
The pull of gravity on Earth provides the benefit of weight-bearing activities in keeping bones strong and healthy. Weight-bearing activities, such as walking or dancing, cause our bones to support the weight of our bodies. In children and teens, weight-bearing activities help build strong bones and increase bone density in growing bone.
High-impact activities such as jumping are particularly effective. In adults, these types of activities help keep the bones in our legs, hips and lower spine strong. They also help prevent or slow the loss of bone mass and density as we grow older.
Weightlessness due to “zero gravity” occurs during space travel or while living on the International Space Station (ISS). Crew members move about their space vehicle or ISS “floating” rather than standing on their feet and moving. This quickly causes a loss of bone density.
Space travelers can lose 1 to 2 percent of bone density a month. While in space, the amount of bone density a crew member loses in the hip during one month is about the same as what a postmenopausal woman loses in one year. This rapid bone loss is one of the single most important limitations to long-term space travel or residence in space. Space scientists have learned that the more time a person spends in space, the greater the loss of bone density.
Additionally, scientists have found that not all crew members have the same rate and amount of bone loss. This is similar to people on Earth and suggests the role that genetics play in developing osteoporosis. Some of this bone loss may be reversible when astronauts return to Earth.
Space studies on bone health continue throughout the country, especially at universities in partnership with the National Aeronautics and Space Administration. Researchers are looking at exercise, nutrition, hormones, drug treatment and other issues related to bone health.