Space Bones - Osteoporosis

Weightlessness sure looks like a lot of fun, but prolonged exposure to zero-G in space can have some negative side effects - like osteoporosis and the weakening of human bones!

Everybody knows space is dangerous.

Some of the perils are obvious: hard vacuum, extreme cold, and unpredictable blasts of radiation from the Sun.

Other perils are less conspicuous. The effects of prolonged weightlessness on the human body, for example, can be slow and subtle - yet no less dangerous if astronauts fail to take proper precautions.

Weakening of the bones due to the progressive loss of bone mass is a particularly serious effect of extended spaceflight. Studies of cosmonauts and astronauts who spent many months on space station Mir revealed that space travellers can lose 1 to 2 percent of bone mass each month -- a loss doctors don't yet know how to prevent. "The magnitude of this effect has led NASA to consider bone loss an inherent risk of extended space flights," says Dr. Jay Shapiro, team leader for bone studies at the National Space Biomedical Research Institute.

Space travellers aren't the only ones who worry about bone loss. At least 10 million people suffer from bone loss in the U.S. and untold numbers worldwide -- it's called osteoporosis. Postmenopausal women are especially prone to osteoporosis, but most of us contract the disease as we age, including men. Researchers hope that solving the riddle of bone loss in space will reveal important clues about what causes osteoporosis right here on Earth.

Spacefarers typically experience bone loss in the lower halves of their bodies, particularly in the lumbar vertebrae and the leg bones. Diminishing bone mass also triggers a rise in calcium levels in the blood, which increases the risk of kidney stones.

Researchers suspect the root cause of bone loss in space is weightlessness.