A drug that prevents bone loss could permit astronauts to make long journeys in space, according to results from a study of spinal injury patients.

The two biggest persistent health problems in space flight are radiation exposure and bone loss, says Jay Shapiro, a bone researcher at the Uniformed Services University in Bethesda, Maryland. “They have to be solved before we launch a manned Mars mission.”

Shapiro leads a team that has studied the effects of zoledronate in spinal injury patients over the course of a year. The drug is normally used to prevent secondary bone tumours developing in cancer patients, and has shown early promise in retarding the effects of the bone-wasting disease osteoporosis.

But spinal injury patients provide a much better model than those with osteoporosis for the weightless conditions in space, says Shapiro, because such patients lose bone at a similar rate to astronauts. “If grandma has osteoporosis, she loses about 2-3% of her bone mass every decade. Astronauts lose about 2% every month, and exercise has little impact on that,” he says.

In the study, eight patients who did not take the drug lost 16-18% of their femur bone mass over a year, while seven patients using the drug lost only 6%. “The drug significantly reduced bone loss,” says Shapiro. “It’s very much a first step, but it seems the most reasonable drug to use to allow trips to Mars.”

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