Nutritionists have some advice for astronauts worried about bone loss: Eat more fish -- and while you're at it, skip the salt.
Studies show strong ties between how much fish astronauts eat while in orbit and the amount of bone they were able to preserve, says NASA nutritionist Scott Smith, with the Johnson Space Center in Houston.
Astronauts typically lose between 1 to 1.5 percent of their bone mass per month in orbit. A postmenopausal woman, by comparison, loses that amount of bone in a year. On Earth, the condition often leads to osteoporosis, which leaves bones susceptible to fractures and breaks.
Whether a diet rich in fish can help mitigate bone loss for the terrestrial-bound has not been determined, but Smith finds it highly likely.
"When we try to apply what we learn in spaceflight on the ground, it's almost like looking at time-lapse photography. It's so accelerated. In a six-month station crewmember, you can see what would take six years on the ground," Smith told Discovery News.
"If we can better understand the changes in bone in spaceflight and how to counteract with something as simple as diet, the implications for the rest of us here on Earth are pretty remarkable," he added.
Smith and colleagues credit the omega-3 fatty acids present in some fish with helping to stem bone loss. A second study on subjects confined to bed rest -- intended to simulate the muscle atrophy and other conditions astronauts experience in weightlessness -- found similar results.
"It was one of those jump-out-of-your-chair moments," Smith said. "The more omega-3 fatty acids consumed, the lower the rate of bone breakdown in those subjects.
A related study is under way to determine the role of salt in bone loss, which is particularly relevant because the space station's pantry is stocked with foods very high in sodium.
"It's hard to make low-sodium food because there are no freezers," Smith said. "Salt is a good preservative. And it generally makes things taste better."
The research was presented at the American Astronautical Society meeting in Cape Canaveral, Fla., last week. It also appears in the Journal of Bone and Mineral Research.