The weightlessness of space flight and weightlessness effects of bed rest both can trigger a type of inflammatory immune response that speeds bone loss and may lead to osteoporosis. The immune inflammatory factor, called NFkB, can weaken muscle and bone. Researchers analyzed four types of studies: short-flight space shuttle crews, cell culture, bed rest, and long-term space station crews.
In astronauts returning from short space-shuttle flights, researchers drew blood at landing and found NFkB activity was elevated and remained high for two weeks, evidence that the body adapts to zero gravity through inflammatory processes.
In the cell culture studies, omega-3 fatty acids slowed NFkB activity.
Bed rest mimics some of the effects of weightlessness. In one study, doctors found that, among people bedridden for 60 days, those who consumed less omega-3 fatty acids had more bone loss compared to those who consumed more omega-3s.
In the final study, researchers measured bone mineral loss in astronauts who were in space for four to six months. Those who consumed less fish during flight lost more bone mineral than those who ate more fish.