| Bone loss due to microgravity other than senile osteoporosis is a complex changing process in which local mechanical signal transduction plays a leading role and subjected to multiple levels of regulation. It is a kind of special disuse osteoporosis and secondary osteoporosis. The persistent bone mineral loss in long-term microgravity flying is one of the main serious physiological reactions to astronauts, which is also the main obstacle in long-term space staying and planetary exploration. The countermeasures typically fall into one of four general categories - physical, nutritional, pharmacological and cytokine & gene therapy. The physical countermeasures (such as resistive exercise, vibration and artificial gravity) have been studied more intensively than other countermeasures. The impacts of vitamin, mineral substance, protein and omega-3 fatty acid to bone loss in (simulated) microgravity environment as nutritional countermeasures have been summarized but the reference space flight intakes of the above nutrients are yet to be standardized. Bisphosphonates as a means of inhibiting bone resorption have been widely recognized, other medicines (such as selective estrogen, testosterone, parathyroid hormone, leptin and statins) still need to be explored in vivo. Cytokine & gene therapy still confine to cell experiments so far. An advanced resistive exercise device (ARED) combined with nutrition (partly also combined with bisphosphonates) is currently recognized as effective measures against bone loss in space flight. |