02 Jul Iron Stores and Bone Loss During Long-Duration Space Flight on the International Space Station
Nutritionist, Manager for Nutritional Biochemistry
Biomedical Research and Environmental Sciences Division
NASA Johnson Space Center
Houston, TX 77058
Iron status and its relations with oxidative damage and bone loss during long-duration space flight on the International Space Station
MedicalResearch.com: What are the main findings of the study?
Dr. Smith: The key finding from this study is that the increase in iron stores during spaceflight is related to both oxidative damage and bone loss. Iron stores increase in microgravity because blood volume decreases during the initial weeks of spaceflight. The iron in excess red blood cells is not reused by new RBCs during spaceflight and is stored. This increase in iron stores was associated with increased indices of oxidative damage, and furthermore, the magnitude of the increase in iron stores during flight (i.e., the area under the curve) was correlated with bone mineral density loss. That is, the greater the iron stores, the more bone loss.
MedicalResearch.com: Were any of the findings unexpected?
Dr. Smith: We did not expect to see virtually identical temporal responses between the increase in iron stores and oxidative damage to DNA early in flight. Similar relationships between iron and oxidative damage have been shown by other investigators to occur in Earth-based models, but spaceflight provides a unique environment and opportunity for research. Among the unique factors are the fact that astronauts are generally very healthy, and that the changes observed due to the environment happen rather quickly. Thus, we observed these changes in a matter of months, whereas similar research on Earth would take years.
Dr. Smith: As with many nutrients, although not getting enough iron is a common concern, getting too much is also cause for concern. Our study, among other recent papers, shows that increased iron stores can be problematic, and that these effects are seen well below what are typically considered toxic levels of iron. In the broader context, this paper highlights that research on board the International Space Station has implications far beyond NASA for the general medical and scientific communities, and the general population.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Smith: With regard to spaceflight, further research is required to better understand iron metabolism in astronauts on long-duration missions, and how these changes are related to other health concerns of space travel, including radiation, cancer risk, and immune dysfunction. The health effects of iron have significant implications for the spaceflight food system, which provides about 3 times as much iron intake as the Earth-based recommended dietary allowance calls for. On missions to other planets or celestial bodies, this could cause or contribute to significant health issues.
In general, these findings broaden the growing database built by studies highlighting the association of increased iron stores with disease incidence. We report implications for oxidative damage and bone health, but existing literature suggests a much broader effect. This requires further study.
Iron status and its relations with oxidative damage and bone loss during long-duration space flight on the International Space Station.
Zwart SR, Morgan JL, Smith SM.
Division of Space Life Sciences, Universities Space Research Association, Houston, TX and Human Health and Performance Directorate, National Aeronautics and Space Administration Lyndon B Johnson Space Center, Houston, TX.
Am J Clin Nutr. 2013 Jul;98(1):217-23.
Epub 2013 May 29.