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Effects of 21 days of bed rest, with or without artificial gravity, on nutritional status of humans

¹Universities Space Research Association, Houston; ²Enterprise Advisory Services, Inc., Houston; ³University of Texas Medical Branch, Galveston, Texas; ⁴Department of Chemistry, Indiana University-Purdue University Fort Wayne, Fort Wayne, Indiana; ⁵JES Tech, Houston; ⁶Human Adaptation and Countermeasures Division, National Aeronautics and Space Administration Johnson Space Center, Houston, Texas; and ⁷German Aerospace Center-Institute of Aerospace Medicine, Linder Hoehe, Cologne, Germany

Submitted 19 August 2008 ; accepted in final form 1 December 2008

Spaceflight and bed rest models of microgravity have profound effects on physiological systems, including the cardiovascular, musculoskeletal, and immune systems. These effects can be exacerbated by suboptimal nutrient status, and therefore it is critical to monitor nutritional status when evaluating countermeasures to mitigate negative effects of spaceflight. As part of a larger study to investigate the usefulness of artificial gravity as a countermeasure for musculoskeletal and cardiovascular deficits during bed rest, we tested the hypothesis that artificial gravity would have an effect on some aspects of nutritional status. Dietary intake was recorded daily before, during, and after 21 days of bed rest with artificial gravity (n = 8) or bed rest alone (n = 7). We examined body composition, hematology, general blood chemistry, markers of oxidative damage, and blood levels of selected vitamins and minerals before, during, and after the bed rest period. Several indicators of vitamin status changed in response to diet changes: serum - and -tocopherol and urinary 4-pyridoxic acid decreased (P < 0.001) and plasma β-carotene increased (P < 0.001) in both groups during bed rest compared with before bed rest. A decrease in hematocrit (P < 0.001) after bed rest was accompanied by a decrease in transferrin (P < 0.001), but transferrin receptors were not changed. These data provide evidence that artificial gravity itself does not negatively affect nutritional status during bed rest. Likewise, artificial gravity has no protective effect on nutritional status during bed rest.

microgravity; countermeasure; vitamin E; β-carotene; vitamin B₆

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