Nutritional status assessment before, during, and after long-duration head-down bed rest.

Nutritional Biochemistry Laboratory, Human Adaptation and Countermeasures Division, NASA Johnson Space Center, Houston, TX 77058, USA.
Aviation Space and Environmental Medicine (Impact Factor: 0.88). 06/2009; 80(5 Suppl):A15-22.
Source: PubMed


Bed rest is a valuable ground-based model for many of the physiological changes that are associated with spaceflight. Nutritional changes during and after 60 or 90 d of head-down bed rest were evaluated.
A total of 13 subjects (8 men, 5 women; ages 26-54 yr) participated in either 60 or 90 d of bed rest. Blood and urine were collected twice before bed rest and about once per month during bed rest. Samples were stored frozen and batch analyzed. Data were analyzed using repeated-measures analysis of variance.
During bed rest, markers of bone resorption (such as N-telopeptide excretion, P < 0.001) increased and serum concentration of parathyroid hormone decreased (P < 0.001). Also, oxidative damage markers such as superoxide dismutase increased (P < 0.05), and after 90 d of bed rest, total antioxidant capacity decreased (P < 0.05). During bed rest, iron status indices showed patterns of increased iron stores with a decreased concentration of transferrin receptors (P < 0.01).
These changes are similar to some of those observed during spaceflight, and further document the utility of bed rest as a model of spaceflight.

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    • ", Quidel, Santa Clara, CA; HP, MicroVue TM Helical Peptide EIA, Quidel), as described previously (Smith et al. 1999, 2003, 2004b, 2005a,b, 2008, 2009b, 2014). Serum total calcium and urinary calcium were determined by atomic absorption spectrophotometry (PerkinElmer, Waltham, MA, 1.86% within-and 2.52% between-assay CVs, CAP proficiency testing) (Smith et al. 2005a,b, 2008, 2009b, 2012b,c, 2014; Zwart et al. 2009b, 2011a), and wholeblood ionized calcium (<1% CV) was determined using a portable analyzer (i-STAT â 1 Analyzer, i-STAT, East Windsor, NJ; between-assay CV for ionized Ca = 1.15%) (Smith et al. 1997, 2004a). Urinary creatinine (5.1% CV) was analyzed using a colorimetric technique on an ACE Alera â analyzer (Alfa Wassermann, West Caldwell, NJ, 2.99% within-and 3.30% between-assay CV, CAP proficiency testing) (Smith et al. 2005a,b, 2008, 2009b, 2012b, 2014; Zwart et al. 2009b, 2011a). "
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