title: Nutritional status assessment before, during, and after long-duration head-down bed rest.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  These changes are similar to some of those observed during spaceflight, and further document the utility of bed rest as a model of spaceflight.
authors.affiliation: Nutritional Biochemistry Laboratory, Human Adaptation and Countermeasures Division, NASA Johnson Space Center, Houston, TX 77058, USA.
authors.forename: Sara R
authors.initials: SR
authors.lastname: Zwart
authors.forename: Susan A Mathews
authors.initials: SA
authors.lastname: Oliver
authors.forename: J Vernell
authors.initials: JV
authors.lastname: Fesperman
authors.forename: Geeta
authors.initials: G
authors.lastname: Kala
authors.forename: Jane
authors.initials: J
authors.lastname: Krauhs
authors.forename: Karen
authors.initials: K
authors.lastname: Ericson
authors.forename: Scott M
authors.initials: SM
authors.lastname: Smith
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000975:Antioxidants / Q000378:metabolism; D001510:Bed Rest / Q000009:adverse effects*; D001774:Blood Chemical Analysis; D001862:Bone Resorption; D024042:Collagen Type I / Q000652:urine; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology; D006801:Humans; D007501:Iron / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D015596:Nutrition Assessment; D009752:Nutritional Status; D018384:Oxidative Stress; D010281:Parathyroid Hormone / Q000097:blood; D010455:Peptides / Q000652:urine; D011187:Posture; D011446:Prospective Studies; D013026:Space Flight; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors; D014815:Vitamins / Q000097:blood; D014893:Weightlessness / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D024042:Collagen Type I; D010281:Parathyroid Hormone; D010455:Peptides; D014815:Vitamins; C052929:collagen type I trimeric cross-linked peptide; D007501:Iron; D013482:Superoxide Dismutase