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

INTRODUCTION

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).

DISCUSSION

These changes are similar to some of those observed during spaceflight, and further document the utility of bed rest as a model of spaceflight.