Diet and nitrogen metabolism during spaceflight on the shuttle.
Stein, T. P., M. J. Leskiw, and M. D. Schluter.
Department of Surgery, University of Medicine and Dentistry of New
Jersey, School of Osteopathic Medicine, Stratford, NJ, 08084
APStracts 2:0504A, 1995.
Human space flight is associated with a loss of body protein. To
investigate this problem, dietary intake, nitrogen balance, the whole
body protein and fibrinogen protein synthesis rates were measured on
the crews of two Life Sciences Space Shuttle missions before, during
and after spaceflight . The first mission, Space Life Sciences 1
(SLS-1) lasted 9.5 days and the second, Space Life Sciences 2 (SLS-2)
lasted 15 days. The 15N glycine method was used for the protein
synthesis measurements. Results: Data are means + SEM with the number
of subjects in parentheses. (i) There was a rapid decline in weight
for the first five days and then the body weight appeared to
stabilize. (ii) Preflight the mean energy intake was 39.0 + 2.5 (10)
kcal/kg/d. There was a sharp drop in dietary intake on flight day 1
with recovery by the second day and then energy intake was constant
at 30.4 + 1.5 (12) kcal/kg/d for the remainder of the flight period
(p<0.05). (iii) Nitrogen retention was decreased during flight
with the magnitude of the decrease lessening towards the end of the
mission. The daily mean N balance changed from 58 + 9 (9) mg/kg/d
preflight to 16 + 3 (11) mg N/kg/d, p<0.05) inflight
corresponding to a loss of about 1 kg of lean body mass over 14 days.
(iv) Whole body protein synthesis was increased early inflight and on
recovery as was fibrinogen synthesis. Conclusions: (i) The rapid
readjustment and stabilization of energy intake and the improved
nitrogen retention with increasing flight duration are consistent
with a rapid metabolic accommodation to the novel environment. (ii)
The increased protein turnover indicate that a metabolic stress
response is an important factor in this adjustment process.
Received 2 February 1995; accepted in final form 18 September
1995.
APS Manuscript Number A120-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95