PRACTICAL AND CLINICAL NUTRITIONAL CONCERNS DURING SPACEFLIGHT

Experience with space exploration to date has raised more questions re garding nutritional requirements for astronauts than it has answered. As mission lengths continue to increase, nutrient imbalances due to al terations in intake, dietary requirements, bioavailability, or excreti on, may become more important. Factors adversely affecting intake incl ude those as straightforward as stress and as complex as space-adaptat ion syndrome. Metabolic alterations induced by shifts in fluid and ele ctrolyte balance, neuroendocrine function, and changes in hepatic prot ein synthesis and skeletal muscle type that result in nutrient partiti oning to different biochemical pathways may also affect dietary requir ements. Food processing effects on nutrient stability and digestibilit y, which apply to limited quantities of our usual diet on Earth, may b ecome more important for diets that contain little fresh food during e xtended-length missions. Whereas nutrient and water recycling through ecosystems is taken for granted on Earth, specific effects of trace co ntaminant accumulation will require greater attention for prolonged sp ace flights. Human factors, esthetics, and user-friendly operations wi ll be necessary to facilitate the psychological as well as physiologic al health of the astronauts.