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fluid and electrolyte nutritionStudies of fluid and electrolyte homeostasis have been completed since the early human space flight programs, with comprehensive research completed on the Spacelab Life Sciences missions SLS-1 and SLS-2 flights, and more recently on the Mir 18 mission. This work documented the known shifts in fluids, the decrease in total blood volume, and indications of reduced thirst. Data from these flights was used to evaluate the nutritional needs for water, sodium, and potassium. Interpretations of the data are confounded by the inadequate energy intakes routinely observed during space flight. This in turn results in reduced fluid intake, as food provides approximately 70% water intake. Subsequently, body weight, lean body mass, total body water, and total body potassium may decrease. Given these issues, there is evidence to support a minimum required water intake of 2 L per day. Data from previous Shuttle flights indicated that water intake is 2285 +/- 715 ml/day (mean +/- SD, n=26). There are no indications that sodium intake or homeostasis is compromised during space flight. The normal or low aldosterone and urinary sodium levels suggest adequate sodium intake (4047 +/- 902 mg/day, n=26). Because excessive sodium intake is associated with hypercalciuria, the recommended maximum amount of sodium intake during flight is 3500 mg/day (i.e., similar to the Recommended Dietary Allowance, RDA). Potassium metabolism appears to be more complex. Data indicate loss of body potassium related to muscle atrophy and low dietary intake (2407 +/- 548 mg/day, n=26). Although possibly related to measurement error, the elevations in blood potassium suggest alterations in potassium homeostasis. The space RDA for minimum potassium intake is 3500 mg/day. With the documented inadequate intakes, efforts are being made to increase dietary consumption of potassium.
Document ID
20000020625
Document Type
Conference Paper
Authors
Lane, Helen W.
(NASA Johnson Space Center Houston, TX United States)
Smith, Scott M.
(NASA Johnson Space Center Houston, TX United States)
Leach, Carolyn S.
(NASA Johnson Space Center Houston, TX United States)
Rice, Barbara L.
(Enterprise Advisory Services, Inc. Houston, TX United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Publication Information
Publication: Proceedings of the First Biennial Space Biomedical Investigators' Workshop
Subject Category
Man/System Technology and Life Support
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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IDRelationTitle20000020485Analytic PrimaryProceedings of the First Biennial Space Biomedical Investigators' Workshop