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Vitamin D: Findings from Antarctic, Bed Rest, Houston, and ISSObtaining vitamin D is critical for space travelers because they lack ultraviolet light exposure and have an insufficient dietary supply of vitamin D. Despite the provision of 400 IU vitamin D supplements to International Space Station (ISS) early crewmembers, vitamin D status was consistently lower after flight than before flight, and in several crewmembers has decreased to levels considered clinically significant. Vitamin D has long been known to play a role in calcium metabolism, and more recently its non-calcitropic functions have been recognized. According to the results of several recent studies, functionally relevant measures indicate that the lower limit of serum 25-hydroxyvitamin D (a marker of vitamin D status) should be raised from the current 23 nmol/L to 80 nmol/L. The mean preflight serum 25-hydroxyvitamin D (25-OH vit D) for U.S. ISS crewmembers to date is 63 +/- 16 nmol/L, and after a 4- to 6-mo space flight it typically decreases 25-30% despite supplementation (400 IU/d). The sub-optimal pre- and postflight vitamin D status is an issue that needs to be addressed, to allow NASA to better define the appropriate amount of supplemental vitamin D to serve as a countermeasure against vitamin D deficiency in astronaut crews. A series of ground-based and flight studies in multiple models have been conducted, including Antarctica in winter months when UV-B radiation levels are essentially zero, bed rest where subjects are not exposed to UV-B radiation for 60-90 days, in free-living individuals in Houston, and in International Space Station crewmembers. In these studies, we looked at dose regimen and efficacy, compliance issues, as well as toxicity. Preliminary results from these studies will be presented. Together, the data from these studies will enable us to provide space crews with evidence-based recommendations for vitamin D supplementation. The findings also have implications for other persons with limited UV light exposure, including polar workers and the elderly.
Document ID
20090042673
Document Type
Conference Paper
Authors
Zwart, Sara R. (Universities Space Research Association Houston, TX, United States)
Locke, J. (Universities Space Research Association Houston, TX, United States)
Pierson, D. (Universities Space Research Association Houston, TX, United States)
Mehta, S. (Enterprise Advisory Services, Inc. Houston, TX, United States)
Bourbeau, Y. (Enterprise Advisory Services, Inc. Houston, TX, United States)
Parsons, H. (British Columbia Univ. Vancouver, British Columbia, Canada)
Smith, S. M. (NASA Johnson Space Center Houston, TX, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2009
Subject Category
Aerospace Medicine
Report/Patent Number
JSC-CN-19439
Meeting Information
HRP Investigators'' Workshop(Houston, TX)
Distribution Limits
Public
Copyright
Other