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EXPERIMENT INFORMATION

Vitamin D Supplementation in an Antarctic Ground Analog of Space Flight: Study of Supplementation Protocol and Relationship to Immune System Function (ROI_Polar_II)
Principal Investigator
Research Area:
Metabolism and nutrition
Species Studied
Scientific Name: Homo sapiens Species: Human

Description
OBJECTIVES:
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 vitamin D supplements to International Space Station (ISS) crewmembers, vitamin D status is consistently lower after flight than before flight, and in several crewmembers, levels have decreased to concentrations considered clinically significant. Vitamin D has long been known to play a role in calcium metabolism, and more recently its non-calcitropic functions (functions not related to calcium metabolism, e.g., effects related to the incidence of cancer or diabetes) 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 standard of 25 nmol/L to 80 nmol/L. The mean preflight serum 25-hydroxyvitamin D for U.S. ISS crewmembers to date is 63 ± 16 nmol/L, and after a four- to six-month space flight mission it typically decreases 25-30% despite a supplementation of 400 International Units per day (IU/d). The suboptimal pre- and postflight vitamin D status is an issue that needs to be addressed so NASA can better define the appropriate amount of supplemental vitamin D to serve as a countermeasure against vitamin D deficiency in crewmembers. This is very important for long-duration crewmembers, and is critical for exploration class missions.

The environment in the Antarctic is quite unique. Seasonal changes in UV-B exposure are more extreme than in any other part of the world. The sun does not rise for 42 days during winter (June 1 – July 12), and the sun does not set for 60 days during the summer months (Nov 22 – Jan 20). During the Antarctic winter, scientists and visitors are typically isolated, and no fresh fruits or vegetables are available. As a result of close quarters and limited food choices throughout the year, most scientists at a particular research station have homogeneous food intakes and physical activities. Not only is Antarctic winter-over a good model for studying vitamin D metabolism because of the limited sunlight exposure, the Antarctic science station model has also been used successfully as a ground-based analog for space flight in studies of behavior, immune response, and latent virus reactivation. Antarctica was used in the proposed study to test the hypothesis that stress causes a reduction in the immune response. The Antarctic winter is similar to space flight with regard to the amount of ultraviolet radiation, which is zero during these months. This is an excellent environment for estimating how effective vitamin D supplements would be in space.

The investigators recently completed a ground-based investigation evaluating vitamin D supplementation efficacy during the winter months in Antarctica, when UV-B radiation levels are zero. A supplement of 2,000 IU/d raised serum 25-hydroxyvitamin D to acceptable levels, but compliance was an issue that needs to be overcome.

In this study, investigators studied whether a weekly dose of 10,000 IU vitamin D could be substituted for this daily 2000-IU dose, and investigated the effects of vitamin D supplementation on immune function in an environment known to suppress immune function. The main objective of this study was to determine if a weekly dose of vitamin D is just as effective as a daily dose to reach a desirable vitamin D status, and to maintain that level for the duration of the mission. Compliance is more difficult with a daily supplement, and a weekly supplement would be more desirable. A secondary objective was to determine if vitamin D supplementation improves immune function of subjects wintering over in Antarctica, a population known to have altered immune function.

The Specific Aims were:

1. To determine the time course and magnitude of changes in vitamin D status during wintering over in Antarctica, with or without vitamin D supplementation.
2. To determine other markers of bone and calcium metabolism (such as serum calcium, 1,25-dihydroxyvitamin D, and parathyroid hormone) before and after vitamin D supplementation to determine the effectiveness of supplementation.
3. To determine the relationships between vitamin D status and immune response. A polymerase chain reaction assay will be used to determine the reactivation patterns of varicella-zoster virus, a causative agent of chickenpox in children and shingles in adults.


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Publications
Zwart SR, Mehta SK, Ploutz-Snyder R, Bourbeau Y, Locke JP, Pierson DL, and Smith SM. Response to vitamin D supplementation during Antarctic winter is related to BMI, and supplementation can mitigate Epstein-Barr Virus Reactivation. The Journal of Nutrition. 2011. April 1; 141(4):692-7. [pubmed.gov]

Keywords
1,25-Dihydroxyvitamin D3
25-Hydroxyvitamin D3
Calcium, dietary
Vitamin D

Data Information
Data Availability
Archive is complete. Data sets are not publicly available but can be requested.
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Parameters
1,25-dihydroxyvitamin D
25-hydroxyvitamin D
Body weight
Bone Collagen Equivalents (nM BCE)
Bone-specific alkaline phosphatase (BSAP)
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Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
ROI 01/01/2002 12/31/2012 In Progress

Human Research Program (HRP) Human Research Roadmap (HRR) Information
Crew health and performance is critical to successful human exploration beyond low Earth orbit. The Human Research Program (HRP) investigates and mitigates the highest risks to human health and performance, providing essential countermeasures and technologies for human space exploration. Risks include physiological and performance effects from hazards such as radiation, altered gravity, and hostile environments, as well as unique challenges in medical support, human factors, and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify the approach and research activities planned to address these risks, which are assigned to specific Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.

The Human Research Roadmap is located at: https://humanresearchroadmap.nasa.gov/

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Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Pamela A. Bieri
Institutional Support
National Aeronautics and Space Administration (NASA)
Alternate Experiment Name
Polar II
Proposal Date
10/01/2006