title: Vitamin K status in spaceflight and ground-based models of spaceflight.
abstract: Bone loss is a well-documented change during and after long-duration spaceflight. Many types of countermeasures to bone loss have been proposed, including vitamin K supplementation. The objective of this series of studies was to measure change in vitamin K status in response to microgravity under a variety of spaceflight and spaceflight analog (model) conditions, including long-duration spaceflight studies (n = 15), three bed rest studies (n = 15, 49, and 24), and a 14-day saturation dive (n = 6). In crew members who flew 2-6 months on the International Space Station, in-flight and postflight plasma phylloquinone concentrations were unchanged from the preflight mean. Consistent with this finding, urinary γ-carboxyglutamic acid (GLA), a measure of vitamin K-dependent protein turnover, did not change in response to flight. Serum undercarboxylated osteocalcin (%ucOC), a measure of vitamin K function, was generally unchanged in response to flight. Spaceflight findings were corroborated by findings of no changes in phylloquinone, urinary GLA, or %ucOC during or after bed rest in three separate bed rest studies (21-90 days in duration) or after a 14-day saturation dive. The data presented here do not support either a need for vitamin K supplementation during spaceflight or the suggestion of using vitamin K as a bone loss countermeasure in spaceflight.
authors.affiliation: Division of Space Life Sciences, Universities Space Research Association, Houston, TX, USA.
authors.forename: Sara R
authors.initials: SR
authors.lastname: Zwart
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Booth
authors.forename: James W
authors.initials: JW
authors.lastname: Peterson
authors.forename: Zuwei
authors.initials: Z
authors.lastname: Wang
authors.forename: Scott M
authors.initials: SM
authors.lastname: Smith
mesh_terms: D001510:Bed Rest; D015415:Biomarkers / Q000097:blood; D015444:Exercise / Q000502:physiology; D005260:Female; D018470:Gravity, Altered; D006801:Humans; D008297:Male; D013026:Space Flight; D014481:United States; D018557:United States National Aeronautics and Space Administration; D014812:Vitamin K / Q000097:blood*
chemical_list: D015415:Biomarkers; D014812:Vitamin K