Related Experiment Videos
Microgravity inhibits intestinal calcium absorption as shown by a stable strontium test
A Zittermann1, M Heer, A Caillot-Augusso
1Institut für Ernährungswissenschaft, Universität Bonn, Germany. a.zittermann@uni-bonn.de
European Journal of Clinical Investigation
|December 21, 2000
Summary
Microgravity significantly reduces intestinal calcium absorption and calcitriol levels within three weeks. These changes occur despite adequate vitamin D intake and stable parathyroid hormone levels.
Area of Science:
- Space physiology
- Human metabolism
- Calcium regulation
Background:
- Limited understanding of calcium metabolism alterations in microgravity.
- Need to investigate biochemical and functional changes during spaceflight.
Purpose of the Study:
- To assess microgravity's impact on intestinal calcium absorption.
- To evaluate changes in calcium-regulating hormones during spaceflight.
Main Methods:
- Fractional calcium absorption (Fc240) measured pre-flight, in-flight, and post-flight using a stable strontium test.
- Serum levels of parathyroid hormone (PTH), 25-hydroxyvitamin D, calcitriol, and C-telopeptide (CTx) were monitored.
- Constant calcium intake (1,000 mg/day) and vitamin D2 supplementation were maintained.
Main Results:
- Fc240 decreased significantly by flight day 19 (4.4%) compared to pre-flight (13.4%) and post-flight (17.2%).
- Serum calcitriol levels dropped drastically from 40.6 pg/mL pre-flight to 1.3 pg/mL on flight day 18.
- Serum CTx increased during flight, while PTH and 25-hydroxyvitamin D showed no significant changes.
Conclusions:
- Microgravity diminishes intestinal calcium absorption within three weeks.
- This reduction is linked to severe suppression of calcitriol, independent of vitamin D or PTH levels.