Microgravity inhibits intestinal calcium absorption as shown by a stable strontium test
Article first published online: 7 JUL 2008
European Journal of Clinical Investigation
Volume 30, Issue 12, pages 1036–1043, December 2000
How to Cite
Zittermann, A., Heer, M., Caillot-Augusso, A., Rettberg, P., Scheld, K., Drummer, C., Alexandre, C., Horneck, G., Vorobiev, D. and Stehle, P. (2000), Microgravity inhibits intestinal calcium absorption as shown by a stable strontium test. European Journal of Clinical Investigation, 30: 1036–1043. doi: 10.1046/j.1365-2362.2000.00682.x
- Issue published online: 7 JUL 2008
- Article first published online: 7 JUL 2008
- Received 30 July 1999; accepted 19 March 2000
- Bone resorption;
- calcium absorption;
- strontium test;
- vitamin D
Little is known about the onset and degree of biochemical and functional alterations in calcium metabolism during microgravity.
To evaluate the effect of microgravity on intestinal calcium absorption and calcium-regulating hormones under metabolic ward conditions.
Fractional calcium absorption (Fc240 in percentage of dose administered) was determined pre-flight, in-flight and post-flight, by use of a stable strontium test in one cosmonaut who spent 20 days in space. Moreover, a sequence of blood samples was collected for the determination of serum parathyroid hormone (PTH), 25-hydroxyvitamin D, calcitriol and serum C-telopeptide (CTx, biomarker of bone resorption) levels. During all periods of data collection, calcium intake was held constant at a minimum level of 1·000 mg day−1 and a daily supplement of 16·6 µg vitamin D2 was given. Personal ultraviolet (UV) light exposure was measured during the whole mission using a biologically weighting UV dosimeter.
Fc240 was markedly reduced on flight day 19 (4·4%) as compared to pre-flight and post-flight data (13·4% and 17·2%, respectively). Serum calcitriol levels fell from 40·6 pg mL−1 (mean pre-flight level) to 1·3 pg mL−1 on flight day 18 and returned into the normal range after recovery. Serum CTx increased during the flight, while serum PTH and 25-hydroxyvitamin D levels did not change significantly.
Intestinal calcium absorption can be diminished after only three weeks of microgravity. Changes are associated with a severe suppression of circulating calcitriol levels, but are independent of exogenous vitamin D supply and serum PTH levels.