Calcium Supplementation Attenuates Disruptions in Calcium Homeostasis during Exercise.
Level 2 - randomized trial
Randomized controlled trial
PubMed 28248693 · doi:10.1249/MSS.0000000000001239
What was done
Fifty-one competitive male cyclists aged 18 to 45 years were randomized to take either 1000 mg chewable calcium or placebo 30 minutes before a simulated 35-km cycling time trial. Serum ionized calcium and parathyroid hormone were measured before and immediately after exercise. C-terminal telopeptide of type I collagen, a marker of bone resorption, was measured before and 30 minutes after exercise.
What was found
Serum ionized calcium decreased in both groups after exercise (calcium: 4.89 ± 0.16 to 4.76 ± 0.11 mg/dL; placebo: 4.92 ± 0.15 to 4.66 ± 0.22 mg/dL, both P ≤ 0.01), with a greater decrease in the placebo group (P = 0.03). Parathyroid hormone rose in both groups (calcium: 30.9 ± 13.0 to 79.7 ± 42.6 pg/mL; placebo: 37.1 ± 14.8 to 111.5 ± 49.4 pg/mL, both P ≤ 0.01), showing a nonsignificant attenuation by calcium (P = 0.07). C-terminal telopeptide of type I collagen increased in both groups (calcium: 0.35 ± 0.17 to 0.50 ± 0.21 ng/mL; placebo: 0.36 ± 0.13 to 0.54 ± 0.22 ng/mL, both P ≤ 0.01) with no treatment effect.
Why it matters
Pre-exercise calcium supplementation reduces the acute drop in ionized calcium during cycling, but ingestion 30 minutes prior does not prevent post-exercise rises in bone resorption markers.
Limits
The study tested only young-to-middle-aged competitive male cyclists during an acute cycling bout, limiting generalizability to females or other exercise types. Ingestion timing of 30 minutes pre-exercise may have been insufficient for optimal gut calcium absorption. Long-term bone density and clinical outcomes were not assessed.
Cited by
- supports Wendy Kohrt's research in Colorado showed that exercise onset causes blood calcium levels to drop, stimulating parathyroid hormone release and subsequent leaching of calcium from bones.