Sherk Vanessa D, Wherry Sarah J, Barry Daniel W, Shea Karen L, Wolfe Pamela, Kohrt Wendy M
1Division of Geriatric Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO; and 2Department of Preventative Medicine and Biostatistics, University of Colorado Anschutz Medical Campus, Aurora, CO.
Med Sci Sports Exerc. 2017 Jul;49(7):1437-1442. doi: 10.1249/MSS.0000000000001239.
An exercise-induced decrease in serum ionized calcium (iCa) is thought to trigger an increase in parathyroid hormone (PTH), which can stimulate bone resorption.
The purpose of this study was to determine whether taking a chewable calcium (Ca) supplement 30 min before exercise mitigates disruptions in Ca homeostasis and bone resorption in competitive male cyclists.
Fifty-one men (18 to 45 yr old) were randomized to take either 1000 mg Ca (CA) or placebo (PL) 30 min before a simulated 35-km cycling time trial. Serum iCa and PTH were measured before and immediately after exercise and a marker of bone resorption (C-terminal telopeptide of type I collagen) was measured before and 30 min after exercise.
Serum iCa decreased in both groups from before to after exercise (mean ± SD, CA = 4.89 ± 0.16 to 4.76 ± 0.11 mg·dL, PL = 4.92 ± 0.15 to 4.66 ± 0.22 mg·dL, both P ≤ 0.01); the decrease was greater (P = 0.03) in the PL group. There was a nonsignificant (P = 0.07) attenuation of the increase in PTH by Ca supplementation (CA = 30.9 ± 13.0 to 79.7 ± 42.6 pg·mL, PL = 37.1 ± 14.8 to 111.5 ± 49.4 pg·mL, both P ≤ 0.01), but no effect of Ca on the change in C-terminal telopeptide of type I collagen, which increased in both groups (CA = 0.35 ± 0.17 to 0.50 ± 0.21 ng·mL, PL = 0.36 ± 0.13 to 0.54 ± 0.22 ng·mL, both P ≤ 0.01).
It is possible that ingesting Ca only 30 min before exercise was not a sufficient time interval to optimize gut Ca availability during exercise. Further studies will be needed to determine whether adequate Ca supplementation before and/or during exercise can fully mitigate the exercise-induced decrease in serum iCa and increases in PTH and bone resorption.
运动引起的血清离子钙（iCa）降低被认为会引发甲状旁腺激素（PTH）升高，进而刺激骨吸收。
本研究旨在确定在运动前30分钟服用咀嚼型钙（Ca）补充剂是否能减轻竞技男性自行车运动员钙稳态和骨吸收的破坏。
51名男性（18至45岁）被随机分为两组，在模拟35公里自行车计时赛开始前30分钟，一组服用1000毫克钙（CA组），另一组服用安慰剂（PL组）。在运动前和运动后立即测量血清iCa和PTH，并在运动前和运动后30分钟测量骨吸收标志物（I型胶原C末端肽）。
两组运动后血清iCa均下降（平均值±标准差，CA组=4.89±0.16至4.76±0.11毫克·分升，PL组=4.92±0.15至4.66±0.22毫克·分升，P均≤0.01）；PL组下降幅度更大（P = 0.03）。补充钙对PTH升高有不显著的减轻作用（P = 0.07）（CA组=30.9±13.0至79.7±42.6皮克·毫升，PL组=37.1±14.8至111.5±49.4皮克·毫升，P均≤0.01），但钙对I型胶原C末端肽的变化无影响，两组该指标均升高（CA组=0.35±0.17至0.50±0.21纳克·毫升，PL组=0.36±0.13至0.54±0.22纳克·毫升，P均≤0.01）。
运动前仅30分钟摄入钙，这个时间间隔可能不足以在运动期间优化肠道钙的可利用性。需要进一步研究以确定运动前和/或运动期间充分补充钙是否能完全减轻运动引起的血清iCa降低以及PTH和骨吸收增加。
