Department of Kinesiology, Missouri Southern State University, Joplin, MO.
Children's Hospital Oakland Research Institute, Oakland, CA.
Am J Clin Nutr. 2019 Jan 1;109(1):197-206. doi: 10.1093/ajcn/nqy233.
Low calcium intake during pregnancy may cause maternal skeletal calcium mobilization to meet fetal needs. The Recommended Dietary Allowance (RDA) for calcium in nonpregnant, pregnant, or lactating women aged 19-50 y is 1000 mg/d; most women in the United States report consuming 60-80% of the calcium RDA. An insufficient calcium intake could increase maternal bone loss during pregnancy and reduce bone recovery postpartum.
The aim of this study was to determine the effect of maternal calcium supplementation on peripheral cortical and trabecular bone loss during pregnancy and bone gain postpartum.
A total of 64 women were enrolled in the study at 16 wk of gestation and randomly assigned to receive 1000 mg Ca/d or placebo for the remainder of the pregnancy. Measurements were performed at 16, 26, and 36 wk of pregnancy and at 4 and 12 mo postpartum for serum 25-hydroxyvitamin D and markers of bone turnover. Trabecular and cortical bone mineral density (BMD) and content were assessed at the tibia and radius by peripheral quantitative computed tomography.
Mean ± SD daily calcium intake at baseline was 733 ± 350 mg; only 25% of the women met the RDA. Thirty women (47% of those enrolled) remained in the study at 12 mo postpartum. After controlling for baseline bone value, serum 25-hydroxyvitamin D concentrations, length of breastfeeding, and body mass index, the calcium group had significantly greater increases in radial total BMD (P = 0.02) and tibial cortical BMD (P = 0.03) at 12 mo postpartum than the placebo group. Trabecular and total BMD at the tibia trended toward higher values (P < 0.06) in the calcium group than in the placebo group in the same models.
These data show that supplemental calcium provided during pregnancy may improve bone recovery postpartum in women consuming a typical US diet. A larger study is warranted to solidify the conclusions. This trial was registered at clinicaltrials.gov as NCT01145573.
孕期钙摄入量低可能导致母体骨骼中的钙动员以满足胎儿的需求。非妊娠、妊娠或哺乳期 19-50 岁女性的推荐膳食允许量（RDA）为 1000 毫克/天；大多数美国女性报告的钙 RDA 摄入量为 60-80%。钙摄入不足可能会增加孕期母体骨丢失，并减少产后骨恢复。
本研究旨在确定母体补钙对孕期外周皮质和小梁骨丢失及产后骨量增加的影响。
共有 64 名孕妇在妊娠 16 周时入组，并随机分为在妊娠剩余时间内接受 1000 毫克钙/天或安慰剂治疗。在妊娠 16、26 和 36 周以及产后 4 和 12 个月时测量血清 25-羟维生素 D 和骨转换标志物。通过外周定量计算机断层扫描评估胫骨和桡骨的小梁和皮质骨矿物质密度（BMD）和含量。
基线时平均每日钙摄入量为 733 ± 350 毫克；只有 25%的女性符合 RDA。30 名女性（入组人数的 47%）在产后 12 个月时仍在研究中。在校正基线骨值、血清 25-羟维生素 D 浓度、母乳喂养时间和体重指数后，补钙组在产后 12 个月时桡骨总 BMD（P=0.02）和胫骨皮质 BMD（P=0.03）的增加显著大于安慰剂组。在相同模型中，补钙组的胫骨小梁和总 BMD 也呈现出更高的趋势（P<0.06）。
这些数据表明，在摄入典型美国饮食的女性中，孕期补充钙可能会改善产后骨恢复。需要更大的研究来巩固结论。该试验在 clinicaltrials.gov 上注册为 NCT01145573。
