Ritchie L D, Fung E B, Halloran B P, Turnlund J R, Van Loan M D, Cann C E, King J C
Department of Nutritional Sciences, University of California, Berkeley, USA.
Am J Clin Nutr. 1998 Apr;67(4):693-701. doi: 10.1093/ajcn/67.4.693.
To clarify the role of the intestine, kidney, and bone in maintaining calcium homeostasis during pregnancy and lactation and after the resumption of menses, a longitudinal comparison was undertaken of 14 well-nourished women consuming approximately 1200 mg Ca/d. Measurements were made before conception (prepregnancy), once during each trimester of pregnancy (T1, T2, and T3), early in lactation at 2 mo postpartum (EL), and 5 mo after resumption of menses. Intestinal calcium absorption was determined from the enrichment of the first 24-h urine sample collected after administration of stable calcium isotopes. Bone mineral of the total body and lumbar spine was measured by dual-energy X-ray absorptiometry and quantitative computerized tomography, respectively. Twenty-four-hour urine and fasting serum samples were analyzed for calcium, calcitropic hormones, and biochemical markers of bone turnover. Despite an increase in calcium intake during pregnancy, true percentage absorption of calcium increased from 32.9+/-9.1% at prepregnancy to 49.9+/-10.2% at T2 and 53.8+/-11.3% at T3 (P < 0.001). Urinary calcium increased from 4.32+/-2.20 mmol/d at prepregnancy to 6.21+/-3.72 mmol/d at T3 (P < 0.001), but only minor changes in maternal bone mineral were detected. At EL, dietary calcium and calcium absorption were not significantly different from that at prepregnancy, but urinary calcium decreased to 1.87+/-1.22 mmol/d (P < 0.001) and trabecular bone mineral density of the spine decreased to 147.7+/-21.2 mg/cm3 from 162.9+/-25.0 mg/cm3 at prepregnancy (P < 0.001). Calcium absorption postmenses increased nonsignificantly to 36.0+/-8.1% whereas urinary calcium decreased to 2.72+/-1.52 mmol/d (P < 0.001). We concluded that fetal calcium demand was met by increased maternal intestinal absorption; early breast-milk calcium was provided by maternal renal calcium conservation and loss of spinal trabecular bone, a loss that was recovered postmenses.
为阐明肠道、肾脏和骨骼在妊娠、哺乳期间及月经恢复后维持钙稳态中的作用，对14名每日摄入约1200mg钙的营养良好的女性进行了纵向比较。在受孕前（孕前）、妊娠各期（T1、T2和T3）、产后2个月哺乳早期（EL）以及月经恢复后5个月进行测量。肠道钙吸收通过给予稳定钙同位素后收集的首个24小时尿液样本的富集情况来确定。全身和腰椎的骨矿物质分别通过双能X线吸收法和定量计算机断层扫描进行测量。对24小时尿液和空腹血清样本进行钙、促钙激素和骨转换生化标志物分析。尽管孕期钙摄入量增加，但钙的实际吸收百分比从孕前的32.9±9.1%增加到T2时的49.9±10.2%和T3时的53.8±11.3%（P<0.001）。尿钙从孕前的4.32±2.20mmol/d增加到T3时的6.21±3.72mmol/d（P<0.001），但仅检测到母体骨矿物质有轻微变化。在EL时，膳食钙和钙吸收与孕前无显著差异，但尿钙降至1.87±1.22mmol/d（P<0.001），脊柱小梁骨矿物质密度从孕前的162.9±25.0mg/cm³降至147.7±21.2mg/cm³（P<0.001）。月经后钙吸收无显著增加至36.0±8.1%，而尿钙降至2.72±1.52mmol/d（P<0.001）。我们得出结论，胎儿的钙需求通过母体肠道吸收增加来满足；早期母乳中的钙由母体肾脏保钙和脊柱小梁骨丢失提供，这种丢失在月经后得以恢复。
