O'Brien K O, Abrams S A, Liang L K, Ellis K J, Gagel R F
US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX, U.S.A.
Am J Clin Nutr. 1996 Apr;63(4):579-83. doi: 10.1093/ajcn/63.4.579.
Adequate calcium intake is essential for skeletal integrity, particularly during the period of peak bone mass acquisition from 9 to 17 y of age. Currently, the calcium intake of many adolescent girls is below the recommended dietary allowance. The purpose of this study was to evaluate the ability of girls to respond to acute periods of inadequate dietary calcium intake. Calcium absorption was evaluated in 11 girls aged 11.6 +/- 2.4 y after 10 d on both a low-calcium (7.05 +/- 2.03 mmol/d) and a high-calcium (35.30 +/- 2.28 mmol/d) diet. Fractional calcium absorption was determined by using oral (46Ca) and intravenous (42Ca) stable isotopes of calcium. During a low calcium intake, fractional calcium absorption was significantly greater (0.582 +/- 0.087 compared with 0.260 +/- 0.068, P < 0.0001) and urinary calcium excretion was significantly lower (1.30 +/- 0.83 compared with 3.08 +/- 1.98 mmol/d, P < 0.004) than values obtained during a high calcium intake. Concentrations of 1,25-dihydroxyvitamin D (combination of cholecalciferol and ergocalciferol) were greater during the low calcium intake, although the difference was not significant (108.7 +/- 30.6 compared with 90.0 +/- 25.1 pmol/L, P < 0.1; n = 9). Excretion of N-telopeptide was significantly greater during the low calcium intake (761 +/- 508 compared with 413 +/- 341 nmol bone collagen equivalent (BCM)/mmol creatinine, P < 0.02; n = 9), indicating that bone resorption was increased. These results suggest that during short periods of inadequate calcium intake, girls are able to significantly increase the efficiency of calcium absorption and decrease urinary calcium losses to conserve calcium required for bone mineral acquisition.
充足的钙摄入对骨骼完整性至关重要，尤其是在9至17岁骨量快速增长期。目前，许多青春期女孩的钙摄入量低于推荐膳食摄入量。本研究旨在评估女孩对膳食钙摄入不足急性期的反应能力。对11名年龄为11.6±2.4岁的女孩，在低钙（7.05±2.03 mmol/d）和高钙（35.30±2.28 mmol/d）饮食10天后，评估其钙吸收情况。通过口服（46Ca）和静脉注射（42Ca）钙的稳定同位素来测定钙的吸收分数。低钙摄入期间，钙吸收分数显著更高（分别为0.582±0.087和0.260±0.068，P<0.0001），尿钙排泄显著更低（分别为1.30±0.83和3.08±1.98 mmol/d，P<0.004），均低于高钙摄入时的值。低钙摄入期间1,25-二羟基维生素D（胆钙化醇和麦角钙化醇的组合）浓度更高，尽管差异不显著（分别为108.7±30.6和90.0±25.1 pmol/L，P<0.1；n = 9）。低钙摄入期间N-端肽的排泄显著更高（分别为761±508和413±341 nmol骨胶原当量（BCM）/mmol肌酐，P<0.02；n = 9），表明骨吸收增加。这些结果表明，在钙摄入不足的短期内，女孩能够显著提高钙吸收效率并减少尿钙流失，以保存骨矿物质获取所需的钙。
