PhD, The University of Georgia, 279 Dawson Hall, Athens, GA 30602.
J Clin Endocrinol Metab. 2013 Dec;98(12):4816-25. doi: 10.1210/jc.2013-2728. Epub 2013 Oct 3.
Changes in serum vitamin D metabolites and calcium absorption with varying doses of oral vitamin D₃ in healthy children are unknown.
Our objective was to examine the dose-response effects of supplemental vitamin D₃ on serum vitamin D metabolites and calcium absorption in children living at two U.S. latitudes.
Black and white children (n = 323) participated in a multisite (U.S. latitudes 34° N and 40° N), triple-masked trial. Children were randomized to receive oral vitamin D₃ (0, 400, 1000, 2000, and 4000 IU/d) and were sampled over 12 weeks in winter. Serum 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)₂D) were measured using RIA and intact PTH (iPTH) by immunoradiometric assay. Fractional calcium absorption was determined from an oral stable isotope ⁴⁴Ca (5 mg) in a 150-mg calcium meal. Nonlinear and linear regression models were fit for vitamin D metabolites, iPTH, and calcium absorption.
The mean baseline 25(OH)D value for the entire sample was 70.0 nmol/L. Increases in 25(OH)D depended on dose with 12-week changes ranging from -10 nmol/L for placebo to 76 nmol/L for 4000 IU. Larger 25(OH)D gains were observed for whites vs blacks at the highest dose (P < .01). Gains for 1,25(OH)₂D were not significant (P = .07), and decreases in iPTH were not dose-dependent. There was no dose effect of vitamin D on fractional calcium absorption when adjusted for pill compliance, race, sex, or baseline 25(OH)D.
Large increases in serum 25(OH)D with vitamin D₃ supplementation did not increase calcium absorption in healthy children living at 2 different latitudes. Supplementation with 400 IU/d was sufficient to maintain wintertime 25(OH)D concentrations in healthy black, but not white, children.
目前尚不清楚不同剂量口服维生素 D₃对健康儿童血清维生素 D 代谢物和钙吸收的影响。
本研究旨在检测美国两个不同纬度地区补充维生素 D₃对儿童血清维生素 D 代谢物和钙吸收的剂量反应。
323 名黑人和白人儿童参与了一项多中心（美国纬度 34°N 和 40°N）、三盲试验。儿童随机接受口服维生素 D₃（0、400、1000、2000 和 4000IU/d），并在冬季 12 周内进行采样。血清 25-羟维生素 D（25(OH)D）和 1,25-二羟维生素 D（1,25(OH)₂D）采用放射免疫分析法检测，完整甲状旁腺激素（iPTH）采用免疫放射分析法检测。通过口服稳定同位素 ⁴⁴Ca（5mg）在 150mg 钙餐中测定钙的分数吸收。对维生素 D 代谢物、iPTH 和钙吸收进行非线性和线性回归模型拟合。
整个样本的平均基线 25(OH)D 值为 70.0nmol/L。25(OH)D 的增加取决于剂量，12 周的变化范围从安慰剂组的-10nmol/L到 4000IU 组的 76nmol/L。在最高剂量时，白人的 25(OH)D 增加幅度大于黑人（P<.01）。1,25(OH)₂D 的增加不显著（P=0.07），iPTH 的下降与剂量无关。当根据药丸依从性、种族、性别或基线 25(OH)D 调整时，维生素 D 对钙分数吸收没有剂量效应。
补充维生素 D₃可使血清 25(OH)D 大幅增加，但在生活于两个不同纬度的健康儿童中，并未增加钙的吸收。每天补充 400IU 维生素 D 可维持健康的黑人和白人儿童冬季 25(OH)D 浓度。
