Grant J D, Bezerra J A, Thompson S H, Lemen R J, Koldovsky O, Udall J N
Department of Pediatrics, University of Arizona College of Medicine, Tucson.
Gastroenterology. 1989 Oct;97(4):895-9. doi: 10.1016/0016-5085(89)91494-7.
Individuals with sufficient intestinal lactase hydrolyze ingested lactose to galactose and glucose and these monosaccharides are absorbed. Lactose is not digested completely when intestinal lactase activity is low and the disaccharide is malabsorbed. Breath hydrogen excretion after lactose ingestion is used commonly to diagnose lactose malabsorption. However, no direct tests are currently used to assess lactose absorption. We tested a new method of assessing lactose absorption in 26 healthy individuals. Each subject ingested 50 g of lactose. Participants were evaluated for lactose malabsorption using a standard 3-h breath hydrogen test. In addition, the urinary excretions of galactose, lactose, and creatinine were quantitated for 3-5 h after lactose ingestion. On the basis of breath hydrogen analysis after lactose ingestion, 12 individuals were lactose malabsorbers (defined as a rise in the breath hydrogen concentration of greater than 20 parts per million above the baseline value). The 14 subjects who did not malabsorb lactose by breath hydrogen testing (defined as a rise in the breath hydrogen concentration of less than or equal to 20 parts per million above the baseline value), had significantly more galactose in their urine 1, 2, and 3 h after lactose ingestion than lactose malabsorbers. The ratio of excreted lactose to excreted galactose was significantly decreased in lactose absorbers compared with lactose malabsorbers (p less than 0.001). Determination of the ratio of urinary galactose to urinary creatinine separated lactose absorbers from lactose malabsorbers completely (p less than 0.001). We conclude from this study that the determination of urinary galactose, urinary lactose/galactose ratio, and urinary galactose/creatinine ratio may be used to assess lactose digestion and absorption in healthy adults.
肠道乳糖酶充足的个体可将摄入的乳糖水解为半乳糖和葡萄糖，这些单糖随后被吸收。当肠道乳糖酶活性较低且二糖吸收不良时，乳糖不能被完全消化。乳糖摄入后呼出氢气的排泄情况常用于诊断乳糖吸收不良。然而，目前尚无直接检测方法用于评估乳糖吸收情况。我们对26名健康个体测试了一种评估乳糖吸收的新方法。每位受试者摄入50克乳糖。使用标准的3小时呼气氢气试验对参与者的乳糖吸收不良情况进行评估。此外，在乳糖摄入后3至5小时对半乳糖、乳糖和肌酐的尿排泄量进行定量分析。根据乳糖摄入后的呼气氢气分析，12名个体为乳糖吸收不良者（定义为呼气氢气浓度比基线值升高超过百万分之20）。通过呼气氢气检测未出现乳糖吸收不良的14名受试者（定义为呼气氢气浓度比基线值升高小于或等于百万分之20），在乳糖摄入后1、2和3小时尿液中的半乳糖含量显著高于乳糖吸收不良者。与乳糖吸收不良者相比，乳糖吸收者中排泄的乳糖与排泄的半乳糖之比显著降低（p小于0.001）。尿半乳糖与尿肌酐之比的测定可将乳糖吸收者与乳糖吸收不良者完全区分开来（p小于0.001）。我们从这项研究得出结论，尿半乳糖、尿乳糖/半乳糖比值和尿半乳糖/肌酐比值的测定可用于评估健康成年人的乳糖消化和吸收情况。
