Roberts S B, Coward W A, Ewing G, Savage J, Cole T J, Lucas A
Department of Applied Biological Sciences, Massachusetts Institute of Technology, Cambridge 02139.
Am J Physiol. 1988 Apr;254(4 Pt 2):R622-7. doi: 10.1152/ajpregu.1988.254.4.R622.
Variations in background 2H and 18O abundances in body water influence the accuracy and precision of the 2H218O method for determination of energy expenditure. To investigate the effect of weaning during infancy on background 2H and 18O abundances, urine samples from 44 breast- or formula-fed infants aged 5-16 wk were analyzed. 2H and 18O abundances were significantly higher (P less than 0.001) in breast- than in formula-fed infants. The relationship between 2H and 18O abundances was linear and independent of diet [slope, 4.16 +/- 0.43 (SE)]. By use of this information, the effect of weaning on the accuracy of the 2H218O method was evaluated, taking into account the effect of 2H-18O abundances in the isotope loading dose. In infants weaned completely from breast milk to formula during the measurement, energy expenditure can be overestimated by 18.0%, even if 2H-18O abundances in the isotope dose equal the ratio of naturally occurring background changes. However, this error can be reduced to less than 3.0% by manipulating the study duration and isotope dose. During gradual weaning, the overestimation of energy expenditure is only 0.3-2.0%.
体内水分中背景氘（2H）和氧-18（18O）丰度的变化会影响用2H218O法测定能量消耗的准确性和精密度。为了研究婴儿期断奶对背景氘和氧-18丰度的影响，分析了44名年龄在5 - 16周的母乳喂养或配方奶喂养婴儿的尿液样本。母乳喂养婴儿的氘和氧-18丰度显著高于配方奶喂养婴儿（P小于0.001）。氘和氧-18丰度之间的关系呈线性，且与饮食无关[斜率，4.16±0.43（标准误）]。利用这些信息，在考虑同位素加载剂量中氘-氧-18丰度影响的情况下，评估了断奶对2H218O法准确性的影响。在测量期间从母乳完全断奶至配方奶喂养的婴儿中，即使同位素剂量中的氘-氧-18丰度等于自然发生的背景变化比例，能量消耗仍可能被高估18.0%。然而，通过控制研究持续时间和同位素剂量，这一误差可降低至3.0%以下。在逐渐断奶期间，能量消耗的高估仅为0.3 - 2.0%。
