Colley R C, Byrne N M, Hills A P
School of Human Movement Studies, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
Eur J Clin Nutr. 2007 Nov;61(11):1250-5. doi: 10.1038/sj.ejcn.1602653. Epub 2007 Feb 7.
To investigate the variability in isotopic equilibrium time under field conditions, and the impact of this variability on estimates of total body water (TBW) and body composition.
Following collection of a fasting baseline urine sample, 10 women and 10 men were dosed with deuterium oxide (0.05 g/kg body weight). Urine samples were collected every hour for 8 h. The samples were analysed using isotope ratio mass spectrometry. Time to equilibration was determined using three commonly employed data analysis approaches.
Isotopic equilibrium was reached by 50, 80 and 100% of participants at 4, 6 and 8 h, respectively. The mean group equilibration determined using the three different plateau determination methods were 4.8+/-1.5, 3.8+/-0.8 and 4.9+/-1.4 h. Isotopic enrichment, TBW, and percent body fat estimates differed between early (3-5 h), but not later sampling times (5-8 h).
Although the three different plateau determination approaches resulted in differences in equilibration time, all suggest that sampling at 6 h or later will decrease the likelihood of error in body composition estimates resultant from incomplete isotopic equilibration in a small proportion of individuals.
研究野外条件下同位素平衡时间的变异性，以及这种变异性对总体水（TBW）和身体成分估计值的影响。
在采集空腹基线尿液样本后，给10名女性和10名男性服用氧化氘（0.05 g/kg体重）。每小时采集尿液样本，共采集8小时。使用同位素比率质谱法对样本进行分析。使用三种常用的数据分析方法确定达到平衡的时间。
分别有50%、80%和100%的参与者在4小时、6小时和8小时达到同位素平衡。使用三种不同的平稳期确定方法确定的平均组平衡时间分别为4.8±1.5小时、3.8±0.8小时和4.9±1.4小时。早期（3 - 5小时）的同位素富集、TBW和体脂百分比估计值存在差异，但后期采样时间（5 - 8小时）则无差异。
尽管三种不同的平稳期确定方法导致平衡时间存在差异，但所有方法均表明，在6小时或更晚进行采样将降低因一小部分个体同位素未完全平衡而导致身体成分估计误差的可能性。
