Atkinson Stephanie A, Koletzko Berthold
Department of Pediatrics, Faculty of Health Sciences, 3G57, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.
Food Nutr Bull. 2007 Mar;28(1 Suppl International):S61-76. doi: 10.1177/15648265070281S107.
The derivation of reference values in 11 current dietary reference standards is often based on methods of extrapolation or interpolation, but these are not consistent across reports. Such methods are frequently employed to derive nutrient intake values (NIVs) for infants and children owing to the paucity of relevant research data available. The most common method is to extrapolate values for children down from those of adults, employing a weight or metabolic factor and adjusting for growth. In some instances, values for young children are extrapolated up from infants, values for adults are extrapolated up from children, or values for older adults are extrapolated up from young adults. Extrapolation is employed to estimate not only nutrient requirement or adequate intake but also the upper tolerable levels of intake. Extrapolation methods may also form the basis of estimates of tissue deposition of nutrients during growth in children and for the maternal/fetal dyad in pregnancy with adjustments for metabolic efficiency. Likewise, recommended intakes during lactation are extrapolated from known secretion of the nutrient in milk with adjustments for bioavailability. For future dietary standards, a first priority is to obtain relevant scientific data using current methodology, such as stable isotope tracers, body composition analysis, and appropriate biomarkers, from which NIVs for each age group can be derived. Extrapolation to derive an NIV is only acceptable in the sheer absence of sound scientific data and must be modeled with a consistent approach. For the purpose of harmonization of dietary standards, we recommend the following approaches that should be clearly described in reports: standardization of age groups on a biological basis (growth and pubertal stages) with consideration of relevant developmental milestones throughout childhood; application of internationally accepted standards for growth, body size, body composition, fetal and maternal nutrient accretion in pregnancy, and milk composition; and inclusion of appropriate adjustments (metabolic efficiency, weight change, or physical activity).
11种现行膳食参考标准中参考值的推导通常基于外推法或内插法，但这些方法在不同报告中并不一致。由于缺乏可用的相关研究数据，此类方法经常被用于推导婴幼儿和儿童的营养素摄入量值（NIVs）。最常见的方法是根据成人的数值向下外推儿童的数值，采用体重或代谢因子并根据生长情况进行调整。在某些情况下，幼儿的数值是从婴儿数值向上外推得到的，成人的数值是从儿童数值向上外推得到的，或者老年人的数值是从年轻人的数值向上外推得到的。外推法不仅用于估计营养素需求量或适宜摄入量，还用于估计摄入量的可耐受上限。外推法也可能构成儿童生长期间以及孕期母婴二元组营养素组织沉积估计的基础，并对代谢效率进行调整。同样，哺乳期的推荐摄入量是根据乳汁中营养素的已知分泌量并对生物利用率进行调整后外推得出的。对于未来的膳食标准，首要任务是使用当前方法，如稳定同位素示踪剂、身体成分分析和适当的生物标志物，获取相关科学数据，从中可以得出各年龄组的NIVs。只有在完全缺乏可靠科学数据的情况下，外推得出NIV才是可接受的，并且必须采用一致的方法进行建模。为了统一膳食标准，我们建议在报告中应清晰描述以下方法：在生物学基础上（生长和青春期阶段）对年龄组进行标准化，并考虑整个儿童期的相关发育里程碑；应用国际公认的生长、身体大小、身体成分、孕期胎儿和母体营养素积累以及乳汁成分标准；并纳入适当的调整（代谢效率、体重变化或身体活动）。
