Dietary potential renal acid load and renal net acid excretion in healthy, free-living children and adolescents
健康、自由生活的儿童和青少年 的膳食潜在肾酸负荷和肾净酸排泄

Background: There is increasing evidence that acid-base status has a significant effect on high-intensity physical performance, urolithiasis, and calcium metabolism. Experimental studies in adults showed that renal net acid excretion (NAE) can be reliably estimated from the composition of diets.
背景：越来越多的证据表明，酸碱状态对高强度身体机能、尿石症和钙代谢有显着影响。成人的实验研究表明，肾净酸排泄（NAE）可以从饮食成分中可靠地估计出来。

Objective: We investigated whether a reasonable estimation of NAE is also possible from the dietary records of free-living children and adolescents.
目的：我们调查了从自由生活的儿童和青少年的饮食记录中是否也可以合理估计NAE。

Design: Healthy children (aged 8 y; ) and adolescents (aged 16-18 y; ) each collected a 24-h urine sample and completed a weighed diet record on the same day. Urinary NAE was analyzed and estimated . Potential renal acid load (PRAL), the diet-based component of , corrects for intestinal absorption of ingested minerals and sulfur-containing protein. A urinary excretion rate of organic acids (OAs) proportional to body surface area was assumed for the complete estimate .
设计：健康儿童（8岁; ）和青少年（16-18岁; ）收集了24小时的尿液样本，并在同一天完成了称重饮食记录。分析 和估计 尿NAE。潜在肾酸负荷 （PRAL） 是基于饮食的 成分，可校正肠道对摄入的矿物质和含硫蛋白质的吸收。假设有机酸 （OA） 的尿排泄率与体表面积成正比，以进行完整估计 。

Results: Significant correlations between NAE and were seen in the children and the adolescents . A simplified estimate based on only 4 components of dietary PRAL (protein, phosphorus, potassium, and magnesium) yielded almost identical associations. Mean simplified NAE and in the children and the adolescents, respectively) agreed reasonably with NAE and , respectively).
结果：NAE 与 儿童 和青少年之间有显著 相关性 。仅基于膳食 PRAL 的 4 种成分（蛋白质、磷、钾和镁）的简化估计产生了几乎相同的关联。均值简化 NAE 和 分别在儿童和青少年中）分别与 NAE 和 合理一致）。

Conclusions: Predicting NAE from dietary intakes, food tables, and anthropometric data is also applicable during growth and yields appropriate estimates even when self-selected diets are consumed. The PRAL estimate based on only 4 nutrients may allow relatively simple assessment of the acidity of foods and diets. Am J Clin Nutr 2003;77:1255-60.
结论：根据饮食摄入量、食物表和人体测量数据预测 NAE 也适用于生长过程，即使在食用自选饮食时也能产生适当的估计值。仅基于 4 种营养素的 PRAL 估计可能允许相对简单地评估食物和饮食的酸度。美国临床营养杂志 2003;77：1255-60。

KEY WORDS Biomarkers, children, adolescents, dietary record, food table, mineral intake, nutrient bioavailability, potential renal acid load, protein intake, renal net acid excretion, 24-h urine collection
关键词 生物标志物， 儿童， 青少年， 饮食记录， 食物表， 矿物质摄入量， 营养素生物利用度， 潜在肾酸负荷， 蛋白质摄入， 肾净酸排泄， 24小时尿液收集

Acid-base status is becoming increasingly important in nutritional medicine and related fields. For example, in sports medicine, alkalization has been shown to increase the capacity for high-intensity exercise . In clinical nutrition, the use of infant and preterm formulas that are not appropriately composed and that contain excessive amounts of acid equivalents was shown to cause catabolic effects including growth retardation of the infants (3-6). Similar negative effects can occur if inadequately composed synthetic amino acid mixtures and protein hydrolyzates are fed (7). Several nephrologic diseases, such as urolithiasis and renal insufficiency, require both control and manipulation of acidbase status (8-12).
酸碱状态在营养医学和相关领域变得越来越重要。例如，在运动医学中，碱化已被证明可以增加高强度运动 的能力。在临床营养学中，使用成分不适当且含有过量酸当量的婴儿和早产儿配方奶粉被证明会导致分解代谢作用，包括婴儿生长迟缓（3-6）。如果饲喂合成氨基酸混合物和蛋白质水解物不充分，也会发生类似的负面影响 （7）。一些肾病，如尿石症和肾功能不全，需要控制和操纵酸碱状态 （8-12）。

Furthermore, acid-base status appears to be important in osteology. In vitro studies have shown a measurable calcium efflux from bone under acidosis-like metabolic conditions (13). Accordingly, in epidemiologic surveys, strong positive associations have been observed between rates of hip fracture in women and indexes of dietary animal protein intake (a major source of endogenous acid production) . In contrast, the ingestion of doses of alkalizing potassium bicarbonate sufficient to neutralize endogenous acid was shown to improve calcium balance, reduce bone resorption, and increase the rate of bone formation in postmenopausal women (16).
此外，酸碱状态在骨学中似乎很重要。体外研究表明，在酸中毒样代谢条件下，骨中可测量钙外流 （13）。因此，在流行病学调查中，观察到女性髋部骨折发生率与膳食动物蛋白摄入量指数（内源性酸产生的主要来源） 之间有很强的正相关关系。相比之下，摄入足以中和内源性酸的碱化碳酸氢钾剂量可改善绝经后妇女的钙平衡，减少骨吸收并增加骨形成率（16）。

Today, there is a general consensus that diet can markedly affect acid-base status and that a person's acid load can be specifically manipulated by dietary means (9, 17-21). An established method of estimating acid loads of foods or diets is by calculating the potential renal acid load (PRAL) (9, 22, 23). PRAL provides an estimate of the production of endogenous acid that exceeds the level of alkali produced for given amounts of foods ingested daily. The concept of PRAL calculation is physiologically based and takes into account different intestinal absorption rates of individual minerals and of sulfurcontaining protein, as well as the amount of sulfate produced from metabolized proteins. This method of calculation was experimentally validated in healthy adults, and it showed that, under controlled conditions, acid loads and renal net acid excretion (NAE) can be reliably estimated from diet composition (18). The purpose of the present study was to investigate whether a reasonable estimation of acid loads (quantified as NAE in 24-h urine samples) is also possible from dietary records of free-living children and adolescents.
今天，有一个普遍的共识，饮食可以显着影响酸碱状态，并且一个人的酸负荷可以通过饮食方式专门操纵（9,17-21）。估计食物或饮食的酸负荷的既定方法是通过计算潜在的肾酸负荷（PRAL）（9,22,23）。PRAL提供了内源性酸产量的估计值，该内源性酸的产量超过了每天摄入的给定量食物所产生的碱水平。PRAL计算的概念是基于生理学的，它考虑了单个矿物质和含硫蛋白质的不同肠道吸收率，以及代谢蛋白质产生的硫酸盐量。这种计算方法在健康成人中得到了实验验证，它表明，在受控条件下，可以从饮食成分中可靠地估计酸负荷和肾净酸排泄 （NAE） （18）。本研究的目的是调查是否也可以从自由生活的儿童和青少年的饮食记录中合理估计酸负荷（量化为 24 小时尿液样本中的 NAE）。

The study was performed in a cross-sectional sample of 165 healthy children aged 8 y and 73 adolescents aged 16-18 y. The subjects were all participants in the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study, an ongoing observational study of the interrelations among nutrition, growth, and metabolic and endocrine changes during childhood and adolescence. The study was approved by the institutional review board of the Research Institute of Child Nutrition Dortmund, and informed parental consent and each child's oral assent were obtained before entry into the study. Besides age, a further inclusion criterion was the completion of a 3-d weighed diet record and the collection of one 24-h urine sample during the 3-d period. Only the nutrient intakes recorded on the day of urine collection were used for the estimation of NAE and PRAL.
该研究是在 165 名 8 岁健康儿童和 73 名 16-18 岁青少年的横断面样本中进行的。受试者都是多特蒙德营养和人体测量纵向设计 （DONALD） 研究的参与者，这是一项正在进行的观察性研究，研究儿童和青春期营养、生长以及代谢和内分泌变化之间的相互关系。该研究得到了多特蒙德儿童营养研究所机构审查委员会的批准，并在进入研究之前获得了父母的知情同意和每个孩子的口头同意。除年龄外，进一步的纳入标准是完成 3 天称重饮食记录并在 3 天期间收集一份 24 小时尿液样本。仅使用尿液收集当天记录的营养摄入量来估计 NAE 和 PRAL。

To exclude major errors in the 24-h urine collection, those samples that were reported to contain incomplete micturitions or that showed a daily creatinine excretion rate body , or both (24), were not considered. Details of the urine collection procedure were reported recently (24). Subjects were asked to follow their usual diets on the day of urine collection. Parents of the children (or the adolescents themselves) weighed and recorded all foods and fluids consumed and all leftovers with the use of electronic food scales (Wedo Digi 2000; Werner Dorsch GmbH, Rödermark, Germany). Product information from wrappers, cartons, and other containers of new or special food items not included in the food tables (see below) were kept and evaluated with the dietary records by our dietitians (25).
为了排除 24 小时尿液收集中的重大错误，不考虑那些报告包含不完全排尿或显示每日肌酐排泄率 的 样本，或两者兼而有之 （24）。最近报道了尿液收集程序的细节（24）。受试者被要求在收集尿液的当天遵循他们通常的饮食习惯。儿童的父母（或青少年自己）使用电子食物秤称重并记录所有食用的食物和液体以及所有剩菜（Wedo Digi 2000;Werner Dorsch GmbH， Rödermark， 德国）。来自包装纸、纸箱和其他容器中未包含在食物表（见下文）中的新食品或特殊食品的产品信息由我们的营养师保存并与饮食记录一起评估 （25）。

To validate dietary recording, the ratio of reported energy intake to predicted basal metabolic rate was calculated according to the method of Goldberg et al (26) with prior calculation of basal metabolic rate according to the method of Schofield (27). Records with individual ratios of energy intake to basal metabolic rate of were excluded from this study. The nutrient and energy contents of foods were taken from European standard nutrient tables , preferentially from those of Souci et al (30). Around the time of completion of the dietary record and urine collection, all children were examined by a pediatrician, and anthropometric measurements were obtained. Body weight was measured to the nearest and height was measured to the nearest with the use of an electronic scale (Seca 753 E; Seca Weighing and Measuring Systems, Hamburg, Germany) and a digital, telescopic, wall-mounted stadiometer (Harpenden; Holtain Ltd, Crymych, United Kingdom), respectively.
为了验证饮食记录，根据 Goldberg 等人 （26） 的方法计算报告的能量摄入与预测的基础代谢率的比率，并根据 Schofield （27） 的方法计算基础代谢率。本研究排除了能量摄入与基础代谢率的个体比率的记录 。食物的营养素和能量含量取自欧洲标准营养表，优先取自Souci等人（30）的营养表 。在完成饮食记录和尿液收集时，所有儿童都由儿科医生检查，并进行了人体测量。 使用电子秤（Seca 753 E;Seca Weighing and Measuring Systems，德国汉堡）和数字、伸缩式、壁挂式测距仪（Harpenden;Holtain Ltd， Crymych， United Kingdom），分别。

Acid-base status was determined in the freshly thawed 24-h samples. Urine , titratable acid (TA), ammonium , and bicarbonate were measured according to the method of Lüthy et al (31). Quantification of organic acids (OAs) was carried out according to the method of van Slyke and Palmer (32). NAE was calculated from the analytic data in the conventional manner as the sum of TA plus minus . Aliquots of all 24-h urine samples were stored for subsequent analysis. The cations potassium, magnesium, and calcium were measured by flame atomic absorption spectrometry (Perkin Elmer 1100 Spectrometer; Perkin Elmer, Überlingen, Germany); the detection limit is , and the intraassay and interassay precision is . Sulfate and phosphate were measured with a Dionex
在新鲜解冻的 24 小时样品中测定酸碱状态。尿 液、可滴定酸（TA）、铵 和碳酸 氢盐按照Lüthy等人的方法测定（31）。根据van Slyke和Palmer（32）的方法进行有机酸（OAs）的定量。根据分析数据，以常规方式计算 NAE 为 TA 加 减去 的总和 。储存 所有 24 小时尿液样本的等分试样以供后续分析。阳离子钾、镁和钙采用火焰原子吸收光谱法（Perkin Elmer 1100 Spectrometer;Perkin Elmer，Überlingen，德国）;检测限为 ，测定内和测间精密度为 。硫酸盐和磷酸盐用 Dionex 测量
Ion chromatograph with an ion Pac AS4A column (Dionex GmbH, Idstein, Germany). Urinary creatinine was measured with the use of the kinetic Jaffé test (33) on a creatinine analyzer (Beckman-2; Beckman Instruments Inc, Fullerton, CA) according to the manufacturer's instructions.
离子色谱仪，离子Pac AS4A色谱柱（Dionex GmbH，Idstein，德国）。使用肌酐分析仪（Beckman-2;Beckman Instruments Inc， Fullerton， CA）根据制造商的说明。

Because the sum of cations excreted in urine equals the sum of anions, urinary NAE ( cationic TA anionic ) is also equal to the difference between the sum of the major urinary nonbicarbonate anions (chloride, phosphate, sulfate, and OAs) minus the sum of the non-TA and non- cations (sodium, potassium, magnesium, and calcium). The amounts of these nonbicarbonate anions and mineral cations in urine, except OAs, are primarily influenced by nutritional intake. OAs are mainly determined by body surface area and can thus be estimated from anthropometric measurements body surface area . The diet-based estimate of the urinary difference of nonbicarbonate anions (without OAs) and mineral cations is PRAL. To calculate PRAL, average intestinal net absorption rates of relevant nutrients (including protein to estimate sulfate) must be considered together with the grade of dissociation of phosphate at and the ionic valence of magnesium and calcium . On the basis of these PRAL-determining factors (and after the respective atomic weights are taken into account), nutrient-specific conversion factors are obtained that allow the calculation of PRAL directly from dietary intakes (9):
因为尿液中排泄的阳离子总和等于阴离子的总和，所以尿NAE（ 阳离子 TA阴离子 ）也等于主要尿非碳酸氢盐阴离子（氯化物、磷酸盐、硫酸盐和OAs）的总和减去非TA和非 阳离子（钠、钾、镁和钙）的总和之间的差值。尿液中这些非碳酸氢盐阴离子和矿物质阳离子的含量（OAs除外）主要受营养摄入的影响。OA主要由体表面积决定，因此可以通过人体测量 测量体表面积 来估计。基于饮食的非碳酸氢盐阴离子（不含 OA）和矿物阳离子尿液差异的估计值为 PRAL。为了计算PRAL，必须考虑相关营养素（包括估计硫酸盐的蛋白质）的平均肠道净吸收率以及磷酸盐的 解离等级以及镁和钙的离子价 。根据这些PRAL决定因素（在考虑各自的原子量之后），获得营养素特异性转换因子，允许直接从膳食摄入量计算PRAL（9）：

For the estimation of total urinary NAE, OA was considered in addition to PRAL PRAL .
对于总尿NAE的估计，除了PRAL PRAL 之外，还考虑了OA。

In contrast to earlier studies that evaluated a limited number of foods and beverages , sodium and chloride were omitted from the present calculation of PRAL because, for some of the foods recorded, either the chloride data are missing from the food tables used, or, in the case of processed (salted) foods, they deviate unrealistically by more than from the respective sodium values (9). This omission implies a certain insensitivity of our calculation to large differences in the intakes of these elements. As calculated from differences in urinary chloride and sodium excretion after the controlled ingestion of different diets, the resulting estimation error for PRAL can be as much as (18). However, in 24-h urine samples from randomly selected children and adolescents from the DONALD Study, the mean urinary ratio of sodium to chloride was found to be 1.02 (35).
与早期评估有限数量的食品和饮料的研究相比 ，钠和氯化物在目前的PRAL计算中被省略了，因为对于一些记录的食物，所使用的食物表中缺少氯化物数据，或者，在加工（咸制）食品的情况下，它们不切实际地偏离了 从各自的钠值 （9）。这种遗漏意味着我们的计算对这些元素摄入量的巨大差异不敏感。根据控制摄入不同饮食后尿氯化物和钠排泄的差异计算，PRAL的估计误差可能高达 （18）。然而，在DONALD研究中随机选择的儿童和青少年的24小时尿液样本中，发现钠与氯化物的平均尿液比值为1.02（35）。

Data are presented as means SDs. Pearson's correlation coefficients, a paired test, and two-way analysis of variance (factors: age group and sex) were performed. In clinical comparison of a new measurement technique with an established one, the BlandAltman limits of agreement (36) are usually calculated, but that was not done in the present study because measurement and estimation techniques were compared. Instead, Pitman's test (37) was used to determine statistically whether NAE may allow a better assessment of acid-base status (criterion
数据以均值 SD 的形式呈现。 进行了 Pearson 相关系数、配对 检验和方差（因素：年龄组和性别）的双向分析。在将新的测量技术与已建立的测量技术进行临床比较时，通常会计算 BlandAltman 一致性限 （36），但本研究中没有这样做，因为比较了测量 和估计 技术。取而代之的是，Pitman检验（37）用于统计学上确定NAE 是否允许更好地评估酸碱状态（标准

TABLE 1 表1

Baseline characteristics (anthropometric, nutritional, and urinary) of the study population according to age and sex
根据年龄和性别 划分的研究人群的基线特征（人体测量、营养和泌尿系统）

variable: analyzed 24-h NAE) than does a recently proposed alternative, diet estimate (20). Residuals of the regressions of the criterion variable with both estimation models were calculated (residuals and ; the sum and the difference were calculated, and then was correlated with . If this correlation differed significantly from zero, the residual with the smaller SD was the model with better fit. Significance was set at , and all tests were two-tailed. Analyses were performed with the use of SAS for WINDOWS software (38).
变量：分析了 24 小时 NAE）而不是最近提出的替代方案，饮食估计 （20）。计算两种估计模型下准则变量回归的残差（残差 和 ;计算和 差，然后 与 相关联。如果这种相关性与零有显著差异，则SD越小的残差越好，则模型拟合越好。显著性被设定为 ，所有测试都是双尾的。使用SAS for WINDOWS软件进行分析（38）。

Anthropometric baseline characteristics, dietary intakes of energy and total protein, and 24-h urinary creatinine output of the subjects are shown in Table 1. In both age groups, correlations between estimated and analyzed urinary electrolytes were highly significant for sulfate, phosphate, and potassium and
受试者的人体测量基线特征、能量和总蛋白质的膳食摄入量以及 24 小时尿肌酐输出如表 1 所示。在两个年龄组中，估计和分析的尿电解质之间的相关性对于硫酸盐、磷酸盐和钾 和

OAs and significant for magnesium (Table 2). Correlations for calcium were significant only in the 8-y-old children. Comparable clear associations were seen for both forms of (with or without calcium inclusion) with (Table 2). Correlation coefficients remained in the same range after simplified NAE and were corrected for energy intake. Correspondingly, the simplified PRAL, which is also based on intakes of only 4 nutrients (without calcium), correlated highly significantly with the sum of the corresponding analyzed urine variables (Table 2 ). Significant differences between estimated and analyzed mean values of all electrolytes were seen in the 8 -y-old children. In the adolescent group, most of the differences were not significant. Differences in relative values (means of estimated values as a percentage of analyzed means) were largest for calcium. Absolute differences were in the range of 0.6 (for magnesium in 8 -y-old boys) to (for potassium in male adolescents).
OAs 对镁有意义 （表2）。钙的相关性仅在 8 岁儿童中显著 。两种形式 （有或没有钙包涵体）与 （表2）具有可比的明显关联。简化NAE后，相关系数保持在同一范围内，并 针对能量摄入进行了校正。相应地，简化的PRAL也仅基于4种营养素（不含钙）的摄入量，与相应分析的尿液变量的总和高度显着 相关（表2）。在8岁儿童中，所有电解质的估计值和分析平均值之间存在显着 差异。在青少年组中，大多数差异并不显着。钙的相对值（估计值的平均值占分析平均值的百分比）的差异最大。绝对差异在0.6（8岁男孩的镁）到 （男性青少年的钾）的范围内。

Comparison and correlation of potential renal acid load (PRAL), estimated net acid excretion ( ), and estimates of single urinary determinants of NAE (sulfate, phosphate, potassium, magnesium, calcium, and organic acids) with the respective data analyzed in 24-h urine samples
潜在肾酸负荷 （PRAL）、估计净酸排泄 （ ） 和 NAE 的单个尿决定因素（硫酸盐、磷酸盐、钾、镁、钙和有机酸）的估计值与 24 小时尿液样本 中分析的相应数据的比较和相关性

, analyzed NAE.
，分析了NAE。

Significantly different from estimated, (paired test).
与估计值显著不同（ 配对 检验）。

.

.

.

With calcium.  含钙。

Without calcium. Estimated sulfate + phosphate - potassium - magnesium + organic acids.
不含钙。估计 硫酸盐+磷酸盐-钾-镁+有机酸。

PRAL estimated sulfate + phosphate - potassium - magnesium. PRAL compared with the sum of corresponding urinary analytes (analyzed PRAL).
PRAL 估计硫酸盐+磷酸盐-钾-镁。PRAL与相应尿液分析物的总和（分析PRAL）进行比较。

FIGURE 1. Twenty-four-hour urinary net acid excretion (NAE) in children and adolescents plotted against A) simplified estimated NAE ( NAE ) and ) the ratio of dietary protein to potassium ( 8 -y-old group: boys, 83 girls; -y-old group: males, 29 females).
图 1.儿童和青少年的 24 小时尿净酸排泄 （NAE） 与 A） 简化估计 NAE （NAE ） 和 ）膳食蛋白质与钾的比率作图（8 岁组： 男孩，83 女孩; -y-old 组： 男性，29 名女性）。

The that included calcium underestimated in all groups, significantly so in the 8 -y-old children and in the adolescent girls. In comparing simplified NAE and PRAL (both without calcium) with the corresponding analyzed values, overestimations were seen (except for simplified in 8 -y-old boys), but most were not significant (Table 2). Correspondingly, when the sexes were combined, means of simplified coincided with in 8 -y-old children ( versus and adolescents ( versus . The sex differences that were present for simplified and were no longer significant after these variables had been corrected for individual energy intake. For respective mean values, see Table 2; values from two-way analysis of variance for the factor sex were for simplified for , for energy-corrected simplified , and for energy-corrected . Both simplified and the ratio of protein to potassium are shown in Figure 1 to be significantly correlated with . However, the correlation coefficient was lower for the relation with protein:potassium, which is an alternative estimate of the alkalizing or acidifying potential of diets (20). Pitman's test yielded significantly smaller SDs of the residuals for the regression of on when compared with protein:potassium.
所有组的钙含量都被低估 了，在8岁儿童和青春期女孩中尤其如此。在将简化的NAE和PRAL（均不含钙）与相应的分析值进行比较时，可以看到高估（除了8岁男孩的简化 ），但大多数并不显着（表2）。相应地，当两性合并时，简化的均值 与 8 岁儿童 （ 与 青少年 （ 与 .简化后存在的性别差异 在针对个体能量摄入校正这些变量后不再显着。有关各自的平均值，见表2; 因子性别的双向方差分析的值为 简化 的、 能量校正的简化 和 能量校正 的。图 1 显示，简化 和蛋白质与钾的比率都与 显著 相关。然而，与蛋白质：钾的关系系数较低，蛋白质：钾是饮食碱化或酸化潜力的另一种估计值（20）。与蛋白质：钾相比，Pitman 的测试产生了 on 回归残差的 SD 明显更小。

The results of this cross-sectional study indicate that an appropriate prediction of average urinary NAE is possible for healthy children and adolescents with the use of a simplified model for calculating PRAL. The PRAL estimate, which is based on food consumption according to a 24-h weighed diet record and the corresponding intakes of only 4 nutrients (as specified in standard food composition tables), was highly significantly correlated with in 24-h urine samples.
这项横断面研究的结果表明，使用简化模型计算 PRAL 可以适当预测健康儿童和青少年的平均尿 NAE。PRAL估计值基于24小时称重饮食记录的食物消耗量和仅4种营养素的相应摄入量（如标准食物成分表中规定的那样），与 24小时尿液样本高度显着相关。

Similar associations with were seen for , ie, for the PRAL plus an anthropometrically based estimate of the daily OA production rate, which usually varies moderately among different diets (18). The inclusion of estimated OA allowed a fairly good prediction of the total amount of actual NAE in children and adolescents. This absolute NAE prediction did not improve when dietary calcium was considered along with the intakes of protein, phosphate, potassium, and magnesium. As is widely recognized and also observed in the present study, the association between dietary estimated and renally excreted calcium is very weak. Data on urinary anion and cation balance regularly indicate that renal calcium output contributes less to overall urinary NAE than does any other mineral cation or nonbicarbonate anion . In a previous diet experiment, during which calcium intake was more strictly controlled, an overestimation of urinary calcium output by -fold was observed (18). This was similar to the present misestimations. Finally, renal calcium excretion is influenced by acid-base status itself as well as by sodium chloride ingestion. For all these reasons, it appears appropriate to use the simplified (and PRAL calculation formula) that is based on only 4 dietary components and that no longer takes dietary calcium into account.
与以下因素有类似的关联 ，即PRAL加上基于人体测量学的每日OA产生率估计值，该估计值通常在不同饮食中略有不同（18）。纳入估计的 OA 可以很好地预测儿童和青少年的实际 NAE 总量。当将膳食钙与蛋白质、磷酸盐、钾和镁的摄入量一起考虑时，这种绝对 NAE 预测并未改善。正如本研究广泛认可和观察到的那样，膳食估计和肾脏排泄钙之间的关联非常弱。关于尿阴离子和阳离子平衡的数据经常表明，肾钙输出对整体尿 NAE 的贡献小于任何其他矿物质阳离子或非碳酸氢盐阴离子 。在先前的饮食实验中，钙摄入量受到更严格的控制，观察到尿钙输出量被高估了 - 倍 （18）。这与目前的错误估计相似。最后，肾钙排泄受酸碱状态本身以及氯化钠摄入的影响。由于所有这些原因，使用仅基于 4 种膳食成分且不再考虑膳食钙的简化 （和 PRAL 计算公式）似乎是合适的。

Overall, NAE that included calcium underestimated NAE in all groups (mostly significant), whereas simplified and PRAL (both without calcium) moderately (mostly nonsignificantly) overestimated and analyzed PRAL, respectively. There was one exception to this uniform direction of estimation effects: in 8-y-old boys, simplified NAE underestimated NAE . The reason for this is not quite clear. Possibly, the higher urinary output of OA in prepubertal boys than in prepubertal girls might have contributed to an elevated . Usually, children with similar body surface area have comparable urinary excretion of OA (34). Despite the fact that OA is mainly determined by anthropometric measures, there is also a dietary influence. Fruit can contain considerable amounts of aromatic OAs in the form of phenolic and benzoic acids. Unlike dietary OAs such as citrate, malate, and succinate, aromatic OAs are not metabolically oxidized to bicarbonate and water but are metabolically inactivated (detoxified) and excreted (mainly via the kidney) as acids, partly in the form of hippuric acid. Recently, 15 phenolic and benzoic acids were identified in cranberries, and phenolic acid was the most abundant (39). The additional acidifying effect of such plantderived OAs is not considered in our NAE estimation model and is probably one reason for the differences seen between estimated and analyzed OAs. Another source of inaccuracy stems from the fact that the sulfur content of different proteins varies, which certainly has an impact on the endogenously generated acidity
总体而言，包含钙的 NAE 在所有组中都低估了 NAE （大多数显着），而简化 和 PRAL（均不含钙）分别中度（大部分不显着）高估 和分析了 PRAL。这种统一的估计效应方向有一个例外：在 8 岁的男孩中，简化的 NAE 低估了 NAE 。其原因尚不清楚。青春期前男孩的尿量可能比青春期前的女孩高，这可能导致 .通常，具有相似体表面积的儿童具有相似的尿液OA排泄量（34）。尽管OA主要由人体测量学决定，但也有饮食影响。水果可以含有大量酚酸和苯甲酸形式的芳香OA。与枸橼酸盐、苹果酸盐和琥珀酸盐等膳食 OA 不同，芳香族 OA 不会被代谢氧化为碳酸氢盐和水，而是代谢失活（解毒）并以酸的形式排泄（主要通过肾脏），部分以马尿酸的形式排泄。最近，在蔓越莓中鉴定出15种酚酸和苯甲酸，其中酚酸含量最高（39）。在我们的 NAE 估计模型中未考虑此类植物来源的 OA 的额外酸化作用，这可能是估计和分析的 OA 之间存在差异的原因之一。另一个不准确的来源源于不同蛋白质的硫含量不同，这肯定会对内源性产生的酸度产生影响
resulting in sulfate. However, our formulas do not take this into account. A more differentiated PRAL model might have reduced the discrepancies seen between estimated and analyzed sulfate values in our children and adolescents. A correspondingly revised PRAL model should differentiate between certain foods or food groups, depending on the amount of sulfur per gram of protein.
生成硫酸盐。但是，我们的公式没有考虑到这一点。一个更加差异化的PRAL模型可能会减少我们的儿童和青少年的估计和分析硫酸盐值之间的差异。相应修订的PRAL模型应根据每克蛋白质的硫含量来区分某些食物或食物组。

Despite the fact that magnesium (similar to calcium) contributes only modestly to the base-forming potential of total mineral cations , and despite merely moderate correlations between dietary and urinary magnesium, it proves advantageous to leave this mineral in the NAE calculation formula for an appropriate prediction of . For the other dietary determinants of endogenous base and acid release, stronger correlations were observed between intakes and 24-h renal excretion rates. Correlation coefficients for potassium, phosphate, and sulfate ranged from 0.54 to 0.61 , which agreed fairly well with the associations seen in diet studies, in which potassium, phosphate, and nitrogen (analyzed in 24-h urine samples) were used as biomarkers to validate dietary intakes (40-42). Although the differences between the measured and the estimated urinary excretion values for the above minerals were mostly significant, the absolute mean differences were not so large and were within the range of our previously reported controlled-diet study in adults (18). This overall reasonable agreement and reproducibility emphasize the high degree of reliability of weighed dietary records of food intake in the children and adolescents in the present study. However, the weighed dietary record is not in common use in the United States or in many other countries. Moreover, food tables differ. Therefore, reproducibility of our findings on mineral and NAE prediction may vary according to the dietary assessment tools used.
尽管镁（类似于钙）对总矿物阳离子的碱形成潜力的贡献不大 ，尽管膳食镁和尿镁之间只有适度的相关性，但事实证明，将这种矿物质留在 NAE 计算公式中以适当预测是有利的 。对于内源性碱和酸释放的其他膳食决定因素，摄入量与 24 小时肾排泄率之间的相关性更强。钾、磷酸盐和硫酸盐的相关系数范围为 0.54 至 0.61，这与饮食研究中的相关性相当吻合，其中钾、磷酸盐和氮（在 24 小时尿液样本中分析）被用作验证饮食摄入量的生物标志物 （40-42）。尽管上述矿物质的测量值和估计尿排泄值之间的差异大多是显着的，但绝对平均差异并不大，并且在我们先前报道的成人控制饮食研究范围内（18）。这种总体合理的一致性和可重复性强调了本研究中儿童和青少年食物摄入量的称重饮食记录的高度可靠性。然而，称重饮食记录在美国或许多其他国家并不普遍使用。此外，食物餐桌也不同。因此，我们在矿物质和NAE预测方面的研究结果的可重复性可能因所使用的饮食评估工具而异。