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Estimation of net endogenous noncarbonic acid production in humans from diet potassium and protein contents
从饮食钾和蛋白质含量 估计人类内源性非碳酸净产量

Lynda A Frassetto, Karen M Todd, R Curtis Morris Jr, and Anthony Sebastian
琳达·弗拉塞托、凯伦·托德、小柯蒂斯·莫里斯和安东尼·塞巴斯蒂安

Abstract 抽象

Normal adult humans eating Western diets have chronic, low-grade metabolic acidosis, the severity of which is determined in part by the net rate of endogenous noncarbonic acid production (NEAP), which varies with diet. To prevent or reverse age-related sequelae of such diet-dependent acidosis (eg, bone and muscle loss), methods are needed for estimating and regulating NEAP. Because NEAP is difficult to measure directly, we sought a simple method to estimate it from diet-composition data. We focused on protein and potassium contents because the production of sulfuric acid from protein metabolism and bicarbonate from dietary potassium salts of organic acids are the major variable components of NEAP. Using steady state renal net acid excretion (RNAE) as an index of NEAP in 141 normal subjects eating 20 different diets, we found by multiple linear regression analysis that RNAE [mEq/d 10460 kJ diet (mEq/d 2500 kcal)] was predictable from protein [g/d 10460 kJ diet kcal); positive regression coefficient, and potassium diet ; negative regression coefficient, ] contents, which were not themselves correlated. Among diets, of the variation in RNAE could be accounted for by the ratio of protein (Pro) to potassium (K) content: RNAE Pro . Thus, by considering both the acidifying effect of protein and the alkalinizing effect of potassium (organic anions), NEAP can be predicted with confidence from the readily available contents of only 2 nutrients in foods. Provisionally, these findings allow estimation and regulation of NEAP through diet modification. Am J Clin Nutr 1998;68:576-83.
吃西餐的正常成年人患有慢性、低度代谢性酸中毒,其严重程度部分取决于内源性非碳酸产生 (NEAP) 的净速率,该速率随饮食而变化。为了预防或逆转这种饮食依赖性酸中毒的年龄相关后遗症(例如骨骼和肌肉流失),需要估计和调节NEAP的方法。由于NEAP很难直接测量,因此我们寻求一种简单的方法来从饮食成分数据中估计它。我们专注于蛋白质和钾含量,因为蛋白质代谢产生的硫酸和有机酸的膳食钾盐产生的碳酸氢盐是NEAP的主要可变成分。使用稳态肾净酸排泄 (RNAE) 作为 141 名正常受试者吃 20 种不同饮食的 NEAP 指标,我们通过多元线性回归分析发现 RNAE [mEq/d 10460 kJ 饮食 (mEq/d 2500 kcal)] 可预测蛋白质 [g/d 10460 kJ 饮食 kcal);正回归系数和 饮食 ;负回归系数, ]内容,其本身不相关。在饮食中, RNAE的变化可以通过蛋白质(Pro)与钾(K)含量的比率来解释:RNAE Pro 。因此,通过考虑蛋白质的酸化作用和钾(有机阴离子)的碱化作用,可以从食物中仅含有2种营养素的现成含量中可靠地预测NEAP。暂时,这些发现允许通过饮食调整来估计和调节NEAP。美国临床营养杂志 1998;68:576-83。

KEY WORDS Endogenous acid production, renal net acid excretion, potassium, protein, diet, metabolic acidosis
关键词 内源性酸产生, 肾净酸排泄, 钾, 蛋白质, 饮食, 代谢性酸中毒

INTRODUCTION 介绍

Normal adult humans eating typical American diets characteristically have chronic, low-grade metabolic acidosis (1-4). That persisting perturbation of systemic acid-base equilibrium occurs because metabolism of the diet releases noncarbonic acids into the systemic circulation (eg, sulfuric acid from metabolism of protein) in amounts that exceed the amounts of base released concomitantly (eg, bicarbonate from combustion of organic acid salts of potassium in vegetable foods) . The size of the discrepancy between acid and base production determines the net endogenous acid production rate (ie, the net acid load of the diet), which in turn determines the degree of perturbation of systemic acid-base equilibrium . Under normal physiologic circumstances, the net endogenous acid production rate and the degree of the attendant low-grade metabolic acidosis are determined primarily by the composition of the diet .
食用典型美国饮食的正常成年人通常患有慢性低代谢性酸中毒 (1-4)。系统酸碱平衡的持续扰动之所以发生,是因为饮食的新陈代谢将非碳酸释放到体循环中(例如,蛋白质代谢产生的硫酸),其量超过了伴随释放的碱的量(例如,植物性食物中钾的有机酸盐燃烧产生的碳酸氢盐) .酸和碱产之间的差异大小决定了内源性酸的净产酸率(即日粮的净酸负荷),这反过来又决定了全身酸碱平衡的扰动程度 。在正常生理情况下,净内源性酸产生率和随之而来的低度代谢性酸中毒的程度主要由饮食 的组成决定。
With advancing age, the severity of diet-dependent acidosis increases independently of diet . That occurs because kidney function ordinarily declines substantially with age, resulting in a condition similar to that of chronic renal insufficiency (7). Renal insufficiency induces metabolic acidosis by reducing conservation of filtered bicarbonate and excretion of acid. Failure to recognize the respective and independent roles of age-related impaired renal acid-base regulatory capacity and diet net acid load has until recently prevented the recognition that low-grade metabolic acidosis is characteristically present and worsens with age in otherwise healthy adults .
随着年龄的增长,饮食依赖性酸中毒的严重程度与饮食 无关。这是因为肾功能通常会随着年龄的增长而大幅下降,导致类似于慢性肾功能不全的病症(7)。肾功能不全通过减少过滤碳酸氢盐的保存和酸的排泄来诱导代谢性酸中毒。直到最近,由于未能认识到与年龄相关的肾酸碱调节能力受损和饮食净酸负荷的各自和独立作用,人们才认识到低级别代谢性酸中毒在其他方面健康的成年人 中具有特征性存在并随着年龄的增长而恶化。
The pathophysiologic implications of this chronic, low-grade, diet-dependent, age-amplified metabolic acidosis have been examined by determining the effects of neutralizing the net acid load of the diet with a dietary supplement of base, namely potassium bicarbonate. Potassium bicarbonate is a natural base that the body generates from the metabolism of organic acid salts of potassium (eg, potassium citrate) (8), whose density (ie, mmol food item) is greatest in fruit and vegetables. Long-term supplementation of the diet with potassium bicarbonate has numerous anabolic effects. In postmenopausal women for example, calcium and phosphorus balances improve (1), bone resorption markers decrease (1), bone formation markers increase (1), nitrogen balance improves (9), and serum growth hormone concentrations increase (10). These findings suggest that the adverse effects of chronic, low-grade, diet-dependent acidosis are not inconsequential and may contribute to such age-related disturbances as bone mass decline, osteoporosis, and muscle wasting.
这种慢性、低级别、饮食依赖性、年龄放大的代谢性酸中毒的病理生理学意义已经通过确定用碱膳食补充剂(即碳酸氢钾)中和饮食的净酸负荷的效果来检查。碳酸氢钾是人体从钾的有机酸盐(如柠檬酸钾)代谢中产生的天然碱(8),其密度(即mmol 食品)在水果和蔬菜中最大。长期补充碳酸氢钾具有许多合成代谢作用。例如,在绝经后妇女中,钙和磷平衡改善 (1),骨吸收标志物减少 (1),骨形成标志物增加 (1),氮平衡改善 (9),血清生长激素浓度增加 (10)。这些发现表明,慢性、低级别、饮食依赖性酸中毒的不良反应并非无关紧要,并且可能导致骨量下降、骨质疏松症和肌肉萎缩等与年龄相关的障碍。
One way to reduce or eliminate diet-dependent metabolic acidosis is by eating diets that impose little or no net acid load. Present methods for estimating the net acid load from the composition of the diet require a detailed inventory of nutrient composition and estimates of the gastrointestinal absorption rates of the nutrients; these methods have been validated for only a few diets (11, 12). In vivo methods for quantifying net endogenous acid production are complex and labor intensive (5) and are suitable only for specialized clinical research centers. Accordingly, simple dietary guidelines for quantifying and regulating endogenous acid production rates do not exist. In this paper we present a new method for estimating the net acid load of the diet from readily available information on diet composition, specifically total protein and potassium contents. We focused on these 2 components because the rate of sulfuric acid production from protein metabolism and the rate of bicarbonate generation from metabolism of intestinally absorbed potassium salts of organic acids are major and highly variable components of the net endogenous acid production rate . This paper describes the empirically derived relations between these 2 components in different diets and how they can be used to predict net endogenous acid production.
减少或消除饮食依赖性代谢性酸中毒的一种方法是吃摄入很少或没有净酸负荷的饮食。目前从饮食成分中估计净酸负荷的方法需要详细的营养成分清单和营养素的胃肠道吸收率估计;这些方法仅在少数饮食中得到验证(11,12)。用于定量内源性酸净产量的体内方法复杂且劳动密集型 (5),仅适用于专门的临床研究中心。因此,量化和调节内源性酸产生率的简单膳食指南并不存在。在本文中,我们提出了一种新方法,用于根据饮食成分的现成信息,特别是总蛋白质和钾含量来估计饮食的净酸负荷。我们之所以关注这两个成分,是因为蛋白质代谢产生的硫酸速率和肠道吸收的有机酸钾盐代谢产生的碳酸氢盐的速率是净内源性酸产生速率 的主要且高度可变的成分。本文描述了这两种成分在不同饮食中的经验推导关系,以及如何利用它们来预测内源性酸的净产生。

SUBJECTS AND METHODS 主题和方法

For this study of normal subjects, we used the steady state rate of renal net acid excretion (RNAE) as an index of the net rate of endogenous noncarbonic acid production (NEAP) . We measured RNAE in 42 subjects, each of whom ate 1 of 6 different whole-food diets while residing in the University of California, San Francisco (UCSF) General Clinical Research Center. In addition, we obtained values of RNAE from the literature for 99 subjects eating of 14 whole-food diets for which pertinent data on nutrient composition were reported (5, 11-15). In some cases the same subjects were restudied while ingesting a second or third diet (5, 11, 13-15). Data were accumulated for 20 different whole-food diets ingested by 141 different subjects, reflecting a total of 199 subject-diet combinations. All subjects ingested a diet for , a period previously shown to be sufficient for establishing a steady state of acid-base equilibrium (2). Selected articles provided at minimum data on diet protein, potassium, and energy contents. We excluded articles in which diets were supplemented with mineral salts because such salts typically supply acid or base equivalents.
对于正常受试者的这项研究,我们使用肾脏净酸排泄的稳态速率 (RNAE) 作为内源性非碳酸产生净速率 (NEAP) 的指标。我们测量了 42 名受试者的 RNAE,他们每个人在加州大学旧金山分校 (UCSF) 综合临床研究中心居住期间吃了 6 种不同的全食物饮食中的 1 种。此外,我们从文献中获得了 99 名食用 14 种全食物饮食的受试者的 RNAE 值,这些饮食报告了有关营养成分的相关数据 (5, 11-15)。在某些情况下,在摄入第二或第三饮食时重新研究了相同的受试者(5,11,13-15)。积累了 141 名不同受试者摄入的 20 种不同全食物饮食的数据,总共反映了 199 种受试者饮食组合。所有受试者都摄入了一段饮食, 这段时间先前被证明足以建立酸碱平衡的稳定状态 (2)。选定的文章提供了关于饮食蛋白质、钾和能量含量的最低限度数据。我们排除了饮食中补充矿物盐的文章,因为这些盐通常提供酸或碱当量。

Subjects 科目

The subjects were healthy men and women. Subjects participating in the UCSF General Clinical Research Center studies signed informed consent documents as specified by the university's committee on human research. The subjects ranged in age from 17 to [data on age are lacking for 8 subjects in one article (5)].
受试者是健康的男性和女性。参与加州大学旧金山分校综合临床研究中心研究的受试者签署了该大学人类研究委员会规定的知情同意书。受试者的年龄从17岁到 [一篇文章(5)中缺少8名受试者的年龄数据]。

Diets 饮食

Values for protein, potassium, and energy contents were extracted from the available data for the 20 diets ingested by the 141 subjects included in the analysis. For the 6 diets ingested by the subjects studied in the UCSF General Clinical Research Center, we determined the content of those nutrients either by direct chemical analysis or from diet-composition tables (16). In some of the papers cited, the nutrient content was determined from chemical analysis of the diet ; in others, it was estimated by using specific diet-composition tables cited by the authors .
蛋白质、钾和能量含量的值是从分析中包含的 141 名受试者摄入的 20 种饮食的可用数据中提取的。对于在加州大学旧金山分校综合临床研究中心研究的受试者摄入的 6 种饮食,我们通过直接化学分析或饮食成分表确定了这些营养素的含量 (16)。在引用的一些论文中,营养成分是通过饮食 的化学分析确定的;在其他情况下,它是通过使用作者 引用的特定饮食组成表来估计的。
For 13 diets sufficient information was available for separately estimating the protein contents of the animal and vegetable foods of the diet or by using Agriculture Handbook no. 8 (16) as modified by chemical analyses of certain food items used by the UCSF General Clinical Research Center. For those 13 diets we also estimated sulfur content from the methionine and cystine contents of the listed food items (16). Sulfur content was computed from the formula
对于13种饮食,有足够的信息来单独估计饮食 中动物和植物性食物的蛋白质含量,或者使用农业手册第8(16)号,该手册通过对加州大学旧金山分校综合临床研究中心使用的某些食品进行化学分析而修改。对于这 13 种饮食,我们还从所列食物的蛋氨酸和胱氨酸含量中估计了硫含量 (16)。根据公式计算硫含量
where 149.2 is the molecular weight of methionine and 240.3 that of cystine. For 3 additional diets such estimation was not possible because a detailed listing of food items was lacking, but sulfur contents were specified by the investigators (13). Thus, sulfur contents were available for a total of 16 diets.
其中 149.2 是蛋氨酸的分子量,240.3 是胱氨酸的分子量。对于另外 3 种饮食,由于缺乏详细的食物清单,因此无法进行这种估计,但研究人员指定了硫含量 (13)。因此,总共有16种饮食的硫含量。
For 16 diets, sufficient data were available to calculate the difference between the inorganic cations and anions of the diet, namely , expressed in milliequivalents. A positive value for the difference (ie, an excess of inorganic cations, or an anion gap) implies that the diet contains an excess of organic anions (eg, citrate) relative to organic cations (eg, lysine), which fills the anion gap. Because metabolism of organic anions yields base equivalents and that of organic cations yields acid equivalents, this difference can be taken as the potential base of the diet. Negative values of potential base are theoretically possible but are uncommon for ordinary diets. Because the and contents of table salt are equal and because the contents of the 2 ions in natural foods are equal on average (17), we omitted the mutually canceling terms and in the calculation. That allowed calculation of potential base for diets in which the content was not specified.
对于16种日粮,有足够的数据来计算日粮中无机阳离子和阴离子之间的差异,即 以毫当量表示。差异的正值(即无机阳离子过量或阴离子间隙)意味着饮食中含有相对于有机阳离子(如赖氨酸)过量的有机阴离子(例如柠檬酸盐),有机阳离子填充了阴离子间隙。由于有机阴离子的代谢产生碱当量,而有机阳离子的代谢产生酸当量,因此这种差异可以作为饮食的潜在基础。理论上,潜在碱的负值是可能的,但在普通饮食中并不常见。由于食盐 的 和 含量相等,并且天然食品中 2 个离子的含量平均相等 (17),因此我们在计算中省略了相互抵消项 。这样就可以计算出未指定 含量的饮食的潜在基础。

Data analysis 数据分析

For analysis of the relation of diet protein content, potassium content, and NEAP, the values for those variables were first collected into a master database comprising the individual values of those variables available for each subject. For the articles that failed to report values for individual subjects , only the subject-group average was included. As a result, the master database contains individual subject data for 56 subjects and subject-group average data for 85 subjects, yielding a total of 73 data points. From the master database, a working database was developed comprising the average values of the selected variables for each group of subjects ingesting each diet, yielding a total of 20 data points, 1 for each of the 20 diets.
为了分析饮食蛋白质含量、钾含量和NEAP之间的关系,首先将这些变量的值收集到一个主数据库中,该数据库包含每个受试者可用的这些变量的单个值。对于未能报告单个受试者 值的文章,仅包括受试者组平均值。因此,主数据库包含 56 名受试者的个体受试者数据和 85 名受试者的受试者组平均数据,总共产生 73 个数据点。从主数据库中,开发了一个工作数据库,其中包含摄入每种饮食的每组受试者的选定变量的平均值,总共产生 20 个数据点,20 种饮食中每组 1 个。
Because NEAP for subjects eating the same diet varies depending on the quantity ingested, most of the data analysis was carried out on values of NEAP adjusted to a standard quantity of diet ingested, expressed as energy intake, namely 10460 , a convenient reference value and one that was close to the average energy intake [10033 kJ/d (2398 kcal/d)] of the 141 subjects studied.
由于吃相同饮食的受试者的 NEAP 因摄入量而异,因此大多数数据分析是针对调整为摄入的标准饮食量的 NEAP 值进行的,表示为能量摄入量,即 10460 ,一个方便的参考值,并且接近 141 名研究受试者的平均能量摄入量 [10033 kJ/d (2398 kcal/d)]。

Laboratory analysis 实验室分析

RNAE, expressed as , was determined as the sum of the excretion rates of titratable acid and ammonium minus that of
RNAE,表示为 ,被确定为可滴定酸和铵的排泄率之和减去
TABLE 1 表1
Mean protein, potassium, and renal net acid excretion data for each
每种 药物的平均蛋白质、钾和肾脏净酸排泄数据
Diet
code
Energy
intake
Potassium
intake
Protein
intake
RNAE Pro/K
1 7113 80 75 12 0.94
2 9121 133 60 24 0.45
3 7113 74 75 26 1.01
4 9293 99 74 31 0.75
5 7657 40 39 32 0.96
6 8736 72 85 37 1.19
7 7113 72 75 39 1.04
8 13104 56 60 40 1.06
9 13598 75 90 45 1.21
10 10962 75 78 47 1.04
11 13765 93 114 53 1.23
12 15803 73 93 62 1.27
13 10343 85 99 64 1.17
14 10209 101 95 70 0.94
15 12636 98 100 70 1.02
16 8364 41 90 71 2.19
17 8527 58 96 75 1.64
18 9247 40 79 102 1.98
19 14891 124 193 115 1.56
20 9037 54 120 136 2.21
RNAE, renal net acid excretion; Pro, protein in g/d; K, potassium in ; Pro/K, ratio of Pro to K.
RNAE,肾净酸排泄;Pro,蛋白质,单位:g/d;K, 钾含量 ;Pro/K,Pro与K的比值。
bicarbonate. In our laboratory, the urine bicarbonate concentration was calculated from the measured values of urine and carbon dioxide content by use of the Henderson-Hasselbach equation, for which the solubility coefficient of carbon dioxide was taken as 0.0309 and was corrected for ionic strength: , where and concentrations are expressed in Eq/L. Urine total carbon dioxide content was determined by thermal conductivity. Titratable acid concentration was determined by titration, and urine ammonium concentration was determined by the phenol method (18). In the articles from the literature surveys, RNAE was calculated as described above from component assays as described in the respective articles (5, 11-15).
碳酸氢盐。在我们的实验室中,尿碳酸氢盐浓度是使用 Henderson-Hasselbach 方程根据尿液 和二氧化碳含量的测量值计算得出的,其中二氧化碳的溶解系数为 0.0309,并 针对离子强度进行校正: ,其中 浓度以方程/L 表示。 尿液总二氧化碳含量由导热系数确定。通过滴定法测定可滴定酸浓度,通过苯酚法测定尿铵浓度 (18)。在文献调查的文章中,如上所述,从相应文章中描述的组分测定中计算 RNAE (5, 11-15)。

Units of measure 计量单位

Charged species are expressed in milliequivalents to allow calculation (by algebraic summation) of charge balances (ie, estimation of cation or anion gaps) necessary for conclusions about dietary potential acid or base content. The number of milliequivalents of a charged species is equal to the number of millimoles multiplied by the charge valance of the species. There is no SI unit for net acid; the standard units of milliequivalents are used throughout.
带电物质以毫当量表示,以便计算(通过代数求和)电荷平衡(即阳离子或阴离子间隙的估计),以得出有关膳食潜在酸或碱含量的结论。带电物质的毫当量数等于毫摩尔数乘以该物质的电荷价。净酸没有国际单位制单位;自始至终都使用毫当量的标准单位。

Statistical analysis 统计分析

Statistical analyses were carried out with SIGMASTAT (Jandel Corp, San Rafael, CA).
与SIGMASTAT(Jandel Corp,San Rafael,CA)一起进行统计分析。

RESULTS 结果

The subject-group averages for the 20 diets analyzed are summarized in Table 1. In the 20 diets, protein content ranged from 39 to , potassium content from 40 to , energy
表1总结了所分析的20种饮食的受试者组平均值。在20种饮食中,蛋白质含量从39到 40不等,钾含量从40到 40不等

TABLE 2 表2
Regression analyses for 20 diets
20种饮食 的回归分析
Potassium Protein Pro/K
RNAE
-0.440 - - - - -
-0.374 - - 0.14 -0.37 NS
NS - - - -
RNAE
0.792 - - -
- 0.597 - 0.36 0.69 0.006
- - -
RNAE
-0.614 -0.937 -
-0.522 -0.707 - 0.62
- - - -
RNAE
- - 62.1 0.71 0.84
- - - - -
, nonstandardized regression coefficient; B, standardized regression coefficient; horizontal rows of values indicate the levels of significance of the regression coefficients. Protein (Pro, in g) and potassium (mEq) are in units/d per (2500 kcal) diet. RNAE, renal net acid excretion.
、非标准化回归系数;B, 标准化回归系数; 值的水平行表示回归系数的显著性水平。蛋白质(Pro,单位:g)和钾(mEq)以单位/天为单位 (2500 kcal)饮食。RNAE,肾净酸排泄。
content from 7113 to (1700 to ), and RNAE from 12 to . Expressed in units per day per diet ingested, the corresponding ranges were similar: protein content, 48-139 g; potassium content, 45-153 mEq; and RNAE, 18-157 mEq. The energy-adjusted values of both protein and potassium contents were normally distributed (KolmogorovSmirnov test). The ratio of protein to potassium content varied over a 5 -fold range, from 0.45 to . There was no significant correlation between protein content and potassium content among diets.
含量从 7113 到 (1700 到 ),RNAE 从 12 到 。以每天摄入的每种 饮食的单位表示,相应的范围相似:蛋白质含量,48-139克;钾含量,45-153 mEq;和 RNAE,18-157 mEq。蛋白质和钾含量的能量调整值均呈正态分布(KolmogorovSmirnov检验)。蛋白质与钾含量的比例变化为5倍,从0.45到 。饮食中蛋白质含量和钾含量之间没有显著相关性。
By multiple linear regression analysis of the energy-adjusted variables (Table 2), protein content and potassium content were independent predictors of RNAE (Figure 1; ):
通过能量调整变量的多元线性回归分析(表2),蛋白质含量和钾含量是RNAE的独立预测因子(图1; ):
RNAE Pro
RNAE 专业版
where Pro is protein.
其中 Pro 是蛋白质。
That is, the regression coefficients of both protein and potassium were significantly different from zero, and 0.003 , respectively. The regression coefficient of protein was positive and that of potassium was negative, suggesting that increasing protein content increases RNAE and increasing potassium content decreases it. Differences in protein content had a slightly greater (1.4-fold) effect on RNAE than did differences in potassium content, as indicated by the values of their respective standardized regression coefficients, namely, 0.71 compared with -0.52 (Table 2).
也就是说,蛋白质和钾的回归系数分别从零 0.003显著不同。蛋白质的回归系数为正,钾的回归系数为负,表明蛋白质含量增加可增加RNAE,增加钾含量可降低RNAE。蛋白质含量的差异对RNAE的影响略大于钾含量的差异(1.4倍),如其各自标准化回归系数的值所示,即0.71与-0.52(表2)。
Similar results were obtained when the regression was performed without adjusting the 3 variables to a constant energy content :
在不将 3 个变量调整为恒定能量含量 的情况下进行回归时,也获得了类似的结果:
RNAE Pro
RNAE 专业版
Both regression coefficients were significantly different from zero, and , respectively. Differences in protein content had a 1.9-fold greater effect on RNAE than did differences in potassium content, as indicated by the values of their respective standardized regression coefficients, 0.88 compared with -0.46 .
两个回归系数分别与零 、 显著不同。蛋白质含量差异对RNAE的影响是钾含量差异的1.9倍,如其各自的标准化回归系数值所示,0.88与-0.46相比。
FIGURE 1. The relation between steady state renal net acid excretion (RNAE) and dietary contents of protein (Pro) and potassium for 20 different whole-food diets. RNAE Pro . The regression coefficients of both Pro and were significantly different from zero, and , respectively.
图 1.20 种不同全食物饮食的稳态肾净酸排泄 (RNAE) 与蛋白质 (Pro) 和钾膳食含量之间的关系。RNAE 专业 版。Pro 和 的回归系数分别与零 、 显著不同。
Because protein and potassium contents were directionally opposing independent predictors of RNAE by multiple linear regression analysis, the ratio of protein to potassium content in the diet should provide a good linear index of RNAE. Thus, by linear regression analysis, RNAE (mEq/d 10460 kJ diet) correlated significantly with Pro/K (g/mEq) (Table 2, Figure 2; :
由于蛋白质和钾含量在多元线性回归分析中是 RNAE 的方向性相反的独立预测因子,因此饮食中蛋白质与钾含量的比率应提供良好的 RNAE 线性指数。因此,通过线性回归分析,RNAE(mEq/d 10460 kJ饮食)与Pro/K(g/mEq)显著相关(表2,图2;
Similar results were obtained when the variables were not energy adjusted :
当变量未进行能量调整 时,也获得了类似的结果:
For the subset of 13 diets for which data for both animal and vegetable foods were available, RNAE was highly correlated with animal protein content but not with vegetable protein content. The range of variation of vegetable protein content ( diet; minimum and maximum: 18 and ] was much less than that of animal protein content (104 g/10460 kJ of diet; minimum and maximum: 13 and ), a nearly 3-fold difference. Expressing vegetable food intake in terms of energy ingested likewise did not give a significant correlation with RNAE. The ratio of animal to vegetable protein content of the 13 diets varied from 0.23 to 4.31, a nearly 20 -fold range, and the individual values for animal and vegetable protein contents varied independently for the diets, as did animal and vegetable energy ingested.
对于可获得动物和植物性食物数据的 13 种饮食的子集,RNAE 与动物蛋白含量 高度相关,但与植物蛋白含量无关。植物蛋白含量的变化范围( 日粮;最小值和最大值:18和 ]远小于动物蛋白含量(104 g/10460 kJ日粮;最小值和最大值:13和 ),相差近3倍。同样,以摄入的能量来表示植物性食物摄入量与RNAE没有显着相关性。13种日粮的动植物蛋白含量比例从0.23到4.31不等,相差近20倍,动物和植物蛋白含量的个体值因日粮而异,动物和植物蛋白含量的摄入量也随日粮的变化而变化。
In the subset of 16 diets for which data for sulfur content were available, RNAE correlated directly with sulfur content ( ; Table 3). Sulfur content in turn correlated directly with total protein ( diets; diets) and with animal protein ( diets). (Correlations for both and diets are reported to allow comparison of the relation of sulfur content with both total and animal protein contents because total protein content was known for all diets but animal protein content for only 13 diets.)
在有硫含量数据的16种饮食中,RNAE与硫含量直接相关( ;表3)。硫含量反过来又与总蛋白质( 饮食; 饮食)和动物蛋白( 饮食)。(据报道,两者 饮食的相关性允许比较硫含量与总蛋白和动物蛋白含量的关系,因为所有饮食的总蛋白质含量都是已知的,但只有 13 种饮食的动物蛋白含量。
In the subset of 16 diets for which data were available to calculate potential base content, potential base varied from -2 to diet. RNAE correlated inversely with potential base ( ), and potential base in turn correlated directly with potassium content . By multiple regression analysis, potential base and protein content together accounted for of the variation in RNAE (