Friedrich Manz

Potential renal acid load of foods and its influence on urine pH

The purpose of this study was to calculate the potential renal acid load (PRAL) of selected, frequently consumed foods. A physiologically based calculation model was recently validated to yield an appropriate estimate of renal net acid excretion (NAE); the model depends primarily on nutrient intake data. When nutrient data from actual food composition tables were used, the calculation model yielded PRAL values that ranged from an average maximum of 23.6 mEq/100 g for certain hard cheeses over 0 mEq/100 g for fats and oils to an average minimum of approximately -3 mEq/100 g for fruits and fruit juices and vegetables. By means of these PRAL data (summed according to the amounts of foods and beverages consumed daily and by an estimate of excretion of organic acids [based on body size]), the daily NAE can be calculated. This calculation methodology, primarily based on PRAL, allows an appropriate prediction of the effects of diet on the acidity of urine. For practical applicability in dietetic prevention of recurrent urolithiasis or in other fields of dietetics, the additionally determined correlation (r = .83; P < .001) between NAE and urine pH can be used to ascertain NAE target values for a desired urine pH modification.

Bone Mineral Content per Muscle Cross‐Sectional Area as an Index of the Functional Muscle‐Bone Unit

Bone densitometric data often are difficult to interpret in children and adolescents because of large inter‐ and intraindividual variations in bone size. Here, we propose a functional approach to bone densitometry that addresses two questions: Is bone strength normally adapted to the largest physiological loads, that is, muscle force? Is muscle force adequate for body size? To implement this approach, forearm muscle cross‐sectional area (CSA) and bone mineral content (BMC) of the radial diaphysis were measured in 349 healthy subjects from 6 to 19 years of age (183 girls), using peripheral quantitative computed tomography (pQCT). Reference data were established for height‐dependent muscle CSA and for the variation with age in the BMC/muscle CSA ratio. These reference data were used to evaluate results from three pediatric patient groups: children who had sustained multiple fractures without adequate trauma (n = 11), children with preterminal chronic renal failure (n = 11), and renal transplant recipients (n = 15). In all three groups mean height, muscle CSA, and BMC were low for age, but muscle CSA was normal for height. In the multiple fracture group and in renal transplant recipients the BMC/muscle CSA ratio was decreased (p < 0.05), suggesting that bone strength was not adapted adequately to muscle force. In contrast, chronic renal failure patients had a normal BMC/muscle CSA ratio, suggesting that their musculoskeletal system was adapted normally to their (decreased) body size. This functional approach to pediatric bone densitometric data should be adaptable to a variety of densitometric techniques.

The Development of Metaphyseal Cortex—Implications for Distal Radius Fractures During Growth

Fractures of the distal radial metaphysis are very common in otherwise healthy children. The reasons for this high fracture incidence are not entirely clear. To address this problem, we undertook a detailed analysis of distal radius development using peripheral quantitative computed tomography (pQCT) at a site 4% proximal to the radial articular surface. The study population comprised 337 healthy children and adolescents (aged 6‐18 years; 171 girls) and 107 adults (aged 29‐40 years; 88 women). Total volumetric bone mineral density (vBMD) remained stable at about 70% of the adult value between the ages of 6‐7 years and 14‐15 years in both genders. Cortical thickness increased little between 6‐7 years and 12‐13 years in girls and 14‐15 years in boys. Strength‐Strain Index (SSI; a parameter combining geometry and density) was still at only 20% of the adult value in girls aged 10‐11 years and at 21% of the adult level in boys aged 12‐13 years. At these ages, factors that contribute to the mechanical challenge to the distal radius in case of a fall (forearm length and body weight) had already reached 49% and 36% of the adult value in girls and boys, respectively. The shaping of the distal radius cortex (metaphyseal inwaisting) was assessed by analyzing the decrease in cross‐sectional bone size between adjacent bone slices in a separate population of 44 children (aged 8‐19 years; 26 girls). The rates of periosteal resorption and endocortical apposition were estimated to average 8 μm/day and 10 μm/day, respectively, during the growth period. In conclusion, during growth the increase in distal radius strength lags behind the increase in mechanical challenges caused by a fall, because metaphyseal cortical thickness does not increase sufficiently. The endocortical apposition rate is already very high at that site and apparently cannot be further increased to levels that would be necessary to keep bone strength adapted to the mechanical requirements.

Muscle Analysis by Measurement of Maximal Isometric Grip Force: New Reference Data and Clinical Applications in Pediatrics

Skeletal muscle development is one of the key features of childhood and adolescence. Determining maximal isometric grip force (MIGF) using a hand-held Jamar dynamometer is a simple method to quantify one aspect of muscle function. Presently available reference data present MIGF as a function of chronological age. However, muscle force is largely determined by body size, and many children undergoing muscle performance tests in the clinical setting suffer from growth retardation secondary to a chronic disorder. Reference data were established from simple regressions between age or log height and log MIGF in a population of 315 healthy children and adolescents aged 6 to 19 y (157 girls). These data were used to calculate age- or height-dependent SD scores (SDS) for MIGF in three pediatric patient groups. In renal graft recipients (n = 14), the age-dependent MIGF SDS was markedly decreased (−2.5 ± 1.9; mean ± SD). However, these patients had short stature (height SDS, −2.5 ± 1.2), and the height-dependent MIGF SDS was close to normal (−0.4 ± 1.5). Similarly, in cystic fibrosis patients (n = 13) age-dependent MIGF SDS was −1.6 ± 1.6, but height-dependent MIGF SDS was −0.5 ± 1.1. Children with epilepsy who were taking anticonvulsant therapy (n = 34) had normal stature, and consequently age- and height-dependent MIGF SDS were similar (0.4 ± 1.0 and 0.4 ± 0.8, respectively). In conclusion, MIGF determination provides information on an important aspect of physical development. Height should be taken into account to avoid misinterpretation.

Energy intake of 1 to 18 year old German children and adolescents.

In a sample of 695 healthy well-nourished German children and adolescents covering the total age range from 1 to 18 years, 3d weighed diet records were collected and measurements of body height and weight were taken. 10% non-plausible records (reported energy intake (EI):estimated basal metabolic rate (BMR) < Cut off 1.06) were excluded from further analysis. The rate of non-plausible records was low in the childhood age groups (2-6%), higher in the male (10%), and highest in the female adolescents (30%). Recalculation of age and sex specific cut offs based on assumed light physical activity levels (PAL) reduced the exclusion rate to 6.5% (total) and 20% (female adolescents). The reported energy intake of the total sample based on plausible records (n = 627, EI:BMR > or = 1.06) was close to the new estimations of energy requirements assuming light physical activity which are proposed for the revision of the current FAO/WHO energy requirements. The sample was of normal height and weight compared to the Netherlands growth references. For a definite interpretation of the low reported energy intake in the context of health promoting physical activity patterns of children and adolescents more scientific evidence should be available.

Macronutrient Intake of 3- to 36-Month-Old German Infants and Children: Results of the DONALD Study

The intake of macronutrients (protein, fat, fatty acids, carbohydrates, added sugars, fiber) was assessed in 354 healthy German infants and children aged 3–36 months from 3-day weighed diet records. The intake of protein ranged between 7 and 14% of energy intake. Fat intake decreased from 3 months (breast-fed boys and girls, 48%; formula-fed boys/girls, 41/44%) to 12 months (boys/girls, 33/36%) due to the increasing consumption of commercial weaning foods, and then increased again up to 36 months (boys/girls, 40/43%). Intake of added sugars decreased during the first 12 months and then increased again, but only slightly exceeded the limit of 10%. Intake of dietary fiber was highest at the age of 1 year (boys/girls, 2.7/2.3 g/MJ). The macronutrient intake was in accordance with other German and European surveys, but deviated considerably from the respective recommendations.

Energy and nutrient dietary reference values for children in Europe: methodological approaches and current nutritional recommendations.

The Expert Group on the Methodological Approaches and Current Nutritional Recommendations in Children and Adolescents was convened to consider the current situation across Europe with regard to dietary recommendations and reference values for children aged 2-18 years. Information was obtained for twenty-nine of the thirty-nine countries in Europe and a comprehensive compilation was made of the dietary recommendations current up to September 2002. This report presents a review of the concepts of dietary reference values and a comparison of the methodological approaches used in each country. Attention is drawn to the special considerations that are needed for establishing dietary reference values for children and adolescents. Tables are provided of the current dietary reference values for energy and for the macronutrients, vitamins, minerals, trace elements and water. Brief critiques are included to indicate the scientific foundations of the reference values for children and to offer, where possible, an explanation for the wide differences that exist between countries. This compilation demonstrated that there are considerable disparities in the perceived nutritional requirements of European children and adolescents. Although some of this diversity can be attributed to real physiological and environmental differences, most is due to differences in philosophy about the best methodological approach to use and in the way the theoretical approaches are applied. The report highlights the main methodological and technological issues that will need to be resolved before harmonization can be fully considered. Solving these issues may help to improve the quality and consistency of dietary reference values across Europe. However, there are also considerable scientific and political barriers that will need to be overcome and the question of whether harmonization of dietary reference values for children and adolescents is a desirable or achievable goal for Europe requires further consideration.

Fruit juice consumption and the prevalence of obesity and short stature in german preschool children : Results of the DONALD study

BACKGROUND In recent years, a possible association between excessive consumption of fruit juice (> or =12 fl oz per day) and short stature and/or obesity has been discussed. The association among the consumption of fruit juice, anthropometric indices, and the overall diet was examined during a 3-year period in a sample of healthy preschool children participating in the Dortmund Nutritional and Anthropometrical Longitudinally Designed (DONALD) Study. METHODS Two hundred five children were examined annually at the ages of 3, 4, and 5 years. Dietary intake was calculated from 3-day weighed diet records. Height was measured using a stadiometer. Weight was measured using an electronic scale. RESULTS Five children consumed excessive fruit juice continually in all three records, 10 children in two records, and 23 children in one record. None of the five children with repeatedly excessive fruit juice consumption was obese or short. Growth velocity, body mass index, and height standard deviation score were not correlated with fruit juice consumption. Consumption of fruit juice was inversely correlated with the consumption of all other beverages and the total consumption of all other food. The intake of protein, fat, and carbohydrates of children consuming excessive fruit juice was closer to the international dietary preventive guidelines than the intake of children consuming low amounts of fruit juice. CONCLUSIONS In the study sample, even repeatedly excessive fruit juice consumption had no influence on anthropometric indices. The results do not justify a general warning or a general promotion regarding high fruit juice consumption in preschool childrens diets.

Urinary calcium excretion in healthy children and adolescents

Abstract Urinary calcium (Ca) excretion was determined in 1,578 24-h urine samples from 507 healthy children and adolescents (252 boys, 255 girls; 2.8–18.4 years) participating in the DONALD Study and is presented for 32 different age and sex groups. Calciuria values related to body weight (mg/kg per day) were relatively constant except for a transient decrease during puberty in all centiles, with a later onset in boys than girls. Distribution of calciuria (mg/kg per day) was best normalized by log transformation, with an almost constant standard deviation of the log-transformed values. Ca excretion was ≥4 mg/kg per day in 8.6% and ≥6 mg/kg per day in 1.5% of the urine samples. Based on Ca excretion rates of 1,080 pairs of 24-h urine samples from 364 children and adolescents, sensitivity, specificity, and the predictive value for hypercalciuria (≥4 mg/kg per day) in the next urine sample were calculated at three test levels classifying calciuria of the initial urine sample. In summary, this study presents normal values of urinary Ca excretion related to age and sex in a population of healthy German children and adolescents consuming a typical western-style diet. A high level of calciuria in a random urine sample is important in the diagnosis of hypercalciuria.

Quantification of iodine supply: representative data on intake and urinary excretion of iodine from the German population in 1996.

Background/Methods: In Germany, iodine deficiency is common. In a representative group of 2,500 Germans (age >13 years), using a specially designed food questionnaire, the iodine intake was calculated. In addition, iodine and creatinine concentrations in spot urine samples were determined in three groups with a possibly increased risk of iodine deficiency (769 conscripts, 886 pairs of mothers and newborns) or future hyperthyroidism (574 adults, age range 50–70 years) from 26 representative regions. In four groups of controls (young and older male and female adults; n = 91), 24-hour urine iodine and creatinine were measured in six diurnal fractions to calculate group- and period-specific factors for the estimation of the 24-hour iodine excretion from data of iodine/creatinine ratio and time of micturition in spot urine samples. Results: The mean calculated iodine intake (excretion) was 119 µg/day for the group of Germans above 13 years; it was 119 µg/day (125 µg/day) for adults aged 50–70 years, 137 µg/day (125 µg/day) for conscripts, and 162 µg/day for breast-feeding mothers. The median iodine concentration (iodine/creatinine ratio) was 9.4 µg/dl (83 µg/g) in 566 adults aged 50–70 years, 8.3 µg/dl (57 µg/g) in 772 conscripts. and 5.6 µg/dl (156 µg/g) in 739 breast-fed newborns. Conclusions: Compared to older data, the iodine intake in Germany has increased. In 1996, the meticulously quantified average deficit was about 30% of the recommended iodine intake.