Examination of iodine status in the German population: an example for methodological pitfalls of the current approach of iodine status assessment.

PURPOSE: Preliminary iodine concentration (UIC) measurements in spot urines of the representative German adult study DEGS indicated a severe worsening of iodine status compared to previous results in German children (KiGGS study). Therefore, we aimed to evaluate adult iodine status in detail and to investigate the impact of hydration status on UIC. METHODS: UIC and creatinine concentrations were measured in 6978 spot urines from the German nationwide DEGS study (2008-2011). Twenty-four-hour iodine excretions (24-h UIE) were estimated by relating iodine/creatinine ratios to age- and sex-specific 24-h creatinine reference values. Urine osmolality was measured in two subsamples of spot urines (n = 100 each) to determine the impact of hydration status on UIC. RESULTS: In DEGS, median UIC was 69 µg/L in men and 54 µg/L in women, lying clearly below the WHO cutoff for iodine sufficiency (100 µg/L). Estimated median 24-h UIE was 113 µg/day, accompanied by 32 % of DEGS adults, lying below the estimated average requirement (EAR) for iodine. Comparative analysis with the KiGGS data (>14,000 spot urines of children; median UIC 117 µg/L) revealed a comparable percentage

Current daily salt intake in Germany: biomarker-based analysis of the representative DEGS study.

PURPOSE: A high dietary salt intake is a serious risk factor for the development of hypertension. Daily salt intake in most of the European countries substantially exceeds the current recommendations of salt intake. For Germany, so far, no valid biomarker-based data on current daily salt intake are available. METHODS: Data basis for this biomarker-based estimation of salt intake in the German population was the representative DEGS Study (German Health Interview and Examination Survey for Adults) conducted 2008-2011 in 18-79 old adults living in Germany. Daily salt intake was estimated from 6,962 sodium and creatinine measurements in spot urine samples. RESULTS: Median estimated daily salt intake of the 18-79 olds was 10.0 g in men and 8.4 g in women. More than 75% of men and about 70% of women exceeded the current recommendation of a maximum salt intake of 6 g/day. Fifty percentage of men and more than 35% of the women had a daily salt intake >10 g. CONCLUSION: Daily salt intake of the German population considerably exceeds the current recommendation to eat no more than 6 g salt per day. A general reduction of salt content in processed foods-which are currently the main source of salt intake-offers a promising and cost-effective potential for the improvement of all salt intake-dependent health outcomes in the population.

[The DONALD cohort. An updated overview on 25 years of research based on the Dortmund Nutritional and Anthropometric Longitudinally Designed study]. / Die DONALD Kohorte. Ein aktueller Überblick zu 25 Jahren Forschung im Rahmen der Dortmund Nutritional and Anthropometric Longitudinally Designed Study.

The DONALD study has been conducted in Dortmund, Germany since 1985 to examine the complex relations between nutritional intake, metabolism and growth from infancy to adulthood. Every year, approximately 40 infants are newly recruited into the open cohort study. Examinations conducted at ages 3, 6, 9, 12, 18, 24 months and then annually until young adulthood, comprise anthropometry, a 3 day weighed dietary record, a 24 h urine sample (from age 3-4 years onwards), medical examinations and parental interviews. Since 2005, participants are invited for follow-up visits during adulthood (including fasting blood samples). Approximately 1,400 children have been recruited into the study up to 2010. Recent findings revealed e.g. (i) the relevance of early life factors for subsequent development of body composition and puberty timing, (ii) the relation between pubertal hormonal status and puberty onset, (iii) age and time trends in iodine status and modern dietary habits and (iv) potential furan and benzol exposition by commercial weaning foods. Future analyses will provide insight into the extent to which health in young adulthood is receptive to diet, anthropometric pattern and hormonal status in distinct potentially critical periods during childhood.

Muscularity and adiposity in addition to net acid excretion as predictors of 24-h urinary pH in young adults and elderly.

OBJECTIVE: In patients with nephrolithiasis, an inverse relationship between 24-h urinary pH (24h-UpH) and body weight has been reported. Whether body composition indices and 24h-UpH are similarly associated in healthy subjects needs investigation. DESIGN: Cross-sectional, retrospective analysis. SETTING: Dortmund, Germany and Gothenburg, Sweden. SUBJECTS: Healthy young adults (18-23 years; n=117) and elderly (55-75 years; n=85) having a mean body mass index (BMI) of 22.80+/-3.4 and 25.3+/-3.9 kg/m2, respectively. METHODS: Anthropometric data, 24h-UpH, and 24-h urinary excretion rates of net acid (NAE), creatinine, and urea were determined. After adjusting for urea (reflecting protein intake), renal creatinine output was used as a biochemical marker for muscularity. The BMI served as a marker of adiposity. RESULTS: NAE, body weight, and BMI were significantly (P<0.05) higher, and height and creatinine significantly lower in the elderly, whereas body-surface area (BSA) was not different. Step-wise multiple regression analysis using BSA-corrected urinary variables revealed NAE as the primary predictor of 24h-UpH (with R2 values of 0.64 and 0.68 in young adults and elderly, respectively, P<0.0001), followed by urea (P<0.0001), creatinine (P<0.05), and BMI (P<0.05 for the young adults and P=0.12 for the elderly). These associations were negative for NAE and BMI, and positive for urea and creatinine. CONCLUSIONS: Muscularity (i.e. creatinine adjusted for urea) and particularly in the group of young adults, adiposity (i.e. BMI) proved to be modest, but significant predictors of 24h-UpH. Future research should focus on more obese subjects in whom insulin resistance and particular kidney functions should also be examined to further substantiate the role of obesity in low-urine pH-associated conditions, for example, nephrolithiasis.

(13)C mixed triglyceride breath testing using infrared spectrometry: comparison of two devices in early infancy.

BACKGROUND/OBJECTIVES: The (13)C mixed triglyceride (MTG) breath test has been proposed for the non-invasive assessment of fat digestion and absorption. To evaluate whether reference values for the adequacy of fat absorption, set in the non-dispersive infrared spectrometry (NDIRS) system software proposed for healthy children and adults using the (13)C MTG breath test, are also applicable to infants of <5 months of age. SUBJECTS/METHODS: (13)C MTG breath testing with the NDIRS technique was performed in 54 healthy infants <5 months of age (38 breast-fed, 16 formula-fed) and six infants diagnosed with cystic fibrosis (CF) using two NDIRS devices, IRIS and FANci2. RESULTS: The IRIS results were slightly higher compared with those assessed by the FANci2 device. The minimum cutoff value for pancreatic sufficiency (PS) is set as a cumulative percentage dose of (13)C recovered (cPDR) after 5 h of 13.0%. Pancreatic function status of six CF infants, three with PS and three with pancreatic insufficiency (PI), according to the 72 h-faecal fat balance test could be correctly determined with the (13)C MTG breath test using two NDIRS techniques. However, if these reference values had been used to determine pancreatic function status in healthy infants, 26 out of 54 infants would have been misclassified as pancreatic insufficient. CONCLUSIONS: Although the (13)C MTG breath test with the MS technique has the potential to be a suitable assessment of fat absorption in infants, the technique of NDIRS appears too insensitive in an infant population group.

Urinary 24-h creatinine excretion in adults and its use as a simple tool for the estimation of daily urinary analyte excretion from analyte/creatinine ratios in populations.

BACKGROUND/OBJECTIVES: The assessment of urinary excretion of specific nutrients (e.g. iodine, sodium) is frequently used to monitor a population's nutrient status. However, when only spot urines are available, always a risk of hydration-status-dependent dilution effects and related misinterpretations exists. The aim of the present study was to establish mean values of 24-h creatinine excretion widely applicable for an appropriate estimation of 24-h excretion rates of analytes from spot urines in adults. SUBJECTS/METHODS: Twenty-four-hour creatinine excretion from the formerly representative cross-sectional German VERA Study (n=1463, 20-79 years old) was analysed. Linear regression analysis was performed to identify the most important influencing factors of creatinine excretion. In a subsample of the German DONALD Study (n=176, 20-29 years old), the applicability of the 24-h creatinine excretion values of VERA for the estimation of 24-h sodium and iodine excretion from urinary concentration measurements was tested. RESULTS: In the VERA Study, mean 24-h creatinine excretion was 15.4 mmol per day in men and 11.1 mmol per day in women, significantly dependent on sex, age, body weight and body mass index. Based on the established 24-h creatinine excretion values, mean 24-h iodine and sodium excretions could be estimated from respective analyte/creatinine concentrations, with average deviations <10% compared with the actual 24-h means. CONCLUSIONS: The present mean values of 24-h creatinine excretion are suggested as a useful tool to derive realistic hydration-status-independent average 24-h excretion rates from urinary analyte/creatinine ratios. We propose to apply these creatinine reference means routinely in biomarker-based studies aiming at characterizing the nutrient or metabolite status of adult populations by simply measuring metabolite/creatinine ratios in spot urines.

Role of nutritional status in the regulation of adrenarche.

The factors regulating adrenarche are unknown. Recent in vitro studies have demonstrated that insulin and insulin-like growth factor I induce major adrenal steroidogenic enzyme genes and increase the production of adrenal androgens. Literature findings strongly suggest that changes in body mass index (BMI) reflect an integrated nonhormonal index of changes in serum levels and/or bioactivities of insulin and insulin-like growth factor I. We therefore longitudinally investigated individual changes in BMI and urinary 24-h excretion rates of dehydroepiandrosterone sulfate (DHEAS) in a prepuberty (PreC; n = 22, 11 boys and 11 girls) and a puberty (PubC; n = 20, 10 boys and 10 girls) cohort of healthy children. Twenty-four-hour urine samples were collected at yearly intervals during observation periods that lasted at least 4 yr (comprising > or = 5 consecutive 24-h urine collections). For 4-yr intervals highly significant tracking coefficients (P < 0.001) of 0.73 (PreC) and 0.93 (PubC) were observed for DHEAS, emphasizing the importance of individual (and genetic) influences on adrenal androgen excretion. In both cohorts almost 3-fold higher median increases in urinary DHEAS excretion rates (P < 0.05) were observed during the 1-yr period of the individually highest rises in BMI compared with the 1-yr period of significantly lower rises in BMI (P < 0.01) in the same children after the factor age was controlled for. However, no consistently significant associations were found between urinary DHEAS output and BMI from simple cross-sectional correlations at defined age points. These findings provide the first in vivo evidence that a change in the nutritional status, measurable in the form of delta-BMI (but not BMI alone), is an important physiological regulator of adrenarche regardless of individual adrenal androgen excretion level, age, and developmental stage.

The midgrowth spurt in healthy children is not caused by adrenarche.

A small transient increase in growth, the midgrowth spurt, has been observed in several growth studies in healthy children around the age of 7 yr. During this time adrenarche (the physiological increase in adrenal androgen secretion) also occurs. Although it is now well established that estrogen, not androgen, has a critical role in the male (and female) pubertal growth spurt, a direct effect of androgens on growth cannot be excluded. In accordance with published observations that growth is frequently accelerated in infants and young children with late-diagnosed 21-hydroxylase deficiency (before adequate androgen suppression), it has been speculated that the adrenarchal increase in adrenal androgen secretion in healthy children could be responsible for the midgrowth spurt. To test this hypothesis we studied long-term serial changes in urinary 24-h excretion rates of dehydroepiandrosterone sulfate and total 17-ketosteroid sulfates in a group of healthy children (n = 12) in which yearly auxological measurements allowed the identification of a midgrowth spurt. Annual measurements of standing height were performed over periods of 6-9 yr before the onset of puberty. All children collected five to seven serial 24-h urine samples (1-yr intervals) each at the time of anthropometric examination. The peak of the midgrowth spurt was found to occur at a mean age of 6.8 +/- 1.0 yr. The average height of the midgrowth peak, i.e. average maximum gain in height velocity, was 0.9 cm/yr. In a peak-centered examination of individual 24-h excretion rates of dehydroepiandrosterone sulfate and 17-ketosteroid sulfates, primarily weak 1-yr changes in adrenal androgens were observed until the peak was attained. Only after the peak did increments in urinary adrenal androgen output become more pronounced. ANOVA performed on the peak-centered dehydroepiandrosterone sulfate and 17-ketosteroid sulfate excretion rates revealed a highly significant overall increase in adrenal androgen secretion from 2 yr before to 2 yr after the midgrowth spurt. After multiple testing, however, significant increments, when compared with the respective preceding androgen excretion levels, were for the first time seen 1 yr after the midgrowth spurt (dehydroepiandrosterone sulfate) or 2 yr later (17-ketosteroid sulfates). In conclusion, our longitudinal analysis of prepubertal growth and urinary adrenal androgen excretion in healthy children disproves the speculation that the midgrowth spurt is primarily caused by the adrenarchal increase in adrenal androgen secretion. However, the present results do not rule out a growth-accelerating effect of clearly higher androgen levels, as in premature adrenarche.

Short-term impact of a lactovegetarian diet on adrenocortical activity and adrenal androgens.

The aim of this study was to determine whether definite diet changes affect adrenocortical activity and/or adrenal androgen metabolism. A controlled experimental diet study with four consecutive diet periods (repeated measure design) was carried out in six healthy adult volunteers. Four nearly isoenergetic diets, two normal (N) moderately protein-rich, one protein-rich (P), and one low protein lactovegetarian (L), were fed. At the end of each 5-day diet period a blood sample and two 24-h urine specimens were obtained from each subject. Plasma levels of dehydroepiandrosterone sulfate (DHEAS) were elevated with diet L (6.5 +/- 1.4 vs. 5.3 +/- 1.1 mumol/L; P < 0.05) compared to diet N, whereas other plasma hormones, including cortisol and insulin-like growth factor I did not vary markedly. A marked increase of 60% was seen in the urinary 24-h output of 3 alpha-androstanediol glucuronide with diet P. Urinary 24-h excretion rates for C peptide, free cortisol, DHEAS, and total 17-ketosteroid sulfates were clearly reduced with diet L compared to those with diet N or P. Our results show that a lactovegetarian diet can reduce adrenocortical activity (at least after a short term diet change). In addition, this vegetarian nutrition leads to a particular metabolic situation (elevated plasma DHEAS and reduced urinary DHEAS output) that usually is characteristic of fasting. Peripheral androgen metabolism as reflected by urinary 3 alpha-androstanediol glucuronide appears to be influenced only by high protein intake (diet P). Further research (controlled dietary long term investigation) is required 1) to validate whether the effects of diet on adrenocortical activity represent sustained endocrine changes and 2) to elucidate the underlying mechanism.

Urinary excretion of galactosyl-hydroxylysine is a marker of growth in children.

Galactosyl-hydroxylysine (Gal-Hyl) is the predominant product of the posttranslational glycosylation of skeletal collagen. Urinary Gal-Hyl excretion is regarded as a marker of bone resorption in adults, but little information is available on the validity of this parameter in pediatric age groups. Using 24-h urine samples from 88 healthy children and adolescents ages 4-18 yr, reference ranges were established for this age group, and values were compared with measurements in children with overt GH deficiency (n = 14) or Ullrich-Turner syndrome (n = 21). When expressed relative to body weight (Gal-Hyl/wt), urinary Gal-Hyl excretion was 3.2 to 4.7 times higher in subjects 4-16 yr of age than in adults. Highest values were observed in very young children and during the pubertal growth spurt. In the total population, urinary Gal-Hyl/wt was closely related to growth velocity (r = 0.72) and significantly correlated with the urinary excretion of both hydroxyproline (r = 0.74) and deoxypyridinoline (r = 0.88; P < 0.001 each). Urinary Gal-Hyl/wt was significantly lower in children with GH deficiency or Ullrich-Turner syndrome than in healthy children (P < 0.001 each). The urinary excretion of Gal-Hyl was significantly correlated with growth velocity in GH-deficient children (r = 0.69; P = 0.004) but not in patients with Ullrich-Turner syndrome. In the latter, the increase in urinary Gal-Hyl excretion after 3 months of treatment with recombinant human GH correlated significantly with the increase in growth velocity after 12 months of treatment (r = 0.76; P = 0.002). We conclude that the urinary excretion of Gal-Hyl is a valid and potentially useful index of skeletal growth in children.

Estimation of the renal net acid excretion by adults consuming diets containing variable amounts of protein.

The object of this study was to determine whether it is possible to reliably estimate the renal net acid excretion (NAE) produced by adults consuming different amounts of dietary protein. A physiologically based calculation model that corrects for intestinal absorption of minerals and sulfur-containing protein and assumes a rate of urinary excretion of organic acids proportional to body surface area was used to estimate NAE. Urinary excretion of different minerals and NAE was measured during the last 48 h of each of four separate 5-d diet periods in six healthy adults. On the basis of food tables, the four nearly isoenergetic diets (one lacto-vegetarian and one high- and two moderate-protein diets) were estimated to yield the following NAE values: 3.7, 117.5, 62.2, and 102.2 mEq/d, respectively. The analytically determined urinary NAE (24.1 +/- 10.7, 135.5 +/- 16.4, 69.7 +/- 21.4, and 112.6 +/- 10.9 mEq/d) corresponded reasonably well to these estimates, suggesting that the calculation model is appropriate to predict the renal NAE from nutrient intake and anthropometric data.

The bone mass concept: problems in short stature.

Bone densitometry is currently one of the mainstays in the evaluation of systemic bone diseases in adults and is also increasingly used to assess primary or secondary bone disorders in children and adolescents. The purpose of carrying out densitometric studies in such circumstances is to measure the densitometric indicators of bone stability. Following procedures which were established for diagnosing adult osteoporosis, a decrease in densitometric surrogates of bone stability is usually interpreted as indicating increased fracture risk. The most basic densitometric parameter is bone mineral content (BMC), which can be measured with most densitometric techniques. BMC is either defined as the mass of mineral contained in an entire bone or as the mass of mineral per unit bone length. While mineral mass can be expected to be a good surrogate for bone stability, BMC is obviously a size-dependent parameter, since small bones weigh less than big bones. This is a drawback in paediatric use, since many children and adolescents who are examined by densitometry suffer from chronic disorders and are small-for-age. Short children will have a lower BMC than their healthy age-matched peers, even if their (smaller) bones are otherwise completely normal.

A moderate increase in daily protein intake causing an enhanced endogenous insulin secretion does not alter circulating levels or urinary excretion of dehydroepiandrosterone sulfate.

To study the effect of a moderate increase in insulin secretion produced by an increased daily protein intake on dehydroepiandrosterone sulfate (DHEAS), a balanced randomized crossover trial consisting of three strictly controlled dietary regimens was performed in six healthy male volunteers. The basic diet (B) contained 50 g protein/d; diets P and M (also basic diets) were enriched with either 32 g protein/d (P) or 10 mmol L-methionine/d (M). Methionine was given (as a specific nonprotein source of endogenously derived sulfate) to control for possible confounding effects on DHEAS due to an increased sulfate supply. At the end of each 4-day diet period, blood and 24-hour urine samples were collected. Fasting plasma levels of testosterone, cortisol, insulin-like growth factor-I (IGF-I), and insulin, as well as urinary output of total (hot acid-cleaved) testosterone conjugates and 3alpha-androstanediol glucuronide, did not show significant changes in response to dietary manipulations. Endogenous sulfate availability (as reflected by renal sulfate output per 24 hours) approximately doubled with diets P and M. However, plasma levels (6.3 +/- 1.5, 6.8 +/- 1.8, and 6.9 +/- 2.1 micromol/L for B, P, and M, respectively) and urinary excretion (8.8 +/- 9.8, 9.4 +/- 11.2, 8.0 +/- 8.3 micromol/d) of DHEAS remained unaffected. Considering the clear increments (P < .01) in urinary C-peptide excretion with diet P (20.4 +/- 10.3 nmol/d) versus diets B and M (12.6 +/- 5.1 and 13.2 +/- 3.6 nmol/d), respectively, our results suggest that a moderately strong diet-induced increase in daily insulin secretion does not alter urinary and plasma levels of DHEAS.

Re-examination of the effect of hCG on plasma levels and renal excretion of dehydroepiandrosterone sulfate in healthy males.

To reinvestigate the effect of hCG on circulating and urinary dehydroepiandrosterone sulfate (DHEAS), a hCG stimulation test (5000 IU administered i.m. at 8.30 h on 3 consecutive days) was performed in 6 healthy males (aged 24 to 35 years). Blood specimens and 24-h urine samples were collected immediately before the first and directly after the last hCG administration. Contrary to previous findings in normal men, the present study revealed significant DHEAS responses after testicular stimulation with hCG: plasma DHEAS increased from 7.9 +/- 2.3 to 9.6 +/- 2.2 mumol/L (P < 0.05) and urinary DHEAS from 5.7 +/- 3.6 to 9.3 +/- 5.2 mumol/day (P < 0.05). There was also a marked rise (P < 0.05) in the urinary excretion of total 17-ketosteroid sulfates. Clear increases of unconjugated plasma dehydroepiandrosterone as well as of circulating and renally excreted androstenedione and testosterone definitely confirmed an adequate Leydig cell stimulation. Significant post-hCG changes were additionally observed for plasma and urinary 3 alpha-androstanediol glucuronide (149% and 79% increases, respectively) and for urinary cortisol (21% decrease). Significant correlations were found for the post-hCG percent increases of plasma androstenedione versus plasma DHEAS (r = 0.86) and for the percent increases of plasma testosterone versus urinary DHEAS (r = 0.98), indicating that the extent of gonadal androgen elevations in the circulation of normal men is a determinant of DHEAS increases in blood or urine. These findings provide an explanation for the frequently observed sex differences for DHEAS in adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of urinary androgen sulfates without previous hydrolysis: a tool to investigate adrenarche. Validation of a commercial radioimmunoassay for dehydroepiandrosterone sulfate.

A commercial 125I radioimmunoassay designed for the quantification of dehydroepiandrosterone sulfate (DHEAS) in blood samples was tested for its direct applicability to 24-hour urine samples from children and adults. Average recoveries in parallelism and spiking experiments were found to be near 100%. Intra- and inter-assay coefficients of variation were below 10%. Urinary DHEAS concentrations determined directly by the radioimmunoassay (x) differed only slightly from corresponding radioimmunoassay values (y) obtained after C18 reversed-phase extraction and LH-20 chromatography (y = 0.85x + 0.12; r = 0.99). Cross-reactivity data from related steroids suggested only a small contribution to the DHEAS titer by other steroids. In 8-year-old children compared to preadrenarchal children (4 years old) a clearly increased median daily urinary DHEAS output could be observed both for absolute excretion data (0.163 versus 0.05 mumol/d, P < 0.01) and for excretion values related to body surface area (0.181 versus 0.071 mumol/d/1.73 m2, P < 0.05). However, this "onset of adrenarche" was no longer statistically significant when urinary creatinine was taken as adjustment parameter for renal androgen sulfate output. After correction with the individual body surface area, rises of urinary DHEAS from childhood to adulthood were nearly in the order of the literature data on age-corresponding serum increases of DHEAS. In conclusion, the direct radioimmunological quantification of DHEAS in 24-hour urine samples with subsequent correction for individual body surface area appears to present a physiologically meaningful way to assess the adrenal gland's secretory activity for this androgen sulfate.

Measurement of urinary androgen sulfates without previous hydrolysis: a tool to investigate adrenarche. Determination of total 17-ketosteroid sulfates.

According to published data the group of urinary total 17-ketosteroid sulfates appears to represent an index of overall adrenal androgen production, at least before the onset of puberty. To quantify total 17-ketosteroid sulfates a modified colorimetric assay based on the Zimmermann reaction was validated. 17-ketosteroid sulfates were measured without previous hydrolysis (as conjugated Zimmermann chromogens against authentic dehydroepiandrosterone sulfate (DHEAS) as assay standard) after C18 reversed-phase extraction and LH-20 chromatography. Intra- and inter-assay coefficients of variation were 8.4% (15.0%) and 5.9% (17.6%), respectively, at urinary 17-ketosteroid sulfate concentrations of 10.8 (1.9) nmol/ml. Recoveries observed in spiking and parallelism experiments varied between 88 and 102%. In a group of 4-year-old children showing a renal DHEAS output of less than 0.1 mumol/d/1.73 m2 (measured by radioimmunoassay) a relatively high median 17-ketosteroid sulfate excretion of 1.29 mumol/d/1.73 m2 was found. Older children aged 8 years as well as a group aged 12-14 years demonstrated only moderately higher urinary 17-ketosteroid sulfates whereas excretion of DHEAS/d/1.73 m2 more than tripled from age group to age group. For children from 8 years onwards, adolescents, and adults, linear regression analysis indicated that urinary DHEAS elevations seem to contribute with a constant proportion of approximately 70% to the increments of total urinary 17-ketosteroid sulfates. These findings suggest that the attainment of such a constant relationship (between the total 17-ketosteroid sulfates and their major component) from about 8 years of age onwards could represent the hormonal correlate of the completion of the continuous zona reticularis in the adrenal gland (developing around this age from a focal reticularis zone).

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.

Adrenarche and nutritional status.

The prepubertal fat spurt seen in mid-childhood coincides with the beginning of adrenarche and is associated with rising serum levels of insulin and insulin-like growth factor-I. As the adrenal cortex expresses receptors for these anabolic peptides, implying that the nutritional status is communicated to the adrenal gland, we hypothesized that nutritional status may be causally involved in the regulation of adrenal androgen secretion. To test this hypothesis, anthropometric indices of the nutritional status and 24-h urinary excretion rates of dehydroepiandrosterone sulfate (DHEAS) were studied longitudinally (during observation periods of at least 4 years) in healthy normal-weight prepubertal and pubertal children. Increases in urinary DHEAS excretion proved to be significantly elevated during periods of individual highest rises in body mass index. These findings provide the first in vivo evidence that a change in nutritional status is an important physiological regulator of adrenarche.

Established dietary estimates of net acid production do not predict measured net acid excretion in patients with Type 2 diabetes on Paleolithic-Hunter-Gatherer-type diets.

BACKGROUND/OBJECTIVES: Formulas developed to estimate diet-dependent net acid excretion (NAE) generally agree with measured values for typical Western diets. Whether they can also appropriately predict NAE for 'Paleolithic-type' (Paleo) diets-which contain very high amounts of fruits and vegetables (F&V) and concurrent high amounts of protein is unknown. Here, we compare measured NAEs with established NAE estimates in subjects with Type 2 diabetes (T2D). SUBJECTS/METHODS: Thirteen subjects with well-controlled T2D were randomized to either a Paleo or American Diabetes Association (ADA) diet for 14 days. Twenty-four hour urine collections were performed at baseline and end of the diet period, and analyzed for titratable acid, bicarbonate and ammonium to calculate measured NAE. Three formulas for estimating NAE from dietary intake were used; two (NAE_diet R or L) that include dietary mineral intake and sulfate- and organic acid (OA) production, and one that is empirically derived (NAE_diet F) only considering potassium and protein intake. RESULTS: Measured NAE on the Paleo diet was significantly lower than on the ADA-diet (+31±22 vs 112±52 mEq/day, P=0.002). Although all formula estimates showed similar and reasonable correlations (r=0.52-0.76) with measured NAE, each one underestimated measured values. The formula with the best correlation did not contain an estimate of dietary OA production. CONCLUSIONS: Paleo-diets are lower in NAE than typical Western diets. However, commonly used formulas clearly underestimate NAE, especially for diets with very high F&V (as the Paleo diet), and in subjects with T2D. This may be due to an inappropriate estimation of proton loads stemming from OAs, underlining the necessity for improved measures of OA-related proton sources.

Prospective association of protein intake during puberty with body composition in young adulthood.

OBJECTIVE: To examine the association of habitual animal and plant protein intake during the potentially critical period of puberty with body composition in young adulthood. DESIGN AND METHODS: Multivariable regression analyses were performed on data from 140 female and 122 male participants of the DONALD Study with ≥2 3-day weighed dietary records during puberty (girls 9-14 years; boys 10-15 years) and anthropometric measurements in young adulthood (18-25 years). Fat-free mass index (FFMI) and fat mass index (FMI) were estimated from four skinfolds. RESULTS: In women, a higher pubertal animal protein consumption was independently related to higher levels of FFMI (ptrend = 0.001), but not to FMI (ptrend = 0.5). Adjusted means of FFMI in energy-adjusted tertiles of animal protein intake were 15.3 (95% confidence interval: 15.0, 15.5), 15.4 (15.1, 15.7), 16.2 (15.9, 16.6) kg/m(2) . In men, a higher animal protein intake was related to a higher FFMI (ptrend = 0.04) and a lower FMI (ptrend = 0.001) only after adjusting FFMI for current FMI levels and vice versa. Plant protein was not associated with body composition among either sex. CONCLUSIONS: Our results show that a higher pubertal animal protein consumption may yield a higher fat-free mass in young adulthood.