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

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.

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.

Urinary fructose: a potential biomarker for dietary fructose intake in children.

BACKGROUND/OBJECTIVES: Recently, urinary fructose and sucrose excretion in 24-h urine have been established experimentally as new biomarkers for dietary sugar intake in adults. Our objective was to investigate 1) whether the fructose biomarker is also applicable in free-living children and 2) for what kind of sugar it is standing for. SUBJECTS/METHODS: Intakes of added and total sugar (including additional sugar from fruit and fruit juices) were assessed by 3-day weighed dietary records in 114 healthy prepubertal children; corresponding 24-h urinary fructose excretion was measured photometrically. The associations between dietary sugar intakes and urinary fructose excretion were examined using linear regression models. To determine whether one of the two sugar variables may be better associated with the urinary biomarker, the statistical Pitman's test was used. RESULTS: Added and total sugar correlated significantly with urinary fructose, but the linear regression indicated a weak association between intake of added sugar and urinary log-fructose excretion (ß=0.0026, R(2)=0.055, P=0.01). The association between total sugar intake and log-urinary fructose (ß=0.0040, R(2)=0.181, P<0.001) showed a significantly better fit (P<0.05). CONCLUSIONS: Urinary fructose excretion seems to be rather applicable for the estimation of total sugar intake than for the estimation of added dietary sugar intake in children. However, as excreted fructose stems almost exclusively from the diet (both from food-intrinsic and added intakes), it can be assumed that urinary fructose represents a potential biomarker for total dietary fructose intake, irrespective of its source.

[Iodine deficiency in infancy - a risk for cognitive development]. / Jodmangel im Säuglingsalter - ein Risiko für die kognitive Entwicklung.

Severe iodine deficiency during pregnancy seriously influences fetal brain development and in the worst case induces cretinism. Recent studies have shown that even a mild iodine deficiency during pregnancy and during the first years of life adversely affects brain development. The World Health Organisation (WHO) considers iodine deficiency as the most common preventable cause of early childhood mental deficiency. In this context, the insufficient production of the four iodine atoms containing thyroxine seems to play a causal role, i. e., due to the iodine substrate deficiency the neuronally particularly relevant free-thyroxine level falls. Due to the very limited iodine storage capacity, the infantile thyroid is eminently dependent on an adequate and steady iodine supply. In the first month of life, when milk is the only energy- and nutrient provider, infants fed a commercial formula regularly have a sufficient iodine supply. However, breastfed infants, who depend on maternal iodine status, frequently show an inadequate iodine intake. Furthermore, iodine intake is critical when complementary food (CF) is introduced. Especially homemade CF is poor in iodine, but also commercial CFs are only partly fortified. A simultaneous inadequate iodine supply of the breastfeeding mother and the preferential use of mostly iodine-poor organic milk cannot ensure an adequate iodine supply of the infant. In terms of an improvement of nutrient supply, especially concerning an unhindered brain development, the corresponding German reference value for iodine intake of infants until age 4 month should be raised from currently 40 microg/d to at least 60 microg/d (WHO-reference: 90 microg/d).