Abstract
PurposeMild-to-moderate iodine deficiency was present in large parts of Germany up to the beginning 1990s and improved from then on. Current epidemiological data on spot urine iodine measurements in German children strongly suggest the re-occurrence of an impaired iodine status. We thus examined whether this re-occurrence is identifiable in more detail, through iodine analyses of 24-h urine samples of a well-characterized cohort of German children in whom samples have been systematically collected from 1985 onward. As iodized salt is a major source for iodine supply, urinary sodium excretion was additionally studied.MethodsDaily iodine and sodium excretions were measured in 2600 24-h urine samples collected between 1985 and 2018 by 677 healthy children aged 6–12 years (participants of the DONALD study). These data were compared with 24-h iodine and sodium excretion estimates obtained from spot urine samples collected in the representative German Health Interview and Examination Surveys for Children and Adolescents KiGGS-baseline (2003–2006) and KiGGS-wave-2 (2014–2017).ResultsBetween 1985 and1992, DONALD participants started with a median daily iodine excretion level of 40.1 µg/d. Then, during 1993–2003, iodine excretions mounted up to an approximate plateau (~ 84.8 µg/d). This plateau lasted until 2012. Thereafter, iodine concentrations started to decrease again resulting in a median iodine excretion of only 58.9 µg/d in 2018. Sodium excretion, however, had increased. The marked decrease in iodine status along with an abundant sodium excretion corresponded closely with nationwide KiGGS data.ConclusionsAs exemplified for the clearly worsening iodine status in German children, longitudinal cohort studies collecting detailed biomarker-based prospective data have the potential to reliably capture health-relevant nutritional changes and trends, applicable on a more comprehensive and even representative population level.
Highlights
Germany is an iodine-deficient region [1] and goiter prevalence was above 10% up to the beginning 1990s in several German regions [2]
As along with milk and milk products, iodized salt, contained in processed foods, is the most important source for iodine supply in Germany [7, 8], we studied whether some kind of long-term reduction in salt intake—assessed via 24-h urinary sodium excretion measurements—might have contributed to the recent impairment in iodine status
Representative spot urine measurements as well as specific cohort data on 24-h urine collections hint at a situation in Germany where about 50% (6–8 years old) or 45% (9–12 years old) of school children were at risk of iodine deficiency, i.e., their estimated iodine intakes are below the estimated average requirements (EAR) (Fig. 3C)
Summary
Germany is an iodine-deficient region [1] and goiter prevalence was above 10% up to the beginning 1990s in several German regions [2]. Several years later the Robert Koch-Institute accomplished a nationwide representative survey in German children during the years 2003–2006 (KiGGS baseline) followed by a second one KIGGS wave 2 (KiGGS-2) around 11 years later (2014–2017). These surveys, done with spot urine collections, revealed a further improvement in iodine. As along with milk and milk products, iodized salt, contained in processed foods, is the most important source for iodine supply in Germany [7, 8], we studied whether some kind of long-term reduction in salt intake—assessed via 24-h urinary sodium excretion measurements—might have contributed to the recent impairment in iodine status
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