Mild dehydration, defined as a 1-2 % loss in body mass caused by fluid deficit, is associated with risks of functional impairments and chronic diseases. Whether water requirements change with increasing age remains unclear. Therefore, the aim of the present investigation is to quantify hydration status and its complex determining factors from young to old adulthood to analyse age-related alterations and to provide a reliable database for the derivation of dietary recommendations. Urine samples collected over a 24 h period and dietary records from 1528 German adults (18 -88 years; sub-sample of the first National Food Consumption Survey) were used to calculate water intake (beverages, food and metabolic water) and water excretion parameters (non-renal water losses (NRWL), urine volume, obligatory urine volume) and to estimate hydration status (free-water-reserve) and 'adequate intake (AI)'. Median total water intake (2483 and 2054 ml/d, for men and women, respectively (P,0·0001)), decreased with increasing age only in males (P¼0·001). Obligatory urine volume increased in both sexes (P,0·0001) due to decreased renal concentration capacity. The latter was balanced by a decrease of NRWL (P,0·05), leaving the free-water-reserve and therefore hydration status almost unchanged. Calculated 'AI' of total water was the same for young (18 -24 years) and elderly ($65 years) adults (2910 and 2265 ml/d, for men and women, respectively). The present study is the first population-based examination showing that total water requirements do not change with age although ageing affects several parameters of water metabolism. Reduced sweat loss with increasing age appears to be primarily responsible for this observation.
Our findings in children and adolescents clearly show a better comparability of real 24h-UIE with est24h-UIEcrea than with UIC. Whenever highest possible validity is required for iodine status assessment from spot urine sampling, the determination of est24h-UIEcrea appears to be the more accurate monitoring approach.
Worldwide, the iodisation of salt has clearly improved iodine status. In industrialised countries, iodised salt added to processed food contributes most to iodine supply. Median urinary iodine concentration fell below the WHO criteria for iodine sufficiency of 100 mg/l in 2007 -9. Salt, milk, fish and egg intake (g/d) were significant predictors of UIE (P,0·005); and the main sources of iodine were salt and milk (48 and 38 %, respectively). The present data hint at a beginning deterioration in the iodine status of German schoolchildren. A decreased use of iodised salt in industrially produced foods may be one possible reason for this development. Because of the generally known risks for cognitive impairment due to even mild iodine deficits in children, a more widespread use of iodised salt, especially in industrially processed foods, has to be promoted.
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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.