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Item Type: | Article |
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Title: | Increased salt consumption induces body water conservation and decreases fluid intake |
Creators Name: | Rakova, N., Kitada, K., Lerchl, K., Dahlmann, A., Birukov, A., Daub, S., Kopp, C., Pedchenko, T., Zhang, Y., Beck, L., Johannes, B., Marton, A., Müller, D.N., Rauh, M., Luft, F.C. and Titze, J. |
Abstract: | BACKGROUND: The idea that increasing salt intake increases drinking and urine volume is widely accepted. We tested the hypothesis that an increase in salt intake of 6 g/d would change fluid balance in men living under ultra-long-term controlled conditions. METHODS: Over the course of 2 separate space flight simulation studies of 105 and 205 days' duration, we exposed 10 healthy men to 3 salt intake levels (12, 9, or 6 g/d). All other nutrients were maintained constant. We studied the effect of salt-driven changes in mineralocorticoid and glucocorticoid urinary excretion on day-to-day osmolyte and water balance. RESULTS:A 6-g/d increase in salt intake increased urine osmolyte excretion, but reduced free-water clearance, indicating endogenous free water accrual by urine concentration. The resulting endogenous water surplus reduced fluid intake at the 12-g/d salt intake level. Across all 3 levels of salt intake, half-weekly and weekly rhythmical mineralocorticoid release promoted free water reabsorption via the renal concentration mechanism. Mineralocorticoid-coupled increases in free water reabsorption were counterbalanced by rhythmical glucocorticoid release, with excretion of endogenous osmolyte and water surplus by relative urine dilution. A 6-g/d increase in salt intake decreased the level of rhythmical mineralocorticoid release and elevated rhythmical glucocorticoid release. The projected effect of salt-driven hormone rhythm modulation corresponded well with the measured decrease in water intake and an increase in urine volume with surplus osmolyte excretion. CONCLUSION: Humans regulate osmolyte and water balance by rhythmical mineralocorticoid and glucocorticoid release, endogenous accrual of surplus body water, and precise surplus excretion. FUNDING: Federal Ministry for Economics and Technology/DLR; the Interdisciplinary Centre for Clinical Research; the NIH; the American Heart Association (AHA); the Renal Research Institute; and the TOYOBO Biotechnology Foundation. Food products were donated by APETITO, Coppenrath und Wiese, ENERVIT, HIPP, Katadyn, Kellogg, Molda, and Unilever. |
Keywords: | Dietary Sodium Chloride, Glucocorticoids, Mineralocorticoids, Space Flight, Water, Water-Electrolyte Balance |
Source: | Journal of Clinical Investigation |
ISSN: | 0021-9738 |
Publisher: | American Society for Clinical Investigation |
Volume: | 127 |
Number: | 5 |
Page Range: | 1932-1943 |
Date: | 1 May 2017 |
Additional Information: | Copyright © 2017, American Society for Clinical Investigation |
Official Publication: | https://doi.org/10.1172/JCI88530 |
External Fulltext: | View full text on PubMed Central |
PubMed: | View item in PubMed |
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