title: Ultra-long-term human salt balance studies reveal interrelations between sodium, potassium, and chloride intake and excretion.
abstract: The intake of sodium, chloride, and potassium is considered important to healthy nutrition and cardiovascular disease risk. Estimating the intake of these electrolytes is difficult and usually predicated on urine collections, commonly for 24 h, which are considered the gold standard. We reported on data earlier for sodium but not for potassium or chloride.
  
  
  
  We were able to test the value of 24-h urine collections in a unique, ultra-long-term balance study conducted during a simulated trip to Mars.
  
  
  
  Four healthy men were observed while ingesting 12 g salt/d, 9 g salt/d, and 6 g salt/d, while their potassium intake was maintained at 4 g/d for 105 d. Six healthy men were studied while ingesting 12 g salt/d, 9 g salt/d, and 6 g salt/d, with a re-exposure of 12 g/d, while their potassium intake was maintained at 4 g/d for 205 d. Food intake and other constituents were recorded every day for each subject. All urine output was collected daily.
  
  
  
  Long-term urine recovery rates for all 3 electrolytes were very high. Rather than the expected constant daily excretion related to daily intake, we observed remarkable daily variation in excretion, with a 7-d infradian rhythm at a relatively constant intake. We monitored 24-h aldosterone excretion in these studies and found that aldosterone appeared to be the regulator for all 3 electrolytes. We report Bland-Altman analyses on the value of urine collections to estimate intake.
  
  
  
  A single 24-h urine collection cannot predict sodium, potassium, or chloride intake; thus, multiple collections are necessary. This information is important when assessing electrolyte intake in individuals.
authors.affiliation: Interdisciplinary Center for Clinical Research, Nikolaus Fiebiger Center for Molecular Medicine, and.
authors.forename: Anna
authors.initials: A
authors.lastname: Birukov
authors.affiliation: Experimental and Clinical Research Center, an institutional cooperation between the Charité Medical Faculty and the Max Delbrück Center, Berlin, Germany;
authors.forename: Natalia
authors.initials: N
authors.lastname: Rakova
authors.affiliation: Interdisciplinary Center for Clinical Research, Nikolaus Fiebiger Center for Molecular Medicine, and.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Lerchl
authors.affiliation: Department of Internal Medicine, Division of Nephrology, University of Amsterdam, Academic Medical Center, Amsterdam, Netherlands;
authors.forename: Rik Hg
authors.initials: RH
authors.lastname: Olde Engberink
authors.affiliation: Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany;
authors.forename: Bernd
authors.initials: B
authors.lastname: Johannes
authors.affiliation: Fresenius Medical Care, Bad Homburg, Germany; and.
authors.forename: Peter
authors.initials: P
authors.lastname: Wabel
authors.affiliation: Fresenius Medical Care, Bad Homburg, Germany; and.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Moissl
authors.affiliation: Department of Pediatrics, Faculty of Medicine, Friedrich Alexander University, Erlangen-Nuremberg, Germany;
authors.forename: Manfred
authors.initials: M
authors.lastname: Rauh
authors.affiliation: Experimental and Clinical Research Center, an institutional cooperation between the Charité Medical Faculty and the Max Delbrück Center, Berlin, Germany; Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN friedrich.luft@charite.de.
authors.forename: Friedrich C
authors.initials: FC
authors.lastname: Luft
authors.affiliation: Interdisciplinary Center for Clinical Research, Nikolaus Fiebiger Center for Molecular Medicine, and Division of Clinical Pharmacology, Vanderbilt University School of Medicine, Nashville, TN.
authors.forename: Jens
authors.initials: J
authors.lastname: Titze
mesh_terms: D000328:Adult; D000450:Aldosterone / Q000652:urine; D004032:Diet; D004573:Electrolytes / Q000008:administration & dosage / Q000652:urine*; D006801:Humans; D000071217:Infradian Rhythm; D008137:Longitudinal Studies; D008297:Male; D011188:Potassium / Q000008:administration & dosage / Q000652:urine*; D012964:Sodium / Q000008:administration & dosage / Q000652:urine*; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000652:urine*; D014882:Water-Electrolyte Balance
chemical_list: D004573:Electrolytes; D017673:Sodium Chloride, Dietary; D000450:Aldosterone; D012964:Sodium; D011188:Potassium
keywords: aldosterone; chloride; diet; electrolyte intake; potassium; salt; sodium; urine