title: An empirical method to determine inadequacy of dietary water.
abstract: OBJECTIVE
  The physiological regulation of total body water and fluid concentrations is complex and dynamic. The human daily water requirement varies because of differences in body size, dietary solute load, exercise, and activities. Although chronically concentrated urine increases the risk of renal diseases, an empirical method to determine inadequate daily water consumption has not been described for any demographic group; instead, statistical analyses are applied to estimate nutritional guidelines (i.e., adequate intake). This investigation describes a novel empirical method to determine the 24-h total fluid intake (TFI; TFI = water + beverages + moisture in food) and 24-h urine volume, which correspond to inadequate 24-h water intake (defined as urine osmolality of 800 mOsm/kg; U800).
  
  
  METHODS
  Healthy young women (mean ± standard deviation; age, 20 ± 2 y, mass, 60.8 ± 11.7 kg; n = 28) were observed for 7 consecutive days. A 24-h urine sample was analyzed for volume and osmolality. Diet records were analyzed to determine 24-h TFI.
  
  
  RESULTS
  For these 28 healthy young women, the U800 corresponded to a TFI ≥2.4 L/d (≥39 mL/kg/d) and a urine volume ≥1.3 L/d.
  
  
  CONCLUSIONS
  The U800 method could be employed to empirically determine 24-h TFI and 24-h urine volumes that correspond to inadequate water intake in diverse demographic groups, residents of specific geographic regions, and individuals who consume specialized diets or experience large daily water turnover. Because laboratory expertise and instrumentation are required, this technique provides greatest value in research and clinical settings.
authors.affiliation: University of Connecticut, Department of Kinesiology, Human Performance Laboratory, Storrs, Connecticut, USA; University of Connecticut, Department of Nutritional Sciences, Storrs, Connecticut, USA. Electronic address: lawrence.armstrong@uconn.edu.
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Armstrong
authors.affiliation: University of Connecticut, Department of Kinesiology, Human Performance Laboratory, Storrs, Connecticut, USA.
authors.forename: Evan C
authors.initials: EC
authors.lastname: Johnson
authors.affiliation: University of Connecticut, Department of Kinesiology, Human Performance Laboratory, Storrs, Connecticut, USA.
authors.forename: Amy L
authors.initials: AL
authors.lastname: McKenzie
authors.affiliation: University of Connecticut, Department of Kinesiology, Human Performance Laboratory, Storrs, Connecticut, USA.
authors.forename: Colleen X
authors.initials: CX
authors.lastname: Muñoz
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000652:urine; D001834:Body Water / Q000502:physiology*; D003681:Dehydration / Q000652:urine*; D004032:Diet; D015930:Diet Records; D004326:Drinking; D005247:Feeding Behavior; D005260:Female; D005502:Food; D006801:Humans; D009994:Osmolar Concentration; D012016:Reference Values; D014867:Water; D014882:Water-Electrolyte Balance; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014867:Water
keywords: Fluid intake; Hydration assessment; Renal; Urine osmolality; Urine volume