title: Thermoregulatory responses are attenuated after fructose but not glucose intake.
abstract: OBJECTIVE
  We examined whether plasma hyperosmolality induced by oral monosaccharide intake attenuated thermoregulatory responses and whether the responses were different between fructose and glucose.
  
  
  METHODS
  Ten healthy young subjects performed three trials in a sitting position in an artificial climate chamber (ambient temperature, 28°C; relative humidity, 40%). After resting for 10 min, the subjects drank 300 mL of water alone (control), or 300 mL of water supplemented with 75 g fructose or 75 g glucose. Twenty minutes later, they were heated passively by immersing the lower legs in water at 42°C for 60 min. Plasma osmolality (Posm), sodium ([Na+]p) and insulin concentrations ([Ins]p), and percent change in plasma volume (%ΔPV) were measured, and esophageal temperature (Tes) thresholds for cutaneous vasodilation (THCVC) and sweating (THSR) at the forearm were determined.
  
  
  RESULTS
  Posm was significantly increased by fructose and glucose intake compared with water alone, although %ΔPV and [Na+]p were not significantly different among the three trials. [Ins]p was significantly higher after glucose intake than after fructose or water alone. THCVC and THSR were significantly higher after fructose intake than after glucose intake, which showed similar values to water intake.
  
  
  CONCLUSIONS
  These results suggest that the Tes threshold for thermoregulation is elevated after fructose intake, indicating the attenuation of thermoregulatory responses, whereas it is not attenuated after glucose intake. These results provide a novel insight to better determine the carbohydrate component of oral rehydration fluids for preventing dehydration and/or heat disorders.
authors.affiliation: 1Department of Environmental Physiology for Exercise, Osaka City University Graduate School of Medicine, Osaka, JAPAN; and 2Research Center for Urban Health and Sports, Osaka City University, Osaka, JAPAN.
authors.forename: Akina
authors.initials: A
authors.lastname: Suzuki
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Okazaki
authors.forename: Daiki
authors.initials: D
authors.lastname: Imai
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Takeda
authors.forename: Nooshin
authors.initials: N
authors.lastname: Naghavi
authors.forename: Hisayo
authors.initials: H
authors.lastname: Yokoyama
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Miyagawa
mesh_terms: D000328:Adult; D001628:Beverages; D001833:Body Temperature Regulation / Q000502:physiology*; D004947:Esophagus / Q000502:physiology; D005260:Female; D005440:Fluid Therapy; D005542:Forearm; D005632:Fructose / Q000008:administration & dosage*; D005947:Glucose / Q000008:administration & dosage*; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D009994:Osmolar Concentration; D010953:Plasma Volume / Q000502:physiology; D012867:Skin / Q000098:blood supply; D012964:Sodium / Q000097:blood; D013546:Sweating / Q000502:physiology; D013549:Sweetening Agents / Q000008:administration & dosage*; D014664:Vasodilation / Q000502:physiology; D055815:Young Adult
chemical_list: D007328:Insulin; D013549:Sweetening Agents; D005632:Fructose; D012964:Sodium; D005947:Glucose