title: The influence of season and air temperature on water intake by food groups in a sample of free-living Japanese adults.
abstract: OBJECTIVE
  To examine the influence of season and climate (air temperature and humidity) on water intake by the food group in a sample of free-living Japanese adults.
  
  
  METHODS
  Four-nonconsecutive-day, semi-weighed dietary records were collected from each of the four seasons in a single 12-month period (16 days in total). The influence of season and climate on individual water intake by the food group was analyzed using a mixed linear model. Participants were 242 healthy adults (121 women aged 30-69 years and 121 men aged 30-76 years) from four areas in Japan.
  
  
  RESULTS
  For women and men together, the mean total water intake was 2230 g/day (highest in summer: 2331 g/day; lowest in winter: 2134 g/day). Fifty-one percent of water was derived from foods and the rest from beverages. In a mixed linear model adjusted for sex, age and body mass index, intake of water from foods decreased by 3.1 g/day and that from beverages increased by 8.4 g/day, with an increase in the mean outdoor air temperature on the survey day of 1 °C (both P < 0.0001). The influence of humidity was nonsignificant.
  
  
  CONCLUSIONS
  In contrast to previous findings in Western countries, half of water intake in Japanese adults was derived from foods. Water intake from beverages was positively associated with air temperature, whereas that from foods was inversely associated with air temperature.
authors.affiliation: Department of Social and Preventive Epidemiology, School of Public Health, the University of Tokyo, Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tani
authors.affiliation: 1] Department of Social and Preventive Epidemiology, School of Public Health, the University of Tokyo, Tokyo, Japan [2] Interfaculty Initiative in Information Studies, Graduate School of Interdisciplinary Information Studies, The University of Tokyo, Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Asakura
authors.affiliation: Department of Social and Preventive Epidemiology, School of Public Health, the University of Tokyo, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
authors.affiliation: Graduate School of Health Science, Matsumoto University, Matsumoto, Nagano, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Hirota
authors.affiliation: Department of Food Science and Nutrition, Tottori College, Tottori, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Notsu
authors.affiliation: Department of Public Health and Hygiene, School of Medicine, University of the Ryukyus, Nakagami-gun, Okinawa, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Todoriki
authors.affiliation: Department of Health and Nutritional Sciences, Faculty of Health Promotional Sciences, Tokoha University, Hamamatsu, Shizuoka, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Miura
authors.affiliation: Department of Statistics, Osaka City University Medical School, Osaka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Fukui
authors.affiliation: Department of Food Science and Nutrition, School of Human Science and Environment, University of Hyogo, Himeji, Hyogo, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Date
mesh_terms: D000328:Adult; D000368:Aged; D001628:Beverages / Q000032:analysis*; D015930:Diet Records; D004034:Diet Surveys / Q000379:methods; D004326:Drinking; D004327:Drinking Behavior; D005260:Female; D005504:Food Analysis; D064368:Healthy Volunteers; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D012111:Residence Characteristics; D012621:Seasons; D013696:Temperature