Total water intake by kilogram of body weight: Analysis of the Australian 2011 to 2013 National Nutrition and Physical Activity Survey.

Abstract

Water is critical for human survival, yet water intake equations may not reflect contemporary populations. This research aims to determine the total water intake of a representative Australian population, per kilogram of body weight (mL/kg) and stratified by age and sex. A secondary analysis of the 2011 to 2013 National Nutrition and Physical Activity Survey (n=10 146) was conducted. Dietary intake from food and beverages was assessed by a 24-hour recall, with respondent's weight objectively measured. Data were descriptively analysed, with multiple linear regressions used to identify the impact of demographic and physiologic factors on total water intake (mL/kg). The median (interquartile range) daily total water intake per kilogram of body weight for children (2-8 years), adolescents (9-18 years) and adults (19+ years) were 77.1 (57.4-100)mL/kg, 40.4 (29.3-53.4)mL/kg and 35.5mL/kg (26.1-47.8), respectively. Increasing height and waist circumference were associated with reduced total water intake, with a change of -1.03 mL/kg (-1.43, -0.618) [coefficient (95% confidence interval)] in children for height and -0.448 mL/kg (-0.484, -0.412) in adults for waist circumference. Similarly, seasonality decreased intake, with greatest reductions in winter [adolescents: -4.11 mL/kg (-6.83, -1.40)]. In comparison, being male, living in rural areas and having a physical occupation were associated with greater intake, by 1.73 mL/kg (0.347, 3.10), 4.74 mL/kg (3.47, 6.00) and 2.82 (trade workers: 1.08, 4.59) in adults, respectively. Total water intake (mL/kg) decreased with age in both sexes. The results highlight possibilities to incorporate other factors into water intake equations to improve their accuracy.