In 2005, US water intake recommendations were based on analyses of Nutrition Healthand Examination Surveys (NHANES) III data that examined if hydration classification varied bywater intake and estimated the median water intake associated with hydration in persons aged 19⁻30. Given the upcoming 2020⁻2025 Dietary Guidelines review, this analysis addresses the same twoaims with the 2009⁻2012 NHANES data. Methods were updated by defining hydration criteria interms of multiple measures (serum sodium 135⁻144 mmol/L and urine osmolality < 500 mmol/kg),expressing water intake as ml/kg, distinguishing plain water intake (PWI) from total water intake(TWI), using weighted age- and sex-specific multivariable models to control for determinants ofwater intake requirements, and selecting two study samples (non-acutely ill US population and asub-group without selected chronic disease risk factors). In the US population and sub-group, therelative risk (RR) of meeting the hydration criteria was significantly greater for individuals withTWI ≥ 45 mL/kg or PWI ≥ 20 mL/kg (for the US population 19⁻50 years of age: adjusted RR (RRrepresents Relative Risk, which is a very standard term that probably does not need to be spelledout) = 1.36, 95% CI: 1.10⁻1.68 for males; adjusted RR = 1.70, 95% CI: 1.49⁻1.95 for females. For thesub-group 51⁻70 years of age: adjusted RR = 2.20, 95% CI: 1.15⁻4.18 for males; adjusted RR = 2.00,95% CI: 1.18⁻3.40 for females). The median (SE, which stands for Standard Error, which is also verywell known. Up to you if your journal prefers to spell it out in the abstract) TWI and PWI associatedwith meeting the hydration criteria for males and females 19⁻50 years of age were 42 (2) mL/kg and14 (1) mL/kg and 43 (2) mL/kg and 16 (1) mL/kg, respectively. The significant association betweenwater intake and hydration classification differs from the null association, underlying the 2005 waterintake recommendations, and may lead to different reasoning and inferences for the 2020⁻2025Dietary Guidelines.
Keywords: drinking water; hydration; serum sodium; total water intake; urine osmolality.