Johnson, Evan C.

The reference values for daily total water intake from fluids and foods (TWI) from the Institute of Medicine (IOM) are 2.7 and 3.7 liters for females and males, respectively. Recent studies suggest that for optimal water intake 24h urine osmolality should be maintained below 500 mmol·kg −1 . Purpose To determine the total water intake requirement for healthy adults to maintain 24h urine osmolality below 500 mmol·kg −1 . Methods Urinary concentration was assessed in 48 men and 50 women (age: 41±14 y, body mass index: 26.2±5.1 kg·m −2 ) via urine osmolality from 24h samples (UOsm). TWI was assessed via water turnover using the deuterium dilution (D 2 O) method throughout a 7‐day time period, corrected for metabolic water production. The diagnostic accuracy of TWI to identify UOsm ≤ 500 mmol·kg −1 was evaluated using receiver operating characteristic (ROC) analysis in men and women separately. Results UOsm was 511±232 and 402±203 mmol·kg −1 and TWI was 3.54±1.08 L·d −1 and 3.20±1.27 L·d −1 in men and women, respectively. 32% of men and 55% of women met IOM guidelines for TWI. ROC analysis for TWI detecting UOsm ≤ 500 mmol·kg −1 in men yielded an area under the curve (AUC) of 77.4% with sensitivity, specificity, and threshold values of 83.3%, 64.5%, and 3.39 L·d −1 , respectively. In women, the AUC was 82.4% with sensitivity, specificity, and threshold values of 85.7%, 72.1%, and 2.61 L·d −1 , respectively. Conclusion Considering threshold values in men and women of 3.39 L·d −1 and 2.61 L·d −1 , respectively, maintaining TWI in line with IOM guidelines of 3.7 L·d −1 in men and 2.7 L·d −1 in women should be sufficient for most individuals to maintain 24h urine osmolality less than 500 mmol·kg −1 . Support or Funding Information This research was supported by Danone Research. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .