Validation testing demonstrates efficacy of a 7-day fluid record to estimate daily water intake in adult men and women when compared with total body water turnover measurement

Abstract

Background: Mean daily water intake from fluids (WATER-FL) has proven to be difficult to measure because of a range of nonvalidated data collection techniques. Few questionnaires have been validated to estimate WATER-FL against selfreported diaries or urinary hydration markers, which may limit their objectivity. Objectives: The goals of this investigation were 1) to assess the validity of a 7-d fluid record (7dFLR) tomeasureWATER-FL (WATER-FL-7dFLR) through comparison with WATER-FL as calculated by measuring deuterium oxide (D2O) disappearance (WATER-FL-D2O), and 2) to evaluate the reliability of the 7dFLR in measuring WATER-FL. Methods: Participants [n = 96; 51% female; mean ± SD age: 41 ± 14 y; mean ± SD body mass index (in kg/m2): 26.2 ± 5.1] completed body water turnover analysis over 3 consecutiveweeks. They completed the 7dFLR and food diaries duringweeks 2 and 4 of the observation. The records were entered into nutritional software to determine the water content of all foods and fluids consumed. WATER-FL-D2Owas calculated fromwater turnover (via the D2Odilution method),minus water from food and metabolic water. The agreement between the 2 methods of determining WATER-FL were compared according to a Bland- Altman plot at week 2. The test-retest reliability of 7dFLR between weeks 2 and 4 was assessed via intraclass correlation (ICC). Results: The mean ± SD difference between WATER-FL-7dFLR and WATER-FL-D2Owas 2131 ± 845 mL/d. In addition, no bias was observed (F[1,94]=0.484; R2=0.006; P = 0.488).When comparingWATER-FL-7dFLR fromweeks 2 and 4, no significant difference (mean6 SD difference: 716 75 mL/d; t[79] = 0.954; P = 0.343) and an ICC of 0.85 (95%CI: 0.77, 0.90) was observed. Conclusions: The main findings of this study were that the use of the 7dFLR is an effective and reliable method to estimate WATER-FL in adults. This style of questionnaire may be extremely helpful for collecting water intake data for large-scale epidemiologic studies.