A 4-d Water Intake Intervention Increases Hydration and Cognitive Flexibility among Preadolescent Children

BACKGROUND: Hydration effects on cognition remain understudied in children. This is concerning since a large proportion of US children exhibit insufficient hydration. OBJECTIVE: This study investigated the effects of water intake on urinary markers of hydration and cognition among preadolescents. METHODS: A 3-intervention crossover design was used among 9- to 11-y-olds [n = 75 (43 males, 32 females); 58.2 +/- 28.5 BMI percentile]. Participants maintained their water intake [ad libitum (AL)] or consumed high (2.5 L/d) or low (0.5 L/d) water for 4 d. The primary outcomes were performance on cognitive tasks requiring inhibition, working memory, and cognitive flexibility assessed using a modified flanker, go/no-go, and color-shape switch tasks, respectively. Secondary outcomes included urine hydration indices [i.e., color, urine specific gravity (USG), osmolality] assessed using 24-h urine collected during day 4 of each intervention. Repeated-measures ANOVAs were used to assess intervention effects. RESULTS: There was a significant difference in hydration across all 3 interventions. Urine color during the low intervention [median (IQR): 6 (2)] was greater than during AL [5 (2)], and both were greater than during the high intervention [18 (0)] (all P