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

Khan NA, Westfall DR, Jones AR, Sinn MA, Bottin JH, Perrier ET, Hillman CH (2019) J Nutr. 2019 Sep 2. pii: nxz206. doi: 10.1093/jn/nxz206. [Epub ahead of print]

Web URL: Read this and related abstracts on PubMed here

Abstract:

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 ≤ 0.01). Similarly, osmolality [low (mean ± SD): 912 ± 199 mOsmol/kg, AL: 790 ± 257.0 mOsmol/kg, high: 260 ± 115 mOsmol/kg] and USG [low (mean ± SD): 1.023 ± 0.005, AL: 1.020 ± 0.007, high: 1.005 ± 0.004] during the low intervention were greater during AL, and both were greater than during the high intervention (all P ≤ 0.01). USG and osmolality AL values were related to switch task measures (β: 0.21 to -0.31, P < 0.05). Benefits of the high intervention were observed during the switch task, whereby participants exhibited 34% lower working memory cost relative to the low intervention. No significant changes in cognition were observed for the flanker and go/no-go tasks.

CONCLUSIONS:

The water intervention improved urinary markers of hydration and had selective benefits during task switching. Furthermore, children's cognitive flexibility selectively benefits from greater habitual hydration and water intake.