Contribution of fruit and vegetable intake to hydration status in schoolchildren

The specific effects of fruit and vegetable (F&V) intake on water balance and consequently on 24-h hydration status (HS) are unknown.

In a large observational cohort of German children, we examined whether a higher F&V intake per se is associated with improved HS and attempted to quantify the influence of greater consumption of F&Vs on HS.

A total of 1286 complete 3-d weighed dietary records and 24-h urine samples for 442 children (4- to 10-y-olds) collected in 2000-2010 in the Dortmund Nutritional and Anthropometric Longitudinally Designed Study were analyzed. Free water reserve [FWR; urine volume (mL/24 h) minus obligatory urine volume (mL/24 h)] served as an HS biomarker. Median FWR and water balance variables were analyzed in different categories of solid-F&V intakes. Repeated-measures regression models (PROC MIXED; SAS Institute), adjusted for all other dietary water sources, were used to quantify the separate effects of solid-F&V and F&V-juice consumption on FWR.

Negative FWR values, which indicated risk of hypohydration, were observed in 22% of children. FWR was significantly higher in solid-F&V consumers with high intakes than in those with low intakes (P < 0.0001). PROC MIXED models predicted an increase of 46 mL in FWR (average in boys and girls) when increasing solid-F&V intake by 100 g. Similar results were observed for F&V juice (β = 43, P < 0.0001). Drinking water and milk were the other significant dietary predictors of FWR. Solid F&Vs and F&V juices contributed 12% and 10%, respectively, to total water intake.

These data confirm that regular intake of F&Vs may relevantly improve HS in children. Dietary interventions to increase F&V intake may be a promising strategy to achieve positive water balance in this population.