Introduction and objective:
Hydration status is mainly influenced by the amount of beverages and water-rich foods they consume, although it is interesting to look for relations with other factors. Therefore, the aim of the study was to search for associations between hydration status and frequency of consumption of selected products, anthropometric measurements, and body composition in schoolchildren.

Material and methods:
A cross-sectional study was conducted in Polish primary schools, during d 2,849 schoolchildren aged 10–12 years examine. Food frequency questionnaires were used to assess the consumption of selected beverages and foods (FFQ). Anthropometric measurements were taken: height (H), body weight (BW), and waist circumference (WC). Body composition parameters: fat mass (FM), fat-free mass (FFM), and total body water (TBW) were measured using a bioelectrical impedance analysis (BIA). Hydration status was assessed by TBW measurement. Odds Ratios (OR) and 95% Confidence Intervals (95%) were calculated.

Results:
Variables that reduced the probability of dehydration were increased frequency of juice and vegetable consumption, and a high level of physical activity in study children. Additionally, a 1-unit increase in BMI was associated with increased odds of dehydration, and a 1-unit increase in FFM was associated with decreased odds.

Conclusions:
Consumption of beverages, especially water and products rich in this ingredient, should be promoted to ensure adequate hydration in children at home, as well as at school where children spend a large part of the day. This situation can be influenced by guaranteeing constant access to water by providing appropriate school infrastructure, such as water dispensers and springs, as well as workshops and educational activities.