We appreciate the letter from Hew-Butler and the EAH (Exercise-Associated Hyponatremia) Panel regarding our recent study on inadequate hydration among children in the United States. We agree with the author that our data do not support the conclusion that, “a majority of the world’s children are dehydrated.” We made no such claim. Instead, using the 800 milliosmoles per kilogram urine osmololality (Uosm) threshold for inadequate hydration from previous research,1 which Hew-Butler and the EAH Panel note is associated with thirst stimulation, we found that more than half (54.5%) of the children in the United States may be inadequately hydrated—or thirsty—at any given time. We specifically used the term “inadequate hydration” rather than “dehydration” because the threshold of 800 Uosm does not serve as a clinical indicator of urgent dehydration.
Despite the challenge of measuring hydration status in a population sample, which remains problematic even when using plasma indicators,2 we believe that our findings highlight an important public health problem that deserves additional research and action. Our goal was not to argue that more than half of US youths are seriously ill from clinical dehydration. Rather, we aimed to estimate the population prevalence of milder inadequate hydration given that this may be associated with deficits in well-being and cognition. We agree that further research on hydration and cognition in children using stronger study designs is warranted; however, there is a more robust body of literature demonstrating negative effects in adults.3
Hyponatremia is harmful to the small number of children who experience it.4 However, most US youths do not consume adequate water as defined by the Institute of Medicine,5,6 and many of the spaces where children learn and play have limited water access.7,8 We do not suggest that well-hydrated children should drink water to excess, but rather that we need to increase access to water and encourage healthy levels of consumption for the many US children who do not get enough of it.
References
- 1.Stookey JD, Brass B, Holliday A, Arieff A. What is the cell hydration status of healthy children in the USA? Preliminary data on urine osmolality and water intake. Public Health Nutr. 2012;15(11):2148–2156. doi: 10.1017/S1368980011003648. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Armstrong LE. Assessing hydration status: the elusive gold standard. J Am Coll Nutr. 2007;26(5 suppl):575S–584S. doi: 10.1080/07315724.2007.10719661. [DOI] [PubMed] [Google Scholar]
- 3.Masento NA, Golightly M, Field DT, Butler LT, van Reekum CM. Effects of hydration status on cognitive performance and mood. Br J Nutr. 2014;111(10):1841–1852. doi: 10.1017/S0007114513004455. [DOI] [PubMed] [Google Scholar]
- 4.Reid-Adam J. Hyponatremia. Pediatr Rev. 2013;34(9):417–419. doi: 10.1542/pir.34-9-417. [DOI] [PubMed] [Google Scholar]
- 5.Drewnowski A, Rehm CD, Constant F. Water and beverage consumption among children age 4-13y in the United States: analyses of 2005-2010 NHANES data. Nutr J. 2013;12:85. doi: 10.1186/1475-2891-12-85. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Kant AK, Graubard BI. Contributors of water intake in US children and adolescents: associations with dietary and meal characteristics–National Health and Nutrition Examination Survey 2005-2006. Am J Clin Nutr. 2010;92(4):887–896. doi: 10.3945/ajcn.2010.29708. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Kenney EL, Gortmaker SL, Carter JE, Howe MCW, Reiner JF, Cradock AL. Grab a cup, fill it up! An intervention to promote the convenience of drinking water and increase student water consumption during school lunch. Am J Public Health. 2015 doi: 10.2105/AJPH.2015.302645. Epub ahead of print. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Patel AI, Hampton KE. Encouraging consumption of water in school and child care settings: access, challenges, and strategies for improvement. Am J Public Health. 2011;101(8):1370–1379. doi: 10.2105/AJPH.2011.300142. [DOI] [PMC free article] [PubMed] [Google Scholar]