Just Sip It: More Than Half Of U.S. Kids Not Properly Hydrated

One statistic jumped out at me from this study by researchers at the Harvard School of Public Health about whether U.S. kids are drinking enough water: "Nearly a quarter of the children and adolescents in the study reported drinking no plain water at all."

When you think about the kinds of serious health problems your kids might have, not drinking quite enough water may not top your list.

But it's serious: beyond the physical problems related to insufficient water-drinking, there are cognitive implications as well, researchers report:

Inadequate hydration has implications for children’s health and school performance. Drinking water can improve children’s performance on cognitive tests. Two studies have found that children’s cognitive performance improved as their urine osmolality [a measure of urine concentration] decreased. Increasing drinking water access in schools may be a key strategy for reducing inadequate hydration and improving student health, because schools reach so many children and adolescents and that they typically provide free drinking water to students.

The study was published online in the American Journal of Public Health.

I asked Erica Kenney, a postdoctoral researcher and one of the study authors, a few questions about the work. Here, lightly edited, is what she said, via email.

RZ: What's the takeaway here?

EK: We often take for granted that kids will keep themselves hydrated automatically and will drink when they're thirsty, or that their schools, summer camps, afterschool programs, child care centers, etc. will be providing them with enough opportunities to drink water during the day. But our study indicates that this may not be the case — over half of all children and adolescents in the U.S. are estimated to be inadequately hydrated. We need to do a better job of getting safe, clean, appealing drinking water to kids (and by "we" I don't just mean parents and families — I also mean the places where kids learn and play during the day) and keeping them hydrated so that they have the opportunity to be at their best in terms of well-being, cognitive functioning, and mood.

Where do we go from here?

I know researchers always like to say, "More research!" But I think it's true in this case — this was a sort of preliminary study to try to understand the scope of this potential public health issue, and it's really just describing the issue nationally — it's not getting at the "why" or the "how do we fix it." We need more evidence on what can be effective strategies to improve and change hydration status in kids, and also more research on what some of the barriers might be for kids to drink water and even other fluids during the school day. Is it that they are reluctant to ask for the hall pass to go to the bathroom so they opt not to drink anything? Or that there isn't much water available where they are? Several school districts are starting to explore innovative strategies for getting more water to kids during the school day (New York City recently tried putting chilled water dispensers and cups right on their lunch line and found it increased student water intake; there was a pilot intervention in LA a few years ago to distribute reusable water bottles to students), and I think this is an important step forward.

What were the kids actually drinking if not water?

We actually didn't look in the study at what a kid was drinking if they didn't drink water. Water was the most commonly consumed beverage, followed by SSBs, milk, juice, diet beverages, and coffee and tea (the last three were pretty infrequently consumed). The issue was more that there was still a pretty large number of kids who didn't drink any water, and that even if they were drinking some water (or other beverages), they appear to have not been drinking enough to stay adequately hydrated. This matches some findings from another researcher who looked at the other side of this equation by calculating how much water kids were intaking and comparing to the Institute of Medicine's recommendations for adequate water intake (and here, by "adequate water intake," this means total fluid intake — so total water from all beverages and foods), and found that kids were not consuming enough total water either.

The NPR story on the study notes that the researchers did not start out looking into water consumption per se:

The Harvard scientists who turned up the finding were initially looking into the consumption of sugary drinks in schools and looking for ways to steer children toward water instead — a much healthier beverage.

Along the way, they noticed that "kids weren't really drinking that much fluid," says postdoctoral researcher Erica Kenney at Harvard's T.H. Chan School of Public Health. She wondered if that was posing any problems for them.

So she and her colleagues dug into data from the National Health and Nutrition Examination Survey, which gathers an amazing amount of information from study participants, including chemical tests of their urine. Those urine tests reveal whether people are adequately hydrated — people who don't take in enough water have darker, saltier urine.

From the Harvard news release:

More than half of all children and adolescents in the U.S. are not getting enough hydration--probably because they're not drinking enough water--a situation that could have significant repercussions for their physical health and their cognitive and emotional functioning, according to the first national study of its kind from Harvard T.H. Chan School of Public Health.

The study also found racial/ethnic and gender gaps in hydration status. Black children and adolescents were at higher risk of inadequate hydration than whites; boys were at higher risk than girls...

"These findings are significant because they highlight a potential health issue that has not been given a whole lot of attention in the past," said lead author Erica Kenney, a postdoctoral research fellow in the Department of Social and Behavioral Sciences at Harvard Chan School. "Even though for most of these kids this is not an immediate, dramatic health threat, this is an issue that could really be reducing quality of life and well-being for many, many children and youth."

Drinking enough water is essential for physiological processes such as circulation, metabolism, temperature regulation, and waste removal. Although excessive dehydration is associated with serious health problems, even mild dehydration can cause issues, including headaches, irritability, poorer physical performance, and reduced cognitive functioning.

The researchers looked at data from 2009-2012 on more than 4,000 children and adolescents aged 6 to 19 years who participated in the National Health and Nutrition Examination Survey, a study of the health of U.S. children and adults conducted each year by the Centers for Disease Control and Prevention. They used urine osmolality--a measure of how concentrated a person's urine is--to determine whether or not participants were adequately hydrated.

They found that a little more than half of all children and adolescents weren't getting enough hydration. Boys were 76% more likely than girls, and non-Hispanic blacks were 34% more likely than non-Hispanic whites, to be inadequately hydrated.

Notably, nearly a quarter of the children and adolescents in the study reported drinking no plain water at all.

"The good news is that this is a public health problem with a simple solution," said senior author Steven Gortmaker, professor of the practice of health sociology. "If we can focus on helping children drink more water--a low-cost, no-calorie beverage--we can improve their hydration status, which may allow many children to feel better throughout the day and do better in school."

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Rachel Zimmerman Reporter
Rachel Zimmerman previously reported on health and the intersection of health and business for WBUR. She is working on a memoir about rebuilding her family after her husband’s suicide. 



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