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Schoolchildren Should Drink More Water

November 21, 2013 by Michael Greger M.D. in News with 14 Comments

Does a Drink of Water Make Kids Smarter?

Most children arrive at school in a state of mild dehydration that may negatively affect scholastic performance.

Preventing cellular dehydration is integral to hormonal, immune, neurological, cardiovascular, gastrointestinal, muscle and skeletal function. So researchers recently set out to determine the hydration status of healthy children in the United States. Urine samples were obtained from groups of 9 to 11 year olds in Los Angeles and Manhattan on their way to school to see how they were doing.

The study was motivated by recent studies in Israel showing children did not seem to be hydrated enough. But Israel’s in a desert, so they wanted to repeat the study under cooler and less arid conditions. It turns out the U.S. kids did just as bad as the Israelis.

As I show in my video Does a Drink Of Water Make Children Smarter?, urine from nearly two-thirds of the U.S. kids studied was considered too concentrated, an indicator that they were dehydrated. Why? They weren’t drinking enough water. Three-quarters of the kids did not drink water between the time they woke up and when they went off to school.

But most ate breakfast, so they must have been drinking something. The problem is that other beverages are not as hydrating. The levels of sodium, sugars, and amino acids in milk and juice can shrink cells and trigger the release of the hormone that spurs dehydration.

So what, though? Is there any actual negative impact of mild dehydration on one’s ability to function at school? Historically, most of the studies on hydration and mental functioning were done on adults under extreme conditions, like having people exercise in 113 degree heat, or giving people powerful diuretics like Lasix and putting them on a treadmill. Most of the studies on hydration and cognitive performance have been performed on military personnel to evaluate soldiers’ ability to function in extreme circumstances. It is easy to imagine that a soldier fighting in the desert with a heavy rucksack and a protective suit must be physically and cognitively at his best. It is, however, very difficult to translate this knowledge to normal real-life circumstances. Three new studies changed that.

They were simple studies. Researchers took a group of schoolchildren, randomly allocated them to drink a cup of water or not, and then gave them all a test to see who did better. And the winner was… the cup-of-water group. Conclusion: “The results of the present study suggest that even children in a state of mild dehydration, not induced by intentional water deprivation or by heat stress and living in a cold climate, can benefit from drinking more water and improve their cognitive performance.”

So water worked for 2nd and 3rd graders, what about 1st grade? Same experimental design but this time instead of forcing kids in the water group to drink a cup, the water group was just given some water and told to drink as much they wanted, and again found significant improvement in the performance of various tasks, leading to the same conclusion: “[E]ven under conditions of mild dehydration…children’s cognitive performance can be improved by having a drink of water.”

The latest study that just came out is the largest to date.  It too found a remarkable proportion of children were in a state of mild, voluntary dehydration at the beginning of the school day and a significant negative correlation between dehydration and, for example, the ability to remember numbers. The researchers offered a randomized group some water, and those kids on average felt better and performed better. “To conclude…[mild dehydration] is an adverse state that might render the school day more challenging for children.”

Even doctors often apparently fail to realize the connection. A recent survey found that healthcare professionals under-recognized the importance of proper hydration for mental health. Who would care enough about the importance of human hydration to even do a survey? A “Hydration Institute” founded in part by…The Coca-Cola company.

These three new studies found drinking resulted in a significant improvement in cognitive performance, but not with Coke. And not with Ritalin or some new drug, either. Just plain water. Think how much drug companies could make if they could sell sugar pills but just tell kids to take the fake pill with… a glass of water.

This is one of those groundbreaking findings (like my gargling video) that will likely never see the light of day because there’s no profit motive for promotion. We’re guaranteed to be assailed about all the new drugs and surgical advances because there’s big business behind getting the word out. But who profits from tap water? Or even broccoli for that matter? That’s one of the reasons I created NutritionFacts.org, to bring to light all the findings that would otherwise just get buried in medical library basements (or, increasingly, vast private databases).

The water content of plant foods may help explain why those eating plant-based diets are, on average, so slim. Like fiber, water is a source of Nutrition Without Calories. See Dietary Guidelines: It’s All Greek to the USDA for a country with the guts to suggest water might be preferable to drinking soda.

Juice and milk may not be as hydrating as water. What about tea? See my video Is Caffeinated Tea Dehydrating? What about Bottled Water vs. Tap?

More on children’s health in videos such as:

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2014 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, and From Table to Able.

Image credit: JefferyTurner / Flickr

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Dr. Michael Greger

About Michael Greger M.D.

Michael Greger, M.D., is a physician, author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial. Currently Dr. Greger proudly serves as the Director of Public Health and Animal Agriculture at the Humane Society of the United States.

View all videos by Michael Greger M.D.

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  • Catherine J Frompovich

    Encouraging children to drink more water is admirable, however, industrial-waste-produced fluoride added to municipal water systems is not conducive to health of teeth [dental fluorosis http://en.wikipedia.org/wiki/Dental_fluorosis ], body, and brain. Developmental fluoride toxicity was addressed in a Harvard University meta study http://www.ncbi.nlm.nih.gov/pubmed/22820538

    that concluded, in part, “Thus, children in high-fluoride areas had significantly lower IQ scores than those who lived in low-fluoride areas.”

    Furthermore, “Fluorides are general protoplasmic poisons.”
    http://www.fluoridation.com/quotes.htm
    These are scientific facts that are ignored and ought to be addressed if we want our children to be healthy. It would seem that municipal water fluoridation is a failed ‘public health policy’ that needs to be revisited and removed from practice.

    • Leslie

      We are all “eating” fluoridated” water, especially vegans (that’s the bulk of what we eat. So many of our plants/crops are grown with fluoridated water (irrigation). The huge salad I’m having right now, the apples later, the raspberries tonight, etc.
      I doubt that all farms are running off a well, that many of them are tapped into the municipal water system. I heard a theory once that if you eat an abundance and variety of greens and fruit, you are ingesting way more fluoride than you would had you been drinking fluoridated tap water. I hope it is not correct but this makes me pause to consider….the logic is there.

      • Alex

        Do keep in mind, if you’re eating a whole-foods, plant-based diet focusing on high-nutrient fruits and veggies, you’re body can handle a few molecules of fluoride and pesticide residues. It’s rather frustrating that people worry so much about the crap in water and on vegetables, and instead would rather go eat an “organic, grass-fed” steak that probably has way more chemicals than those released from my car in a day. Focus on the big picture, not the reductionist chemical.

        • Leslie

          Actually, feel my concern is valid as well as part of the big picture – 100 percent of my diet comes from plants, and a whole lot of those plants are irrigated – I have been led to believe – with fluoridated water. I think long-term this does not bode well for the soil, nor for human health. It is my hope that the day will come when farms are required to install water filtration systems. If I thought that the big picture was just “don’t eat meat and don’t drink milk ” I’d be eating mass handfuls of potato chips and other junk of the kind. But no thanks on the chips. Thanks for the reply.

          • Alex

            Oh, no, I was more so talking to Catherine. Sorry for the misconception. But, yes, I agree, that’s why I emphasized WHOLE food, plant based, b/c that excludes potato chips.

    • Toxins
  • HemoDynamic, M.D.

    I love todays blog for many reasons but I love it the most that you said this:
    “This is one of those groundbreaking findings (like my gargling video) that will likely never see the light of day because there’s no profit motive for promotion. We’re guaranteed to be assailed about all the new drugs and surgical advances because there’s big business behind getting the word out. But who profits from tap water? Or even broccoli for that matter? That’s one of the reasons I created NutritionFacts.org, to bring to light all the findings that would otherwise just get buried in medical library basements (or, increasingly, vast private databases).”

    Reminds me of a wonderful quote by Gandhi:
    “When I despair, I remember that all through history the way of truth and love have always won. There have been tyrants and murderers, and for a time, they can seem invincible, but in the end, they always fall. Think of it–always.”
    ― Mahatma Gandhi

    Keep up the great work!!!

    • DH

      HemoDynamic, while I like the quote from Gandhi, I think he is incorrect. Look around at the modern dictatorships and failed states that currently abound in the world – from Zimbabwe to modern-day Russia. “The way of truth and love has always won.” Sure, Hitler and Stalin are dead but for the latter (Stalin) was not because truth and love won, but because he had a hemorrhagic stroke! The fall of communism was replaced by the rise of kleptocracy and mafia-style Putinism. When I look at the world today, I see more suffering than ever before (and I don’t even own a TV). Dr Greger shines a light on an important part of the world and provides goodness in that way, but overall, the world is a wretched place and always has been.

  • Ariel Gail MacLean

    I am so glad you have focused on this extremely important overlooked health issue with kids; in my case, the pattern of dehydration as a baseline default state was established early and unknowingly continued into and throughout my adult life. It has taken me a half century to connect this issue which contributes to and manifests as numerous health issues across multiple systems. One problem not addressed here is the fact that public drinking fountains (the only feasible solution for kids already shackled with heavy backpacks) are notoriously contaminated in a variety of ways ranging from mouths on the spigot to the leaching of corrosive or chemically imbedded pipes. Because of this, I taught my children to never use public fountains unless it was an emergency. Wouldn’t this be a great use of our federal health resources and infrastructure, to get a clean drinking water delivery system up and running at every school, which children lined up to partake in as they walked in the door.

  • Em Crone

    I am so glad that I never have a problem drinking water. I drink waaaaayyyy more than other people.

  • Noor Pekala

    We should all drink more water, as my grandma said Water is the drink of the gods, that’s why people don’t drink it (enough).

    The fluoride is a scary thing though: my mom was prescribed a fluoride mouth wash by a dentist, that made her so ill! Fluoride attacks 2 disparate things – hips and ears / hearing. She’d broken a hip even though as a health nut, veg*n for 60 some years her calcium levels were fine, and no one in her family had hearing problems, but the fluoride very suddenly left her almost deaf! No idea what was making her ill, but a dr. in Sweden (she was there on vacation) told her she was poisoned by way too much fluoride. How could a fertilizer by-product like fluoride be good?!? Well the fertilizer folks are snake-oil sales people! They needed to get rid of it, so why dump it if you can SELL it? Even if it keeps cavities at bay, why cut off your nose to spite your face? Just cut back on that other poison, sugar! Even though we Americans think we’re all that, Europe is way ahead of us in the fluoride dept. it’s outlawed there!!

  • Sebastian Tristan

    Question on absorption of nutrients: You very interestingly mention that for the nutrients from vegetables to be well absorbed, one must eat the vegetables with some oil. Is this valid also for fruits and legumes?

  • http://www.johnarrowoodonline.com/ John Arrowood

    Thanks doctor. Could you expkain how amino acids and sodium can cause dehydration in someone who has normally functioning kidneys? As a RD I’m concerned some may misinterpret and pass up nutrient dense (vitamin D and calcium) milk for water.

    • http://www.DonForresterMD.com/ Don Forrester MD

      Amino acids that are not used by the body are eliminated via the liver and kidney. Any solutes going out of the kidney bring water with them contributing to relative dehydration. However our kidneys are “smart” and are designed to help maintain a proper level of hydration. It is when our body is subjected to foods that we were not designed to eat that things get thrown out of balance. Since we are designed as hind-gut fermenting herbivores any processed foods including oils and animal foods especially dairy (i.e. designed for calfs) that we eat are more difficult for our body to handle than a whole plant food based diet. Sodium doesn’t necessary contribute to dehydration but excess leads the body to retain fluid. I disagree that milk is nutrient dense. There are much better ways to get Vit D and calcium than dairy. I would recommend you watch some of the 106 videos on dairy and there attached abstracts/full articles under each video. Another good resource is the book, Whitewash, by Joseph Keon which is thorough and has cited references.

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