Over the years, all of us have heard how important it is to have kids drink water at school. That reminds me of a true story…
On one of my trips out to a school district, I was picked up at the airport by the local superintendent. We struck up a conversation on the way to the event. Since my topic was brain-related, the superintendent was gushing about how his district was now “brain compatible.”
I said, “Really? That’s great. Tell me what you’re doing.”
With a good deal of pride, he said, “We have water bottles on every kid’s desk.”
At that point I politely replied, “That’s nice.”
But IS it “nice”?
Is water on the desks really a good idea?
Years ago, I often repeated things I had heard from others who I thought were experts. But many were self-proclaimed experts who were also repeating what they had heard from other experts. Put enough experts together in one room and you have… grander delusions. Bottom line is that I was, at times, too careless and failed to go dig for the quality research. I know better now. Today, lean in close and read the truth about drinking water.
First, many of the studies promoted as “evidence” to support more hydration have 100 or fewer in the study. That’s too risky to draw much of a conclusion from, and has too few participants to generalize. In our first study, 58 children aged 7-9 years old were randomly allocated to either a group that received additional water or to a group that did not. Results showed that children who drank additional water rated themselves as significantly less thirsty than the control group and they performed better on visual attention tasks. Huh? What about every other type of task? That’s the best we can do? (Edmonds, et al. 2009)
Many questions arise from these studies.
For example, were the following variables teased out about the study:
What was the weather like during the study? How much humidity? Temperature?
What had the participants eaten? High or low water content foods?
Did the participants have any strenuous physical activity prior to the study?
What about water quality? Cultural favorite drinks? How about peer pressure?
Another study (same author) studied younger kids. This study had just 23 kids, aged 6-7 years old. There were improvements with the water group, who had less thirst and more “happiness.” They were also better on visual attention and visual search skills, but not visual memory or visuomotor performance (Edmonds, et al. 2009.) Again, too small of a sample, and the results are hardly dramatic.
Another recent study of 24 volunteers found that with a 24-hour dehydration, cognitive-motor function is preserved, but mood and reaction time deteriorated. No big shock there. There was a 2.6% decrease of body weight (woo-hoo!) during water deprivation (Szinnai, et al. 2005.) The most interesting part of this study was that females showed greater diminished capacity than males. In a follow-up study (Szinnai, et al. 2007) moderate dehydration induced by water restriction had no effect on blood pressure or heart rate reactivity to mental stress. However, stress-induced states become fortified during dehydration in females, but not males.
I was unable to find, anywhere in the medical journals, any scientific evidence that says, “Drink eight glasses of water per day.” In fact, getting too much water may be just as bad as not enough (Valtin, 2002.) In one study, when initial thirst was high, the more water ingested, the higher the performance. When initial thirst was low, the more water ingested, the poorer the performance. This reminds us NOT to go overboard with pushing water on students every ten minute. A drink of water can improve or impair mental performance depending on small differences in thirst. But make the water available, don’t push it on them.
There are, however, two additional issues to consider. One, children from lower income families cannot afford a constant supply of quality bottled water from home. It’s expensive and it’s no better than most tap water. Because of this, I suggest schools ensure all drinking fountains work well and have good water.
But wait; there’s more…
What about the studies on… Read more