Pop quiz: How much water should we drink each day?
You already know the answer, right? Eight glasses, I hear you say. Eight eight-ounce glasses, in fact, I hear you say.
I know. We all know. It’s been drilled into our heads since… since… since time immemorial, right?
So much so that a couple years ago I bought this mug you see to the right. This really big mug. The idea was to find a mug for use at work that would hold my daily water requirement – that magic 64 ounces that we all need. And I even found one at my local Super-Mega-Hyper-Mart™ that fit the bill perfectly. Trust me, this sucker is big. I’ll admit, it’s hard to appreciate the mug’s presence and stature without reference objects, but if I had put anything too close to it, said object would be irretrievably trapped in the mug’s gravity well.
But that’s not all — not only is GargantuMug big, it’s informative, too. It mentions the 64-ounce guideline, tells you what things could go wrong with you if you get dehydrated, tells you to drink this much in a day, and even gets silly now and then. In upside down text, it reads, “If you can read this, I need more water!”
So clever! So useful! And yet…
Maybe not so useful…
An article in Scientific American from last June sheds some light on the story. Physician Heinz Valtin, MD, from Dartmouth Medical School, found no evidence of any science indicating a reason to drink that much water, and also saw no evidence in the general population of their being chronically dehydrated to the point of needing to drink 3½ gallons of water each week. He did locate what is believed to be the origin of the “8×8 rule”, and it’s interesting, to say the least (emphasis mine):
Valtin thinks the notion may have started when the Food and Nutrition Board of the National Research Council recommended approximately “1 milliliter of water for each calorie of food,” which would amount to roughly two to two-and-a-half quarts per day (60 to 80 ounces). Although in its next sentence, the Board stated “most of this quantity is contained in prepared foods,” that last sentence may have been missed, so that the recommendation was erroneously interpreted as how much water one should drink each day.
To quote Mr. Spock.. “fascinating”. A misinterpretation of a recommendation back in 1945 has resulted in the commonly-held belief that we all need roughly a six-pack of water every day.
It goes even further. Of course, we also all know that the 64 ounces have to be actual water, right? That soft drinks — especially caffeinated soft drinks — don’t count, right?
Finally, strong evidence now indicates that not all of the prescribed fluid need be in the form of water. Careful peer-reviewed experiments have shown that caffeinated drinks should indeed count toward the daily fluid intake in the vast majority of persons. To a lesser extent, the same probably can be said for dilute alcoholic beverages, such as beer, if taken in moderation.
And really, when it comes down to it, the whole “caffeinated drink doesn’t count because it’s a diuretic” idea doesn’t really pass the sniff test. Think about it. The idea was that the diuretic effect of the caffeine it made the drink not count. Would a 12-ounce can of caffeinated Coke really make you urinate an extra 12 ounces? That seems unlikely (Of course, that’s easy to say now, given that I’ve just quoted the results of experiments backing up that point).
Basically, I see two takeaways from this.
One is about the water – if you’re thirsty, drink something. If you’re not, don’t. If you like water, drink it. If you’d rather drink something else, that’s good too. Just stop stressing about it!
And the other has to do with science in general. I’ve had people say that science is too rigid, and once its mind is made up (science has a mind?), it doesn’t change. But honestly, nothing could be farther from the truth. When supplied with evidence, science changes, and that’s an important point to teach our children. T-Rex models look different now. Pluto is no longer a planet. There’s water on the moon. The coelacanth is not extinct. There’s life on Earth in ridiculously hostile environments. And most people don’t need to drink 64 ounces of water every day.
When science is viewed as a process, not a book of facts, it becomes alive and exciting. Let your kids in on the amazing way our knowledge changes thanks to science.
..Rob T. is going to scratch all the incorrect information off of his GargantuMug – and then only drink about 3 ounces out of it!