One of the most recurring health wisdoms is that you need to drink 8 glasses of water daily.
Also known as the 8×8 (8 glasses of 8 ounces each) or 2 Litres of water daily.
I seems to make sense to so many people, including bottled water sellers, that for many people it is pure common sense.
From my medical training I already liked to tell people who tried to convince me to have my 8 daily glasses, the stories of people who died from “water intoxication” including a spate of deaths in my own state from people trying to avoid the dehydration when they took the party drug, Ecstasy.
On a more personal level, this idea of 8 daily glasses of water ended for me when I watched the “Lawrence of Arabia” movie and watched an Englishman train himself to drink water like a desert-living Arab.
Of course this was a movie, not science.
But often movies are better than science for personal change anyway.
Still the idea of 8 glasses of water on a daily basis has been put to the test by researchers, and in summary – the idea doesn’t hold water.
The most complete study was this year in the Journal of the American Society of Nephrology.
The best thing about this study was that they specifically addressed the 4 key health benefits proposed for 8 glasses of water daily: that it leads to more toxin excretion, improves skin tone, makes one less hungry and reduces headache frequency.
All these had no scientific evidence of benefit, and the closest was the question of affecting appetite where two studies disagreed with each other, and the researchers considered it was worth looking into further.
Of course this all begs one question.
Where did this daily water myth come from?
An excellent review paper in 2002 in the American Journal of Physiology suggested a possible source. Professor Valtin proposed that…
…the notion may have started when the [US] 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 (64 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.
Myth busted. There is no scientific basis for a recommendation of 8 glasses of water a day.
So what’s my advice?
I say decide for yourself.
[What do you expect on a self help blog, really.]
More specifically, figure out how to know when you are thirsty. The signals for wanting water in are as clear-cut as the ones for wanting water out. We just seem to get better trained on the full bladder than we do on the parched lips.
Then have what ever you feel like; water, other fluids (even caffeinated ones), or foods that have water in them.
If adding a bit more water than that helps you with headaches, skin tone, appetite etc go for it.If it doesn’t then don’t.
-Dr Martin Russell