Busting The Myth of “Eight Glasses Of Water A Day”

Everyone knows we must drink 8 glasses of water a day, or else we’re going to get a failing grade at being a healthy human—like not flossing, or not using adequate sunscreen.

But… Do we? And does tea count? How about (we dare but whisper it) coffee? And soda drinks are mostly water, right? But aren’t some drinks dehydrating? Are special electrolyte drinks really better? There are so many things to consider, so many differing advices, and it’s easy to give up, or just choose what to believe in as a leap of faith.

A quick brain-teaser for you first, though:

If coffee and soda don’t count because they’re dehydrating, then what if you were to take:

– A concentrated tiny cup of espresso, and then a glass of water, would the glass of water count?

– Or (we don’t relish the thought) what if you took a spoonful of soda syrup, and then a glass of water, would the glass of water count?

If your answer was “yes, it’s a glass of water”, then why would it not count if it were taken all at once (e.g. as an Americano coffee, or a regular soda)?

If your answer was “yes, but that water might only offset the dehydration caused by the coffee/syrup, so I might only be breaking even”, then you were thinking about this the right way:

How much water you need depends on many factors that can be affected by what else you are consuming and what else you are doing. Science loves averages, so eight glasses a day may be great if you are of average health, and average body size, in a temperate climate, doing moderate exercise, and so on and so on.

If you’re not the most average person of all time? You may need to take into account a lot of factors, ranging from what you ate for dinner to how much you perspired during your morning exercises. As you (probably) don’t live in laboratory conditions, this can become an impossible task—and if you missed (or guessed incorrectly) even one factor, the whole calculation will be thrown off. But is there any other way to know?

What of the infamous pee test? Drink enough to make your urine as clear as possible, and if it’s dark, you’re dehydrated, common wisdom says.

In reality, however, that tells you not what’s in your body, but rather, what got ejected from your body. If your urine is dark, it might mean you had too little water, but it also could just mean you had the right amount of water but too much sodium, for instance. A study of this was done on athletes, and found no correlation between urine color and actual bodily hydration when measured directly via a blood test.

So, if we can’t just have an app tell us “drink this many glasses of water”, and we can’t trust urine color, what can we do?

What we can do is trust that our body comes with (for free!) a wonderful homeostatic system and it will try to correct any imbalances. If you are thirsty, you’re dehydrated. Drink something with plenty of water in, if not plain water.

But what about special electrolyte drinks? If you need salts, you will crave them. Craving a salty snack? Go for it! Or if you prefer not to snack, do a salt lick test (just put a little salt on your finger, and taste it; if it tastes good, wait a minute or two, and then have a little more, and repeat until it doesn’t).

Bonus Tip:

1. Make sure you always have a source of hydration (that you enjoy!) to hand. Maybe it’s chilled water, maybe it’s a pot of tea, maybe it’s a sports drink, it doesn’t matter too much. Even coffee is actually fine, by the way (but don’t overdo it).
2. Make a personal rule: “I will always make time for hydration”. That means, if you’re thirsty, have something with water in it now. Not when you’ve finished what you’re doing (unless you really can’t stop, because you are a racecar driver mid-race, or a surgeon mid-operation, or something), but now. Do not postpone it until after you’ve done some other thing first; you will forget and it will keep getting postponed. Always make time for water.