How Much Water Do You Need A Day? It’s Not That Simple.
You’ve probably seen this humungous gallon-sized water bottles with the motivational inscriptions on the side. I think they look like a barrel, hence my nickname for them: The Barrel.
But should you be guzzling that much water every day? How much water do you need a day?
Don’t head to Amazon to buy your Barrel bottle just yet!
I get the ‘how much water should I drink?’ question all the time, and honestly, it’s not a one-size-fits all answer.
What does fluid do for us?
The role of fluid in our bodies is to promote normal circulation, digestion, elimination, to lubricate our joints, regulate temperature, protect the spinal cord and brain, help kidneys function properly, and also to replenish fluids lost with sweat, breathing, poop and pee.
We’re composed of around 60% water, so obviously, we need to be mindful of getting enough fluids to keep that balance.
We lose around 1-1.5 litres a day from urine. Another 3 cups or so is lost every day from a combination of breathing and sweating.
Things like having a fever, exercising strenuously, or being at a high altitude or in a hot climate make that 3 cup number jump even higher. Males typically need more fluids than females.
The symptoms of dehydration
If you’re not drinking enough, you’ll probably feel it: symptoms of dehydration include lightheadedness, dizziness, dry mouth, and headaches.
You’ll also feel thirsty. Of course.
Is it true that you’re already dehydrated once you’re thirsty?
It looks that way. But it’s not a big deal – just take a drink to rehydrate yourself. Obviously, you don’t want to ignore your body’s thirst cues.
About that 8 glasses a day thing.
This recommendation is actually from 1945, and it isn’t based on any research that I can find. We’ve come to understand a few things since then.
First off, a significant amount of our fluid intake can come not from what we drink, but from what we eat. Soups, juicy fruits and vegetables (celery and cucumber, anyone?), and even ice cream all count.
So does coffee, which wasn’t always the case. When I was in nutrition school several decades ago, we were told that every cup of coffee should be balanced out with a cup of water.
Nope! Not necessary! Not that I recommend getting your entire fluid intake from coffee.
Or booze, for that matter. It counts towards your fluid intake, but please…just don’t.
Can you drink too much water?
For sure, but it doesn’t usually happen. You’d have to drink over and above the amount of fluid that the kidneys can deal with, which is around 1 litre per hour. Will you keel over if you chug a litre of water at one time?
But anything over 20 litres a day is probably a bad idea. I feel like this should be obvious, because that’s a LOT of water.
People who get water toxicity (yes, it’s a thing) generally have some sort of issue with their thirst mechanism. For example, the drug ecstasy, otherwise known as MDMA, can inhibit urination while also increasing feelings of thirst. The result is hyponatremia, which is the dilution of sodium in the blood.
This can cause the cells to swell, and also lead to confusion, seizures, and death.
There are a lot of false claims that are made about water, like many of the ones on this infographic:
Let’s tackle some of them.
Erases wrinkles and makes skin clear and glowing
In the assessment of a person’s hydration status, we sometimes use a skin turgor test. This is when we pinch the skin on the arm and see how long it takes to snap back. The longer it takes, the more the person is dehydrated.
So maybe the ‘water plumps up your skin’ thing is true. But as studies suggest, only if you’re dehydrated. You don’t need a barrel of water to get the effect.
As far as the claims made about water erasing wrinkles? Nah.
If drinking water could erase wrinkles and make your skin glow, nobody would ever age.
It’s pretty much just common sense. But here’s an interesting fact: we don’t know if drinking water even affects the condition of the skin. It seems as though dry skin is caused more by external factors like sun and wind, not by dehydration.
Also: wrinkles are not caused by lack of water. They’re influenced by genetics and lifestyle.
So next time an influencer talks about drinking a barrel full of water to make her skin glow, you’ll know she’s full of it.
Detoxes the body
This one is everywhere – I even found it on a legit medical site, but really – it’s a bit of an overreach.
Here’s how it works:
The kidneys filter waste out of the blood. Your entire blood volume will go through your kidneys around 40 times a day. Hard workers, those kidneys.
Being adequately hydrated helps the kidneys do their job. Being chronically dehydrated can actually damage your kidneys.
So indirectly, drinking water helps ‘flush out’ toxins.
But drinking MORE water than you need doesn’t help the kidneys do a better job of toxin flushing.
I was once told by a fitness instructor that our bodies can’t burn fat efficiently unless we’re properly hydrated during exercise.
In her defence, this was in the 90s. We know better now.
I’m good with saying that if you’re dehydrated, your body is probably less efficient in everything. But there is no research in humans that proves dehydration inhibits fat burning.
And it goes without saying, that lemon water/ACV water/citrus water are also useless in this regard. So is alkaline water (read my post about alkaline water here).
As far as weight loss, there are a few studies that suggest that drinking before meals has the transient effect of reducing consumption. However, these studies are small and on specific groups of people (obese and middle aged, industry-sponsored and (50 ‘overweight girls’ with no control group and unremarkable results)
Ughhh this one. People everywhere are drinking ice water, thinking that they’ll burn more calories as their bodies warm up the water.
The truth is that drinking ice water does increase the metabolic rate, but the total increase burns only around 8 calories per cup of water – versus room temperature water.
It’s up to you – do you want to freeze your butt off all day for an extra 60 calories?
How much water do we need?
I’ve heard a lot of trainers say we should be drinking half our body weight in ounces. For a 150lb person, that would be 75 ounces, or almost 2.5 litres.
When I worked in clinical nutrition, I used to multiply a person’s weight in kilograms by 25 to get a rough estimate of what they needed daily in fluid.
The National Academies of Sciences, Engineering, and Medicine recommends that females get 9 cups of fluids a day, and for males, 13 cups.
This doctor recommends around half to one whole cup of fluid every hour that we’ve awake. That’s around 8-16 cups. Nothing out of the ordinary.
These are all guidelines, but I don’t recommend counting cups and ounces of fluids.
The best way to determine whether you need a drink (besides being thirsty), is to rely on the color of your urine.
Is it clear? Dark yellow? Medium yellow?
Colorless urine means you’re definitely hydrated, and can relax a bit on the fluids.
Medium yellow urine is good.
Syrup-colored or dark urine means you need to drink something.
Easy. No need to obsess over it. Like anything you consume, your fluid needs change day-to-day, depending on your environment and activity levels.
So, do you need The Barrel aka 3 litres of water a day?
Probably not. But if it’s motivating to you, go right ahead. Just don’t drink it all at once.