How Much Water Should You Drink?
Let evolution take the lead in your hydration habits.
Human bodies are made of water.
On average, about 70% of the human body is water. So, water is important for keeping us healthy.
How much water should you drink?
The modern “hydration industry” has convinced many people in the world of health and fitness that dehydration is a terrifying fate to be avoided at all costs.
Whether it’s a bandolier-style “hydration belt” or buckets of blue “sports recovery drink”, products that supposedly help us stay hydrated abound.
Should we worry about this? Before we freak, how much hydration do we really need?
Probably not quite this much.
Many factors affect our fluid needs.
The oft-cited guideline of “Drink X glasses of water a day” isn’t based on strong evidence. It’s one of those things that gets repeated often enough to become “well-known”.
The science doesn’t actually support a one-size-fits-all “drink rule”.
Each person’s individual fluid needs will depend on things like:
- Sweating: Obviously this is an important part of exercise. Sweat a lot, and you’ll need to replace more fluid (and electrolytes; see below).
- Body size: Smaller adults have a smaller volume and surface area. Thus, they lose relatively less fluid than larger adults via respiration and sweating. (However, children can become dehydrated easily.)
- Climate, humidity, and altitude: Dry, hot climates and/or high altitudes suck fluid away from our bodies faster.
- Salty food: We take in salts from our diets. When this happens, we may retain water or feel thirstier, and want to drink more. (The same is often true of sweet foods.)
- Alcohol: Alcohol makes us lose water at first, and then we often feel dehydrated and thirsty.
- Hormones: If you’re a woman of reproductive age, your hormones will change your body water levels throughout your cycle.
- Digestion and excretion: If you’re finding it hard to poop, adding more water will help move things through. And, if you’ve had diarrhea or vomiting recently, you’ll definitely want to replace that lost fluid.
For sure, water and proper fluid balance is pretty important for life. You can keep it simple, not over-think, and not over-drink.
Start with a simple set of daily practices. Work on doing them consistently:
- Drink when you’re thirsty, plus a little extra. Have a few extra sips or swigs here and there, just to boost the signal.
- Have a glass of water with your meals. Taking sips of water between bites can slow you down, and help you eat mindfully.
- Help yourself remember to hydrate. Leave a glass by the bathroom or kitchen sink, and have a glass each time you pass by. Or put a water bottle by your workstation.
- If you feel hunger or cravings, try having a glass of water first, to see if what you’re feeling is thirst, rather than hunger.
- Include fruits and vegetables in your diet, which also add water.
Simple practices like these can support a habit of drinking water regularly throughout the day. Drinking water regularly every day is the only guideline that most people will need in order to stay hydrating.
Most of the time, there’s no need to be fancy or too precise.
Add some extras if you need them.
- are very active (for instance, your workouts are intense and last longer than 60-90 minutes);
- are in a hot and/or dry environment, and/or at higher altitudes;
- tend to sweat a lot when you move around; and/or
- consume alcohol regularly (which is dehydrating),
Then you may want to consider drinking more, and adding supplemental electrolytes (dissolved salts such as sodium and potassium).
“Drinking more” could mean, for example:
- Follow the basic guidelines above of drinking water throughout the day.
- When you’re exercising, drink about 0.5-1 liter (1-4 cups) of water per hour of physical activity.
- Drink about 0.5-1 liter (1-4 cups) of water in the hour or so afterwards.
Unlike many biological stimuli, we don’t “adapt” to dehydration. We can’t “train” to become better at being dehydrated. We must replenish those lost fluids.
Consider adding some electrolytes for longer workouts, or training sessions where you lose a lot of water (and thus might be drinking more).
Sodium tells your body to hang on to the water it has, rather than dumping it overboard. It also helps to maintain blood pressure and electrolyte balance, and allows organs, muscles and nerves to work properly.
If you’re drinking a lot of water, it’s a good idea to add electrolytes, particularly sodium.
Drinking enormous amounts of water too quickly (in the neighborhood of 2-3 L per hour for a few hours), without replacing electrolyte/minerals properly, can lead to electrolyte imbalances in our body.
For most people, this situation (known as hyponatremia) isn’t a problem. It generally only happens to endurance athletes who train for hours, sweat significantly (losing lots of sodium in their sweat), and drink gallons of plain water without ever replenishing their sodium levels.
To add these electrolytes:
- Salt your food normally. If you’re craving salt, go ahead and have some. In women especially, salt cravings are often there for a good reason. If you’re out on the trails and have food with you, toss a little salt into your trail mix.
- If you’re drinking a lot of water, make sure you’re also consuming electrolytes along with it. You can choose sports drinks with electrolytes included, or look in your local drugstore for a lower-calorie powder such as Pedialyte, which is designed for fluid and electrolyte replenishment.
- Try natural mineral waters, such as San Pellegrino or Gerolsteiner. These have dissolved minerals in them already, and are also a nice substitute for soda.
Find your “sweet spot”.
Experiment with your fluid intake and find the water balance that works for you and your needs.
If you notice persistent thirst or salt cravings, talk to your doctor.
These can both signal underlying health concerns.