As funny as it may be to think, we are all just watery creatures living our lives on a watery planet. Nearly all living things are made of roughly 70% water—even humans. With this knowledge, it only makes sense that our hydration levels are tied to our physiological functions and performance.
To put it simply, we need to be well-hydrated to keep ourselves in tip-top shape. In this article, we’ll go over the benefits of adequate hydration, how much water science says you need to drink, and what happens if you don’t drink enough water.
Hydration and Performance
In any setting, adequate water intake is essential in bringing out your best performance. It may be pretty dramatic to say, but your hydration level impacts nearly all the systems in your body.
In athletes, water loss equal to 2% of the body weight is enough to have significant, observable damage to physical performance.1 Moreover, as the body gets dehydrated, it’s not just the physical body that becomes sluggish, but the mind as well.2 The unfortunate combination of physical and mental lag is a recipe for injury.
This emphasizes the need for adequate hydration. Aside from physical and mental response times, water maintains blood volume and regulates blood pressure. It’s also primarily responsible for the regulation of heat, which is vital in exercise.
Exercise raises the body’s core temperature, and the circulatory system brings that heat up to the surface to be dissipated by sweat. Without adequate hydration to regulate the body’s temperature, an athlete is likely to overheat and drop out of a game sooner than they’d like to. Without the thermoregulatory function of water, athletes are more likely to suffer from heatstroke, heat exhaustion, and cramps.3
How much water do you need to drink?
You’ve probably heard of the 8×8 rule, which says that we must drink eight ounces (around 237 millilitres) of water eight times a day to be adequately hydrated. It’s an easy, straightforward rule to hydration, but how accurate is it?
Photo by Cats Coming
Not that accurate, as it turns out. While it is a handy little slogan to remind people to drink water, there is no scientific evidence supporting this rule.4 That doesn’t mean it’s not helpful. Drinking eight glasses of eight ounces (237 mL) of water will total to roughly 1.90 L of water a day. It’s a good baseline for getting at least some amount of water in your system.
The body’s need for water intake depends on how much water it loses, and water loss can be highly variable in people. It’s not just urine, tears and sweat, which are collectively termed ‘sensible’ water loss. We also lose water through ‘insensible’ water loss (i.e., respiration and skin evaporation).5 Physically active people in warmer climates lose a lot more water than sedentary people in cold countries.
If you look into multiple references on the internet from various authoritative sources, there is no single value recommended for plain water intake that applies across global populations. Any value you find is roughly estimated at best. Even the World Health Organization and Center for Disease Control and Prevention have had trouble determining how much intake to recommend.6,7
What kind of water should you drink?
Is tap water safe to drink? Well, it depends on location. Is tap water safe to drink in Australia? Yes, absolutely.8 You can drink tap water or opt for bottled water according to your preference to taste.
Photo by Jacek Dylag
What’s the best drink for dehydration besides water? You’ve still got a lot of options if you prefer drinks with a bit more pizazz. Sparkling water, flavor-infused water, and plain coffee and tea are good options. So are milk, milk alternatives such as soy and almond, and fruit and vegetable juices.9
How will you know if you’re drinking enough water?
Fortunately for us, we come with an inbuilt hydration sensor. Thirst is the regulatory mechanism responsible for maintaining the body’s fluid balance. When we lose water, the blood becomes concentrated with solutes. An area of the brain (specifically, the hypothalamus) detects this change and increases thirst to stimulate water-seeking behavior.10 So when you get thirsty during training, make sure to get at least a few sips in on your break.
As long as you listen to your body and drink water when your body signals you to, you should be adequately hydrated. Another method to see how well-hydrated you are is to look at the colour of your urine. Take this chart below as a handy little reference guide.
Photo grabbed from The Sacramento Bee
The Institute of Medicine recommends at least 2.2 liters for women and three liters for men.11 If you have some trouble reading your body’s cues for water, or if you just want to be more hydrated in general, then these are decent amounts of intake to aim for.
What happens if you don’t drink enough water?
They say that people can survive without water for roughly three days. However, several factors affect this measurement. Aside from sensible and insensible water loss, every human body is variable in how it uses water and how much water it needs.
So, what happens if you don’t drink enough water? Since the body is 70% water, it only makes sense that dehydration affects the entirety of the body and its systems. The most overt symptoms of dehydration are thirst, a dry mouth, sunken eyes, and decreased skin elasticity.12
With the loss of hydration comes decreased blood volume. The blood thickens and becomes more concentrated, and through a series of hormonal mechanisms results in increased blood pressure. People who are chronically dehydrated develop hypertension and consequent kidney problems as they age because of this.13
Can anyone die due to dehydration?
Yes, severe dehydration can cause death. In extreme cases of dehydration, the blood volume drops lethally. The failing circulatory system fails to deliver nutrients to the organs. The unfortunate result is circulatory shock and death.
We know that anything too extreme is terrible for our health, but what about the other extreme end of hydration? Well, read on.
Can you drink too much water?
Some people drink water to lose weight. And well, there’s nothing to lose and so much to gain in drinking water. Studies have shown relationships between increased hydration and more significant weight loss.14 Having established that drinking water is a good thing, here’s another question: can you drink too much water?
Photo by quokkabottles
And the answer is: yes, you can. Overhydration dilutes the blood and results in a condition called hyponatremia. Hyponatremia is characterized by nausea, vomiting, confusion, headache, and extreme cases, cramps, seizures, and coma.
However, it’s not a typical occurrence in healthy people with normally functioning kidneys and doesn’t happen under normal conditions. Excessive water intake is possible in patients with medical conditions increasing the body’s tendency to retain water or affecting the kidneys’ ability to eliminate it.
In healthy adults, hyponatremia can occur as a result of prolonged exercise. We lose electrolytes when we sweat. The effects of losing electrolytes are negligible under normal conditions. However, extreme conditions are another conversation entirely. For example, in the case of marathoners, the electrolyte loss can be so great that any water intake may result in over-dilution of the blood. This over-dilution is medically referred to as Exercise-Associated Hyponatremia (EAH).15 It explains why the best way to hydrate during prolonged exercise is with electrolyte-rich drinks such as sports drinks and electrolyte water.
Even in athletes, over-hydration is a very rare incidence. The benefits of adequate hydration far, far outweighs the risk, so don’t skimp on water and drink as much as you can to keep your body healthy.
When is it time to choose sports drinks?
Photo grabbed from John McArthur
Have you ever wondered about why we burn calories? It’s because when glucose is broken down to a usable form of energy, it generates heat. The rate of heat generation increases exponentially during exercise due to increased energy demand. The body’s core temperature rises, circulation brings heat to the surface, and we sweat to dissipate that heat. Through sweat, we lose water and electrolytes, which are essential for optimal functioning.
In the case of exercise, therefore, you may benefit more from sports drinks than regular water. Sports drinks contain carbohydrates, water, and electrolytes in varying levels, and they are categorized as such:
- Hypotonic drinks are formulated to rapidly replenish fluid loss. With electrolyte concentrations lower than that of the body, it is easily absorbed in the digestive system. Hypotonic drinks are suitable for athletes who require fluid replenishment without the carbohydrate boost, such as bodybuilders.
- Isotonic drinks replenish fluid loss relatively quickly while providing a modest carbohydrate boost. This type of sports drink is the most popular choice for most athletes. Long-distance runners and those who participate in team sports are a few examples. Isotonic means that this category of sports drinks contains similar concentrations of electrolytes as can be found in the body.
- Hypertonic drinks contain higher electrolyte concentrations than the body does. Hypertonic drinks are not typically recommended during exercise. Instead, they can be helpful after a workout to supplement carbohydrate intake and replenish glycogen stores.
Each type of sports drink is digested and absorbed at varying rates. You can learn more about them here.