Water is essential for life. You can survive roughly 3 weeks without food, but only about 3 days without water.
The average human body is made of roughly 60% water. This percentage varies with body composition - lean muscle contains more water than fat, however it’s usually between 45–75%.
So clearly, drinking water is important...but why? Read on to find out!
What does water do for the body?
Water has numerous roles in the human body, including some of the following:
Cognitive performance - Proper hydration aids healthy cognition. Mild levels of dehydration can produce disruptions in mood, concentration, alertness and short-term memory. Dehydration is one of the leading causes for confusion and delirium in long-term care residents.
Gastrointestinal function - Adequate water consumption aids the digestive system to function smoothly. Dehydration can lead to constipation and contribute to other gastrointestinal discomforts.
Kidney function & bladder health - The kidneys regulate fluid balance in the body and require water for the filtration of waste from the blood, which is excreted via urine. Adequate water intake has shown to help reduce the risk of contracting UTIs (unitary tract infections) and kidney stones.
Heart function - Blood is more than 90% water and a hydrated heart is able to pump blood more efficiently, allowing oxygen to reach your muscles. When you are dehydrated your blood volume decreases, increasing your heart rate and blood pressure.
Thermoregulation - Hydration is crucial for the body’s process of temperature control. Water is lost through sweating, which is an important cooling mechanism during physical activity or in hotter climates.
Joint health - Water is a component of the lubricating fluid around the joints, which helps prevent joint friction.
Muscle building - Lean muscle tissue is around 75% water, hydration aids in the building and maintenance of healthy muscle.
What are symptoms of dehydration?
Dehydration occurs when your body uses or loses more fluid than it takes in, and your body is unable to carry out its usual tasks due to a lack of water. You will become dehydrated if you do not restore lost fluids.
It's likely that all of us have felt dehydrated at one point - and it's not a pleasant feeling. Here's some warning signs that you might be dehydrated:
Dark yellow and strong-smelling urine
Feeling dizzy or lightheaded
Dry mouth, lips and eyes
Urinating fewer than 4 times a day
Do you have to drink plain water for it to count?
Nope! Many foods and drinks contain a high volume of water, consuming them aids hydration.
Did you know the average watermelon is 92% water?
It’s estimated that food intake contributes to 20–30% total water intake, whereas 70–80% is obtained via drinks. This estimation is not fixed though, as it depends on the type of food and drink.
The most hydrating drink to reach for will always be water, although herbal teas, coconut water and fresh juice are some good alternatives when you want to mix it up.
Energy drinks and sugary carbonated drinks are not ideal drinks for proper hydration due to the sugar and caffeine content. Likewise, most alcoholic beverages have a dehydrating effect - the higher the alcohol percentage, the more dehydrating it will be.
How much water should you drink?
The average sedentary adult under temperate conditions should drink 1.5 L-2L of water per day. Although this amount changes when you factor in exercise levels and climate.
Generally, thirst sets in at 1% dehydration. So, in most cases thirst can still be a reliable mechanism for dehydration detection.
Monitoring your urine can often help you understand your hydration needs. The ideal colour is a pale straw to transparent yellow colour, some people describe it as a “champagne” colour. Completely clear urine may indicate you’re drinking a lot of water and you may want to cut back a bit.
Can you drink too much water?
Yes. Drinking too much water can cause hyponatremia (aka water intoxication), which is when you consume more water than your kidneys can excrete. This dilutes the electrolytes, especially sodium, in the blood. As the body's water levels rise, cells begin to swell. This swelling can cause an array of health problems, from mild to life-threatening.
Symptoms include: dizziness, nausea, headache, fatigue, confusion, unconsciousness (similar symptoms to dehydration!)
This is why endurance athletes need to properly account for electrolytes when rehydrating.
So, what’s a safe amount to consume? The kidneys can excrete 20–28L of water per day, but they cannot excrete more than 0.8 to 1.0L per hour, therefore some sources suggest not to drink more than this per hour under regular conditions (e.g. at resting state and in comfortable temperatures).
How does hydration affect sports performance?
Numerous studies have confirmed that performance can be impaired when athletes are dehydrated. Proper hydration during training or competition will enhance performance and prevent injuries associated with dehydration and sweat loss. Mild levels of dehydration during physical activity can result in increased fatigue, loss of motivation, reduced endurance and altered thermoregulation capabilities.
It is not uncommon for athletes to lose 6-10% of their body weight due to sweat loss during difficult athletic events. A decrease in performance in athletes is often observed in as little as 2% dehydration. Scientists at the Human Performance Lab in Indiana conducted a study which dehydrated athletes by 2-3%. In 1500m timed trials, performance fell by 3%. In 10k timed trials, performance fell by 7%.
In contrast, drinking too much water before, during, and after endurance events may cause sodium depletion (see above for hyponatremia).
When exercising in a hot environment, water loss through sweating can be up to 1–2 L per hour. Therefore, a general rule of thumb for hydration whilst exercising is for every 1hr exercise aim to drink an additional 1L of water (and up to 2L if in a hot climate or if exercising at high intensity). Don’t forget that if you’re sweating intensely, you’ll also be losing electrolytes, drinking a sports drink during endurance exercise is recommended. Just water is usually sufficient if exercising less than 1hr at medium intensity.
A great solution for many is to take a sports performance supplement with electrolytes, like Vivo Life SUSTAIN, which helps take care of hydration and electrolyte levels, whilst aiding muscle recovery at the same time as it also contains vegan essential amino acids, helping you work out for longer.
For endurance athletes it is recommended that they should drink beverages containing carbohydrate and electrolyte during and after training or competition. If you are just getting into endurance sport consult a sports nutritionist or trainer to calculate your hydration needs and to find out which sports drinks are right for you, as it will be unique to you.
Water keeps us alive, it’s imperative for health and physical performance.
Be mindful of your body’s cues and make sure you drink when thirsty. If you feel you may be dehydrated, try tracking your water consumption and aim for 1.5-2L water a day. Try spreading out your consumption e.g. 6-8 x 250ml glasses of water across the day. Ensure you are hydrating more when exercising and take into account electrolyte loss if you are in endurance sport.
If you are experiencing ongoing mild symptoms of, or are prone to either dehydration or hyponatremia, please contact your doctor. Seek emergency care with severe signs and symptoms, such as nausea and vomiting, confusion, seizures, or lost consciousness.