Why Hydration is Important

Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.


Being hydrated is critical to our health, and performance, especially if you are an athlete or exercising.

Water is the most important substance in the human body however it is often overlooked and neglected by us even though it is an essential nutrient.

The human body is made up of around 60% water according to the Journal of Nutrition, Health and Aging - and this clear liquid is one which is crucial to our health and well-being. 

In this article we shall look at why you should ensure your body is optimally hydrated.

  • Importance of hydration
  • Eating healthily
  • Physical performance
  • Concentration and motivation
  • Energy
  • Weight loss
  • Muscle function
  • Blood pressure
  • Circulation
  • Thermoregulation¬†
  • Sleep
  • Illness prevention¬†
  • Fluid requirements
  • Conclusion¬†¬†

The Importance of Hydration

When we hear people talk about hydration and drinking enough water, the common rule of thumb is to drink around 8 glasses of water a day, making up to around 2 litres of water overall. 

But why are we constantly told to drink water and keep hydrated? 

Water has many important functions in the body and the first thing we are going to do today is run through them to help you truly understand the importance of drinking enough water every day and maintaining optimum hydration.

Water protects your body 

The first function of water in the body is almost like a cushion. It keeps your organs and tissues surrounded with a soft layer to cushion them from any possible impacts.

Water also resides around your tissue, joints and sensitive organs to ensure that they stay at a regulated temperature and stay moist.

It acts as both an airbag of sorts and a lubricant for the body allowing it to run smoothly.

For athletes in particular, it is important to keep those places cushioned to avoid issues when impacted by stress. 

Water removes toxins 

One of the main functions of water in the body is almost like a waste disposal unit - ridding the body of toxins that may otherwise harm you by ensuring that your kidneys work efficiently.

When we sleep at night our bodies get to work and get rid of toxins such as fats, alcohol, bacteria and more. Water helps us rid our bodies of toxins in a few ways such as sweating, urinating, and defecating.

Without enough water, you could risk illness as the body will not be able to effectively rid itself of toxins and you may end up with constipation as highlighted by the UK's National Health Service, here. 

It helps us digest 

Healthy digestion is the absolute be all and end all for the healthy body and water plays a big part in this function.

Water aids in the breakdown of food we eat and allows us to metabolise the nutrients and get rid of the waste.

Without maintaining hydration levels you may end up with constipation and in severe cases you may have a digestive disease due to build up of food in the gut that gets infected. 

You won’t be dehydrated

woman drinking glass of water 

It might be obvious to point out that water stops us from being dehydrated - but did you ever stop to think what dehydration actually is and what it means?

Dehydration can lead to cell dehydration which then leads to dysfunction and cell damage notwithstanding the potential of being fatal. 

This is purely due to fluid losses overtaking fluid intake. This is known as a negative fluid balance.

When the body becomes dehydrated it is important for you to drink more fluids whether this be water or an electrolyte drink to bring back up those fluid levels and maintain healthy function once more. 

A such, the European Food Safety authority recommends daily water intakes of 2000ml for women and 2500ml for men.

Improved cognition

When it comes to clearing your mind and getting down to work whether it be an exam or your day job - brain power is a must.

Of course, we have spoken earlier about how water cushions and lubricate organs such as the brain - hydration also plays a huge part in our brain function.

Published research from the British Journal of Nutrition concludes that there is mounting evidence supporting the notion that hydration effects cognitive function and mood. 

Severe dehydration can result in defects such as short term memory loss.

Unlike the rest of the body, the brain is made up of 73% water so hydration is more crucial to the brain than anywhere else. If you are ever struggling to concentrate or work - take a drink of water and you’ll soon be able to clear your mind and get going. 

Water is good for your heart 

If you think about it, water is a major part of every fluid in the body and this includes our blood.

Blood is important in the body to help transport oxygen to every cell of the body and keep it healthy. Furthermore, your blood is pumped through blood vessels and arteries.

Dehydration is linked to arterial stiffnes, inflammation and blood vessel lining dysfunction as outlined by an article published in the Nutrients Journal, here.

These issues can lead to cardiovascular disease, and mild dehydration has been compared to smoking a cigarette as described by the lead scientist of a published study.

Our heart is the literal beating heart of the body and we must keep it healthy and strong throughout our lives. Particularly for those in sport or a demanding lifestyle such as military personnel.

Therefore, it is important to maintain a strong heart that can cope under immense pressure.

Maintaining hydration will not only help the rest of your body but it will keep your ticker going strong. 

There are so many functions of water in the body and it is important for us to understand them and the impact of them if we are to stay healthy and fit throughout our lives.

Now that we know some of the core functions of water in the body, it is time to see why water is so important for those who are in the sporting arena or for people in the military. 

First of all what are the main components in the lives of those who are healthy and fit? 

We need to eat healthy to fuel our bodies for physical success; we must keep the mind clear to allow for concentration; and we must be able to feed our muscles and joints the fuel it needs to grow and stay strong under pressure. 

So how will water help us with any of these things? 

Water can help you eat healthy

The first point we have to share about water is that it will make you eat a healthier diet.

Water itself is not like some magic drug that will make you choose kale over chocolate - however, according to studies water can make us feel fuller for longer (when drunk before meals) and can even curb our sugar cravings.

If you have been wanting to overhaul your eating habits for a while or if you are living a fitness lifestyle it is important to drink between 2-2.5 litres of water every day to keep the body happy. 

Often we are thirsty this can translate to the body in the same way as hunger does - and most of the time when you feel those hunger pains you don’t actually need food, you need water.

Furthermore, if you feel thirsty, the chances are you're already dehydrated according to Dr. Irvin Sulapas, a primary care sports medicine physician and assistant professor of family and community medicine at Baylor College of Medicine.

It is important to start drinking more water throughout your day to avoid the issue of these pains being mistook for hunger and eating more than you should.

By maintaining hydration throughout the day you will not feel as hungry and hence you’ll eat less calories, and less food overall. This will keep you more lean and healthy and will make a huge difference to your body.

Water maximises your physical performance 

why hydration is important

If you are an athlete or you are in the military it is more important than ever to stay hydrated and keep your body moist.

When you come to workout at the gym or out on duty it is important to bring some water with you that you can sip in small quantities throughout your session.

If you don’t sustain your levels of hydration during physical exercise you will not replace the fluid and electrolytes lost through sweating and this can lead to  homeostasis failure.

As you lose water, or indeed fail to replace lost fluids, it reduces the available blood flow and as a result decreases muscle performance. 

While everyone has different rates of sweat, once 2% of your body's water content is lost you will notice a reduction of performance, further losses can mean more severe effects as outlined by the Victoria State Government in Australia. 

Furthermore, losses during exercise can range from about 1 liter and up to 3 liters per hour depending on a number of factorsd which can include:

  • Climate
  • Fitness level
  • Gender
  • Clothing
  • Altitude
  • High protein diet
  • Fecal loss

Military Personnel

Not only are sodliers active on exercises and deployment, but they also carry lots of kit which adds further exertion. 

Sometimes, the military is active in regions that are very hot, and not normally where athletes would even train or compete. 

This increases fluid requirements and needs diligence by not only the individual soldier but also their leaders as findings demonstrate that soldiers operating in extreme heat can sweat 3 - 4 liters per hour and up 10 liters daily! 

This means to operate effectively, hydration must be taken seriously. You'll find jucies, and isotonic drink powders in your ration packs/MRE to help replensih carbohydrate stores and electrolytes. 

Being hydrated helps you concentrate and stay motivated 

Have you ever been working out and you suddenly start to feel a throbbing in your head and a dizzy feeling take over your body? Well, this is what dehydration feels like.

In order for you to perform the best you can in the field or in the gym your mind needs to be switched on and focussed on the task at hand.

When you don’t drink enough water or replenish lost water from your body you run the risk of the mind getting foggy, suffering from confusion, being angry, losinf focus and becoming stressed. The result is either plugging through it and not actually achieving much or having to stop..

Be sure to drink enough to ensure that you get the results you want. If you don’t make an effort to do this you won’t reach those all important fitness (and other) goals. 

military muscle testosterone booster banner

Water keeps your energy up 

As a follow on from the point above, it is important for you to maintain energy while working out otherwise you won’t be able to perform.

As a sporting individual you need to consider the impact that lack of water can have on the brain and in turn your body.

Energy levels are rooted partially in our body but also in the mind and as we become tired mentally it can make the rest of the body feel that way as the brain sends signals throughout.

Keep the brain switched on and ready to go by drinking plenty of water every day to avoid fatigue.

It helps us lose weight 

The main aim for people when looking to start on their healthy fitness journey is to lose weight and get lean and muscular. If you are one of these people and you are looking to perform as well as lose weight then drinking water regularly is essential for you.

As well as curbing your hunger pains, water can also do something magical and increase metabolysis and lipolysis. 

Our metabolism is a measurement of how quickly and efficiently we digest our foods. The people who have a high metabolism are often thinner than those with a low one and this is why when trying to lose weight it is important to increase it. 

There are several ways to increase the rate of your metabolism such as drinking coffee (due to the caffeine content) - but water alone is a great option.

Water is useful for the metabolism because it aids in digestion and makes it easier for our body to break down the food we eat.

If you drink plenty of water throughout the day your metabolism will stay running strong and you will get all of the important nutrients out of your food without the fuss.

Make sure that you drink a glass of water 30 minutes before eating to feel the true effects of this. 

Improve your muscle function 

Our muscles are like any other tissue of the body and need water to work.

Every cell that makes up your muscles needs enough water inside to keep it lubricated and maintain intracellular fluid osmolality.

Dehydration leads to muscular function deficits, therefore for adequate muscular recovery after exercise and to maintain strength, hydration is key.

Keep your blood pressure in check 

There are many things that can impact blood pressure: from cholesterol to iron levels and even stress.

Not being adquately hydrated can lead to low blood pressure as outlined by the , American Heart Association and this means that the blood cannot provide the organs and muscles with enough oxygen and nutrients. This can lead to shock.

Additionally, dehydration can lead to high blood pressure.

High blood pressure can lead to cardiovascular disease such as a stroke or a heart attack. Furthermore, high blood pressure runs the risk of possible kidney failure. 

Better circulation 

One of the things you may not have considered when thinking about physical performance is your circulation.

During every day life our heart pumps blood all around the body to provide oxygen to our cells and improve body function.

However, sometimes blood doesn’t properly reach our extremities and this is why in the cold many of us have stiff hands and feet due to lack of oxygen.

As an athlete proper circulation of blood around the body is essential to keep us healthy and allow for ultimate performance. Water helps to improve the flow of our blood by diluting it and this makes it easier for blood to reach those far off parts of the body.

Water keeps the body cool 

It is incredibly important as an athlete that you are able to regulate your body temperature and stop yourself from overheating.

When we workout our muscles release energy as heat and this makes our body incredibly hot - and our body provides sweat to cool the body down and keep the temperature at a safe level. 

Those that are dehydrated have shown to have a higher deep body core temperature compared to those who are hydrated in studies. 

For soldiers in particular, a lot of training and on site exercises will be in hot countries and this can take a huge toll on the body.

It is important for soldiers to drink enough water to regulate body temperature and prevent things such as heat stroke or high blood pressure. 

It helps you sleep 

It is important for anyone who is in the physical world to get a good night's sleep each night to allow the body to rest and recover for the following day.

Sleep is an important bodily process and we all need at least 8 hours a night to allow for things such as removing toxins from the body and repairing muscle and tissue. 

As a sporting individual it is important that you sleep to allow the body to rest in between workouts. It will give your muscles the time to recover and rebuild and in doing so you will prevent injury. 

A study published in the Sleep Journal found an association between short sleep duration and dehydration. 

Prevents illness 

One of the important benefits of drinking water for those who are working in the field of duty overseas is the prevention of illness.

When working as a soldier in different parts of the world and faced with a different environment there is always the risk of illness or chronic disease.

Evidence demonstrates that a lack of adequate hydration can lead to kidney stones, exercise asthma, urinary tract infections and stroke with some inconsistent evidence that keeping hydrated may help prevent colon and bladder cancer. 

Fluid Requirements

athlete drinking water

Fluid needs are a personal matter.

For example, John who plays soccer in the 'midfield' position may need more fluid throughout a game compared to Jared who plays in goal. This is because Jared is more stationary than John who may cover 10.5km during the 90 minutes game. 

Regardless of distance covered, Jared and John most likely will have different rates of sweat anyway, so it is still important to specify requirements for an athlete.

So, with this in mind, how do we know how much fluid John and Jared require?

It's actually quite simple to find out, and anyone can do it.

So, if you're involved in sports or have a very physically demanding role in the military or even in a civilian aspect and want to ensure you are optimally hydrated, you could do this yourself. 

How to calculate sweat rate

One way to know if you're hydrated is by checking the color of your urine. Now this is probably not possible to check when you are playing tennis or soccer, not without upsetting a few people. 

However, you can check this just before you play a game. So, ensure your urine is light in color, almost clear but with a hint of yellow. A bit like champagne but minus the fizz. 

Then you need some scales and potentially a bit of privacy to measure your current weight whilst naked. Log this figure. 

Next up, you should exercise for an hour that would replicate the intensity of a game of tennis, soccer, basketball, soldiering etc.

During this period, you should refrain from taking on any fluid. If you do, you need to ensure you know exaclty how much has been consumed, and make sure this amount is logged.

Once the hour has finished, go and weigh yourself naked again. Then subtract the second figure (post-exercise) from the initial weight (pre-exercise).

For example. Your pre-exercise weight maybe 200lbs(90.9kg). But, after an hour of exercise you may weigh 197.8lbs(89.9kg).

That's a difference of 2.2lbs(1kg).

Lost fluid equation

To put it simply, 2.2lbs(1kg) of weight lost equals a 'sweat rate' of 1 liter per hour.

If you work in metric measurements, this is very simple to establish. You literally convert the grams or kilograms to liters as explained by the Korey Stringer Insitute. 

For example, 250g of weight lost during exercise just means that 250ml/0.25l of fluid needs replacing.

However, if you only work in pounds or your scales only have the option of measuring in pounds, you have a little bit of math to do. Don't worry, it is not difficult. 

If you lose 3lbs of weight you just divide that figure by 2.2. This equals 1.36 liters.

Weight lost (lbs)/ 2.2 = sweat rate (fluid lost that needs replacing).

Are there any caveats?

Yes. If you have a particularly high sweat rate you may not be able to replenish enough fluid as the stomach can only absorb 1.2 liters of fluid per hour.

In this case, if it is possible, you should try and adjust either clothing or the environment to try to reduce sweating.

For instance if you exercise indoors see if you can either introduce a cooling system to reduce the ambient temperature or exercise outside if the temperature is lower.

Alternatively, you could wear fewer layers or different fabrics. 

why hydration is important

Can you over hydrate?

Yes. If you are a competitive athlete, it is advisable to establish your personal sweat rate so that you can be optimally hydrated and not go under or over your needs as both situations can cause hyponatremia.

Hyponatremia is when your sodium levels are very low. This electrolyte imbalance may negatively effect the following areas:

  • Blood pressure
  • Muscle function
  • Nerves
  • Body tissues

Furthermore, low sodium can also cause cells to swell with water which is particularly damaging to the brain.

Symptoms can include:

  • Headaches
  • Vomiting
  • Fatigue
  • Muscle weakness
  • Irritability¬†
  • Seizures
  • Coma

The Nursing Journal of 2005 explains that a sodium balance can be affected by simply being too dehydrated from excessive fluid loss or simply too much water gain. This drop in sodium pulls water into the cells.   

 A study published by Leeds Beckett University investigating hydration in English Premiership rugby players found that during the cooler climate (which reduces sweat and should also reduce the onset of thirst) some were taking on too much water. 

It was speculated that was an "exaggerated awareness" of dehydration or they were drinking to offset thermal discomfort. 

While their levels of hydration did not cause any negligible loss in performance, it higlights the need for athletes to understand their own 'sweat rate'.


Water is the lifeblood of our body, and it is crucial that we stay hydrated. If you are a sporting professional or military personnel you may need to employ the method of 'prophylatictic water consumption'.

This means you replace more fluid than lost and is generally not suited to those who lead a more sedentary lifestyle. 

Furthermore, thirst is not a good gauge of hydration. Bear in mind that respiratory fluid loss can range between 200-1500ml daily based just on the environment, and once thirst becomes noticeable, you are already in a dehydrated state. 

Therefore, to ensure that your health and fitness is in optimal shape, you need to ensure that so is your hydration. 

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