We’ve all been there, that creeping headache to remind us that we’ve not grabbed a drink for a couple of hours.  We seem to have an idea of how much water we should drink on a daily basis, but we don’t always hit that target.  Sometimes if we know why we need to do something it’s easier to include it in our daily routine, so let’s take a look at why fluids are so important to us, how much we really should be drinking, especially as we age and some top tips to increase intake.

What Is Water?

Water is essential for life. It really is that simple.  Humans can survive for a relative number of weeks without food, but they cannot go without fluids for more than two to three days.  Generally, water makes up around 60% of body weight (ranging from 40-75%) and is essential for the correct and efficient functioning of all cells in all bodies. 


  • acts as a lubricant for joints and eyes,
  • is the main component of saliva,
  • provides the medium in which most things occur in the body,
  • acts as a cushion in the nervous system,
  • helps get rid of waste,
  • helps to regulate body temperature.

Total water intake comes from three usual sources:

  • Water present in food,
  • Metabolic water,
  • Drinking water,

The amount of water present in food, depends on the type of food it is.  It is usually less than 40% in cereal products, 40-70% in hot meals, more than 80% in fruits and vegetables, and approximately 90% in human breast milk and cows’ milk.

Metabolic water is the water produced during the processes that occur in the body when metabolising fat, protein, and carbohydrates with fat producing the highest quantity of metabolic water.

It is estimated that roughly 20% of water consumed is from food, and the remaining 80% from beverages.  Whilst it is not necessary to drink only pure water, it is a beneficial choice. Other drinks such as squash, fruit juice, tea and coffee contribute to daily requirements too.

Other Beverage Choices

When considering other beverages to contribute to our daily hydration, there are a few notes to make.

Frequently consuming beverages containing sugar like fruit juices and sugar-containing fizzy drinks can increase the risk of dental issues and influence our energy balance. 

Whilst caffeine is a mild diuretic, drinks that contain caffeine (such as tea, coffee, cola) do in fact contribute to fluid intake under normal circumstances.  

With alcoholic drinks, the dehydrating effect can be greater, depending on the type of drink consumed. Spirits consumed alone can contribute to dehydration.


Dehydration occurs when more fluids leave the body than enters it. 

We routinely lose water through:

  • Breath – humified air leaves the body,
  • Sweat to cool the body,
  • Eliminating waste by urinating or bowel movements (increased risk in cases of sickness/diarrhoea). 

The body is incredibly nifty in that it can monitor how much fluid it needs to function.  The thirst mechanism tells the body to drink more when it is running low.  Hormones also tell the kidneys to limit how much water is lost in the urine too (which is why dark urine is a sign of dehydration).

Signs of Dehydration:

  • Thirst,
  • Reduced urine output,
  • Dark urine,
  • Dry mouth,
  • Lightheaded,
  • Muscle cramps,
  • Palpitations,

How Much Do We Need To Drink?

The general school of thought is that we should drink 6-8 glasses of fluid per day.  But depending on your glass size, this isn’t always that helpful – so it equates to around 1.5-2 litres per day.  But the amount we really need to drink varies from person to person, depending on age, time of year, climate, diet and the amount of physical activity we do. 

Water requirements are increased in hot climates and when physically active. 

Our age influences our hydration status for a number of reasons.

  • We have less water on board,

Around 60-70% of total body water is inside our cells in what we know as the ICF (intra-cellular compartment). 

Muscle cells contain a large portion of our ICF volume which means muscle mass influences our total body water levels. 

As we age, we are faced with muscle loss, so it’s no surprise that our total body water volume declines too.

Whilst we can try to maintain as much muscle mass as possible, it does mean our fluid reservoirs are a little depleted as we age, so we need to ensure we are hydrating well.

  • We may excrete more water through urine,

Kidney function can deteriorate as we age, meaning less concentrated urine can be produced, leading to more free water being lost through urination. 

Hormonal changes may also affect how well we hold on to water too.

  • Thirst sensation can change,

It seems that as we age our sensation of thirst is less obvious than when we were younger.  For the most part, on a day-to-day basis, we are able to drink sufficient fluids for normal function, but if we are challenged through heat or exercise, our thirst sensation struggles to keep up.  This means our ability to rehydrate is compromised.

Can We Drink Too Much?

Drinking too much water can lead to what’s known as water intoxication, which means that the sodium level in the blood gets too low.  This is a regular feature in many endurance athletes because whilst they are taking fluids on board, they aren’t replacing lost electrolytes which are essential to many functions in the body.  Signs of an electrolyte imbalance include muscle cramps, dizziness, irregular heartbeat and confusion. 

Top Tips for Staying Hydrated:

  • Glow up your water – add a slice of cucumber, lemon, lime or sprig of mint!
  • Grab your gin glass, pop in some frozen berries and pour sparkling water over the top!
  • Keep a bottle of water at your desk!
  • Always order some table water if you are out for a meal!
  • Get into a routine – if there is something you do every day, add drinking a glass of water to the start or end of the task.  Habit stacking is a great way to make changes!

Let us know how you keep hydrated. 

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