Key takeaways
  • Factors like body weight, age, exercise, and health can influence optimal hydration, so 2 litres of water per day may not be enough for everyone.
  • Proper hydration is crucial for regulating body temperature, supporting healthy skin, and aiding digestion and nutrient absorption.
  • On average, adults need 2.1 L – 2.6 L of water per day, but in certain conditions, such as high temperatures, exercise, or medication use, the total intake needs can be higher.

We’ve all heard the common recommendation to drink two litres of water every day. But is two litres really enough? Quite frankly, no it isn’t. You see, there are several factors involved in arriving at a recommendation of two litres of water per day for baseline hydration.

In this article, I am going to discuss how much water we really need to stay well-hydrated.  I’ll touch on some of the calculations used to determine adequate hydration, as well as many of the factors that influence loss of hydration.  I’ve also included some simple strategies you can start with today to assess your hydration, correct for dehydration, and remain well-hydrated every day.

Guidelines for hydration in Australia

According to the Australian Dietary Guidelines (2013),  the average daily turnover of water (i.e. water in, water out) for a 70kg person is approximately 4% of body weight, or 2.5 L – 3 L of water per day, taking into account fluid that is lost through urine, sweat, faeces, and the breath. 

These calculations are based on an average person, living in ambient temperatures and humidity, close to sea level in elevation, and not including fluid loss during exercise.  These calculations also assume that a person is of median age, not pregnant, and doesn’t have any predisposing medical condition that would affect fluid balance.

From this you can already start to see that several factors are going to influence optimal hydration for you as an individual:

  • Body weight
  • Age
  • Pregnancy or lactation
  • Exercise
  • Environmental temperature
  • Humidity
  • Health 
  • Medications

Why is hydration important?

Hydration is important for many reasons including helping to regulate body temperature, supporting healthy skin and aiding in digestion and nutrient absorption. 

Millions of metabolic and biochemical processes occurring in your body every minute of the day are carried out in an internal water environment and are dependent on proper hydration. 

Here are three key reasons to make sure you’re drinking enough water:

1. Hydration helps to regulate body temperature

Proper hydration is crucial for regulating body temperature because water helps to transfer heat away from internal organs and muscles to the skin's surface. 

When the body is dehydrated, it becomes more difficult for the body to regulate its temperature, and this can lead to heat-related illnesses such as heat exhaustion or heatstroke. 

2. Hydration supports healthy skin

Drinking enough water is essential for maintaining healthy skin because it helps to keep the skin hydrated and flush out toxins that can contribute to skin problems. 

Water also plays a crucial role in maintaining the skin's natural barrier function, which helps to prevent moisture loss and protects the skin from environmental stressors such as pollution and UV radiation. A well-hydrated skin barrier can also prevent the penetration of harmful bacteria and other pathogens that can cause skin infections.

Drinking water can also help to reduce inflammation and irritation in the skin. Skin conditions such as acne, eczema, and psoriasis are often aggravated by inflammation, and staying hydrated can help to mitigate these symptoms.

3. Hydration aids in digestion and nutrient absorption 

The average total body weight percentage of water in the average adult is estimated to be between 50-60% depending on age, weight, and gender. Estimations vary depending on the source, but this estimation is fine for the purpose of our discussion. 

In reality, the concentration of water in various tissues of the body varies significantly.  As you can imagine your toenails will have far less water in them compared to your brain.

What’s more important though, is where this water is found. 

In the body, water exists in three spaces, which are referred to as compartments.

  1. Intravascular compartment: Inside the blood vessels
  2. Interstitial compartment: Surrounding the cells in various tissues
  3. Intracellular compartment: Inside the cells

Water constantly moves between each of these compartments helping our body to maintain a healthy balance of minerals, nutrients, biochemicals and waste. 

Without proper hydration, your blood becomes “thicker”, your tissues “dry out”, and your cells lose their ability to function normally. Nutrients can’t get in, and waste products can’t get out.

How much water do we actually need?

Well as it turns out, an average adult, needs to consume 2.1 L – 2.6 L of water per day, in addition to water that is contained in food as a baseline. 

In high temperatures, low humidity, high elevations, during exercise, or if consuming diuretic foods and beverages (coffee, tea, energy drinks, alcohol), or with the use of certain medications, your total water intake needs can be significantly higher.

A simple formula to calculate baseline water intake is to divide your weight in kilograms by 30.

For example:

  • 60kg = 2.0 L per day
  • 70kg = 2.3 L per day
  • 80kg = 2.6 L per day
  • 90kg = 2.9 L per day

Remember though, this is your baseline, your starting point each day.  There are a few other things you should take into consideration, so let’s look at those now.

Maintaining proper hydration

Simple strategies to stay well-hydrated

As a functional medicine practitioner, chronic dehydration is one of the most overlooked factors I see in a person’s health picture. Here are some of the strategies I commonly share with patients to help them build healthy habits around water intake:

  • Hydrate first thing in the morning. Upon waking, consume a glass of water before taking any other food or beverage to replenish fluids lost during the night
  • Aim for baseline intake every day. Be sure to achieve your baseline water intake every day, by slowly consuming your water regularly throughout the day. Aim for approximately 1 cup or 250ml per hour for the first 10 hours after waking. After this time you can consume a smaller amount per hour to help prevent sleep from being interrupted by the need to urinate
  • Eat a healthy, wholefood diet. Eat a diet abundant in fresh fruits and vegetables which contain a good amount of water, along with minerals to maintain adequate electrolyte balance. Fried, dried, and microwaved foods contain far less water, as do many processed and packaged foods
  • Minimise diuretic beverages. Coffee, tea, alcohol, energy drinks, and sugary beverages will cause you to lose fluids through urine and faecal waste. If you enjoy your morning coffee, remember to follow it up with a shot of water
  • Drink more water during exercise. The Galpin equation recommends 2.2ml of water per kilogram of body weight every 15 mins of exercise that increases heart rate, breathing rate, or induces sweating
  • Manage dehydration with a low-glucose solution. If you do become dehydrated, use a low glucose-containing rehydration solution such as Sodii electrolytes, and continue to slowly drink your water until you are rehydrated. If you become significantly dehydrated for any reason, you should seek the advice of your health professional.

How do you know if you’re well-hydrated?

The most simple rule of thumb to determine if you are well hydrated is to look at the colour of your urine. In most cases, if your urine is faintly yellow or almost clear, then you should be good to go. You can use this handy online colour chart to help guide you.

If your urine is darker* - consume more water, or if you’re concerned, consult your health professional. 

*If you take vitamin B, it is normal for your urine to be a bright yellow for several hours after taking your supplement, wait 6-8hr after taking your supplement to assess your urine colour.

Stay hydrated, stay healthy

For some people, drinking two litres of water daily will be enough, and others will need more. 

Start by using the simple formula described above to calculate your baseline daily intake. Keeping in mind there are going to be a whole range of factors that impact your body's optimal hydration, including your weight, age, pregnancy status, exercise routine, environmental temperature, humidity, health status, and medications. Then gradually start to incorporate some daily habits to help you achieve your intake goal.

Of course, hydration is just one part of your health picture - but making sure you’re drinking enough water each day is one of the easiest ways you can take a positive step towards optimal health and well-being.

mark payne functional medicine practitioner wearing green shirt standing smiling
Mark Payne
Mark, with 30 years in health and education, specialises in health optimisation and longevity, cardiometabolic, digestive, and immune health, including HIV support. Awarded for research and teaching. Adjunct Fellow at Southern Cross University's National Centre for Naturopathic Medicine.
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Mark Payne
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{ "datePublished": "Nov 29, 2023" }