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How much water do you need to drink per day?

We all know we need to drink water to function at our best, but how much do you actually need? Is the old advice of ‘eight glasses a day’ really the right amount? How does the recommended amount change if you’re doing heaps of exercise? What about water content in things like fruit and vegetables – does this count as part of your daily target?

Both lifestyle and environmental factors play a part in how much water we require, explains Katie Lacy, a senior lecturer in nutritional science at Deakin University.

Why do our bodies need water?

Water is essential for humans – without it we can’t function, Dr Lacy explains.

We require water for many functions including digesting food, absorbing nutrients from food, eliminating waste products from our body and regulating our body’s temperature.

The body has nowhere to store water like it can with other nutrients, and we lose water through our waste as well as our lungs and skin. That’s why it’s vital we consume enough water each day.

‘Water is considered an essential nutrient, something that we need to consume because it is required in amounts our body cannot make,’ Dr Lacy says. ‘It is vital we replenish water losses for our body to function correctly.’

What are the current water intake recommendations?

Men and women have recommendations that include and exclude foods, Dr Lacy explains. ‘We can get significant amounts of water from food – some vegetables are actually 95% water.’

Recommended water intake for adult men aged 19+ years

  • 2.6 litres per day from fluids, and
  • 3.4 litres per day from both food and fluids.

Recommended water intake for adult women aged 19+ years

  • 2.1 litres per day from fluids, and
  • 2.8 litres per day from both food and fluids.

Note: women who are pregnant or breastfeeding have higher recommendations.

However, ideal water intake does differ depending on individual needs.

‘While we have these recommendations as guides, they are not intended to be set targets for each of us as individuals to achieve, as daily water needs vary from person to person,’ Dr Lacy says.

Rather than focusing on a specific number of litres or cups to drink, a helpful indication of how hydrated you are can be found by the colour of your urine.

The healthdirect urine colour chart is a handy guide.

How does your environment and level of activity change your water needs?

There are various factors that can alter the amount of water an individual requires, Dr Lacy explains.

‘Variations include things like physical activity, environmental conditions like temperature and humidity, as well as individual metabolism,’ she says.

While we all know how important it is to consume water as required to avoid dehydration, it’s also important to avoid over-hydrating because this can lead to water intoxication (hyponatremia). Both are serious and life-threatening conditions, Dr Lacy warns.

While it’s easy to drink water when you’re thirsty, but Dr Lacy says it’s also important to continue drinking water at other times too.

‘We tend to feel thirsty when we are already somewhat dehydrated so it’s important to consume water even if you’re not yet thirsty. An easy way to stay hydrated is to sip water throughout the day,’ she says.

If you’re doing a lot of exercise, Dr Lacy suggests the following:

‘The Better Health Channel has useful information on how to calculate your sweat rate if you want to work out how much to drink when exercising, but it can also be important to consult a sports dietitian for assistance with this.’

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Dr Katie Lacy
Dr Katie Lacy

Senior Lecturer in Nutritional Science,

Faculty of Health,

Deakin University

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