Even if you’re not diligent about drinking water, you’ve probably heard that eight glasses is the target.
Everyone from glowy-faced supermodels to mums will tell you drinking this magical amount of water keeps your complexion clearer than an Alpine stream, wards off headaches and ensures all your organs are chugging along happily.
However, the amount of water we need to drink is not necessarily that straightforward.
“As a rough estimate, The Australian Nutrient Reference Values recommends about 2-2.5 litres,” explains Professor Tim Crowe from Deakin University’s School of Exercise and Nutrition Sciences.
This equates to about eight glasses a day, but as with almost anything health-related there’s no ‘one size fits all’ approach to water intake. A number of factors can influence how much an individual needs, including the climate they live in, body size, diet, and in particular, how physically active they are.
“For every hour you’re working out, you should be adding on an additional litre of water,” Sydney-based personal trainer Kirsty Welsh recommends.
The ‘eight glasses a day’ figure is believed to have originated from a 1945 statement from the US Food and Nutrition Board of the National Research Council. The Board members wrote: “A suitable allowance for adults is 2.5 litres daily in most instances. Most of this quantity is contained in prepared foods”.
Clearly the 2.5 litre figure has stuck in popular memory – but it seems the second half of that passage has been drowned out over time. For this reason, people might assume their daily fluid intake needs to come from water specifically, even though they’re being hydrated in other ways.
“[The daily intake] can be tea, it can be milk, it can be fruit juice and it can be coffee. It’s a bit of a myth that coffee dehydrates you – you get loads of water in your cup of coffee and you only lose a small amount from caffeine,” Professor Crowe says. Food can also contribute to your fluid intake, particularly fruits and vegetables.
Of course, it’s important to remember that water is a more nutritious source of fluid than some other beverages because it doesn’t contain sugar or additives. If you find water hard to drink, Kirsty Welsh recommends adding a lemongrass teabag, or some fruit and herbs to add flavour (her favourite combination is cucumber, mint and lemon wedges). Herbal tea is another healthy way to stay hydrated.
Although it’s great to be diligent about chugging H2O, it is also possible to overdo it; if you’re a regular, otherwise healthy person, four litres in a day is pushing the upper limit.
According to health experts in a recent Daily Mail report, excess sweating and disturbed sleep are some possible outcomes of consuming too much water. In more extreme cases something called ‘water intoxication‘ can occur, as over-hydrating disrupts the body’s normal balance of electrolytes.
“The symptoms that [water intoxication] presents – you actually feel a bit drunk to start with, it causes blurred vision, you can feel light-headed, you can have poor muscle coordination. And that can progress enough that your brain swells, the pressure builds up and that can be fatal,” Professor Crowe explains.