Should we be drinking 2 litres of water a day?

By Amanda Johnson 06/06/2012

According to an editorial published today in the Australian and New Zealand Public Health Journal, the recommendation to drink 8 glasses of pure water appears to be an over-estimation of requirements.

This advice by Spero Tsindos from La Trobe University in Australia is nothing new — but does stem from misunderstandings about fluid recommendations. Of course water is a healthy drink and a great way to re-hydrate — especially on a hot day or after exercise or activity. However, the current recommendation in New Zealand, according to the Ministry of Health Food and Nutrition Guidelines for Healthy Adults is to ‘take an amount of fluid equivalent to 6-8 glasses of water per day’. Australian guidelines also recommend consuming 8 glasses of fluid daily.

The misunderstanding about the difference between pure water and fluid has (according to the editorial) driven a steady growth in bottled water over the years — thirty years ago you wouldn’t have seen a water bottle anywhere — but now it is almost a fashion accessory. According to Spero Tsindos, “as tokens of instant gratification and symbolism, the very bottle itself is seen as cool and hip.’

It is of course very important to maintain fluid balance and to drink water when required. However, all fluids actually count — including water, milk, juice, tea and coffee. We do need to remember though that some fluids (sugary drinks and juices) contain a lot of sugar so should be limited for that reason. Also, for those susceptible to the effects of caffeine, drinks such as tea and coffee should be limited. As well as drinking fluids we should also remember that a number of foods that can contribute to our fluid intake — particularly vegetables and fruits — and these foods have the advantage of providing extra nutrition in the form of vitamins, minerals and fibre.

So, do you need to drink bottled water? Well, if you want to that’s just fine, but remember that water straight out of the tap, along with other fluids and watery foods, is just fine too.

For more information the British Dietetic Association have a nice summary of how to meet fluid requirements. Their advice — as long as your urine is a nice pale straw colour, you should be OK!

0 Responses to “Should we be drinking 2 litres of water a day?”

  • Goos points Amanda. I work with Nephrologists and, amongst other things, model fluid retention. Drinking 2 L a day, let alone of one beverage alone (as you nicely put it), is overkill. Most of that will be urinated. The kidneys’ control of the proportion of water in our bodies is extremely sensitive. Here’s some approximate figures from Prof Zoltan Endre (my collaborator and boss) found in “Essentials of Human Nutrition” Ch8 Oxford Uni Press 3rd edition.
    Water in the body – 35 to 45L (~60% of body weight for a male, 55% for a female).

    Under normal circumstances:
    Daily water intake:
    From Solid Food (i.e. present in the food as it is eaten): ~ 1L
    From metabolized food (i.e. produced by oxidation): ~0.4L
    Drunk: ~1L
    Total 2.4 L

    Water loss
    “Insensible loss” (evaporation from skin and breathed out): ~0.8L
    In Faeces: ~0.1L
    Sweat: ~0.1L
    Urine: ~1.4L (minimum to get rid of waste is ~0.6L, the rest is because of consumption of water).
    Total 2.4L

    Simply put, even at 1L a day most of us are drinking more than strictly necessary to maintain the right fluid balance in our body. If we do that, the kidneys will get rid of the rest.

  • Thanks John for those comments, and for breaking down intakes and losses.

  • Thanks, John – might point those of my students who firmly believe in the 8 glasses a day thing, over here 🙂