8 Glasses a Day – Where does that come from?

We have all heard about the importance of hydration for good mental and physical health, and one of the bits of advice that gets used a lot is ‘Drink 8 glasses a day’ – but where does that come from and is it an accurate estimate of how much water is required daily?

Where is the advice from?

It seems likely that the 8 glasses a day advice actually originated in the US – it likely stemmed from dietary guidelines published by the Food and Nutrition Board of the National Academy of Sciences in the 1940s, who claimed 2.5 litres of fluid should be ingested on a daily basis.

So, how accurate is the advice?

Well, unsurprisingly, our knowledge of nutrition and hydration has improved since the 1940s, but the answer is that it’s sort of accurate…ish!

The amount seems fairly arbitrary – and fails to take into account a number of factors… Including the difference in hydration needs from person to person. As with all nutritional needs, a large grown man with an intense exercise regime may have very different needs to a toddler! Then there are environmental factors – in hot weather you will obviously need a higher fluid intake than in cold weather, as your body loses water at a higher rate – this is also true of exercising and illness!

Well, what’s the real figure then?

As you can tell from the previous answer, there just isn’t a cut and dried answer!

The fact is not all your hydration needs are met through drinking glasses of water. While water is the best option for a refreshing drink – tea, coffee, squash and even milk will offer plenty of hydration, but water is caffeine free, additive free, calories free – not to mention cheap! On top of that, you also gain fluid from the foods you eat – typically, fresh fruits have a water content of between 75-95%!

Basically, your aim should be drinking enough that your urine is a healthy clear pale yellow – if its dark, you need to up your fluid intake!

The Eatwell Guide, a basic at a glance nutritional guide produced by the NHS for people over the age of 2 in the UK DOES recommend a fluid intake of 6-8 glasses a day – but that can include a variety of fluids, so it’s important to note that if, like me, you struggle to function without a morning coffee, or you enjoy a smoothie at lunchtime, these count towards your intake! But, as in all things – you should always try to aim for the healthy option, so if you are currently getting most of your daily fluid from coffee and juice, maybe try and cut back on some caffeine and sugar and increase your level of water/healthy options.

The guide also reminds us that you also need to bear in mind that your fluid intake should be higher if you are pregnant or ill, or you have been exercising heavily – or just if it’s a very hot day… you need to replace the fluid lost through sweat!

TLDR?

By all means aim for 6-8 glasses of fluid spread throughout the day, but drink more when you need it, and try and take the healthy options – and remember it isn’t just water that counts towards your total!