Fluid thinking: a guide to hydration

We're encouraged to drink plenty of water, but why? OK, we're mainly water, but beyond that, what does ensuring proper hydration do? Hydration is important to maintain our circulation. It's important for detoxification of the body through, for example, sweating. There is even some evidence that it helps the uptake of fuel into our cells, which may help energy production and metabolism. And it's critical for mental functioning - even mild dehydration has been found in studies to impair our cognitive abilities.

Often, we're advised to drink a specific amount per day (e.g. 2 litres or 8 glasses per day). However, our fluid requirements depend on many different factors, including body weight, ambient temperature, and levels of activity.

Some people defer to 'thirst' as the arbiter of our fluid needs, hence 'drink if you're thirsty'. However, thirst is generally a late sign of dehydration, and this tends to become more pronounced as people age. This is why you may have noticed that elderly people can seemingly go for the whole day on a couple of cups of tea, while in reality they are as dry as a crisp.

So, what works?

A good 'rough and ready' guide to our state of hydration is the colour of our urine. The goal is to drink enough fluid to keep our urine pale yellow throughout the course of the day. I'm not a great wine drinker myself, but think 'Pinot grigio'.

If we find our urine has strayed into darker tones - think Lucozade - and particularly if it's become noticeably odorous, then this is a sure sign that fluid intake is way below par.

Water is a good choice, of course, but some ask if coffee and tea count. They absolutely do. While these may have a mild diuretic effect, this is more than made up for by the water that makes up the bulk of these drinks.

I've found the key factor in whether someone maintains good hydration or not is accessibility: having water (or other beverage) in front of you as you work will usually make the difference.