With summer starting (fingers crossed) to heat up, we need to keep an eye on how much we drink. With children, all that jumping in and out of a pool or the sea and generally dashing around in their holidays can quickly lead to dehydration, which can make them feel unwell, tired and hot, with flushed-looking clammy skin.

In older people, the effects of dehydration were brought into focus a few weeks ago by Baroness Greengross, the founder of the charity Action on Elder Abuse. She explained how in a nursing home in Bury St Edmunds, residents were urged to have between eight and ten drinks a day and, as a result, the number of falls dropped sharply. This is because dehydration also causes dizziness and confusion.

Too little fluid

In general daily life, too little fluid can make you more irritable than usual, with less energy. You can become more forgetful and less able to focus on the task at hand. Children often do not recognise that they are thirsty, and older people often have a reduced sensation of thirst, so we need to be vigilant in helping them to meet their hydration needs. For the rest of us, not drinking enough is often down to habit and not adjusting intakes in hotter weather, and we need to address this ourselves.

What's good to drink?

Although water is an ideal fluid - and, of course, tap water is free - herbal teas, squashes (sugar-free where possible), juices and smoothies also count. You need to watch your calories from the latter two which also, according to dentists, may have negative effects on tooth enamel. Cups of tea count as well, in spite of its reputation as a diuretic. Even coffee and energy drinks with added caffeine have a role in maintaining hydration in spite of the notion that they are a diuretic. However, the general advice for overall health is that we should limit ourselves to about four caffeine-rich drinks daily.

How much should we drink?

Physically active children can lose 350ml-700ml of body fluid in an hour so try to get them to drink about a small yoghurt pot- sized drink (150ml) before going out to play and to have about 100ml every 15-20 minutes. For adults, the most often quoted amount to drink is at least eight 250ml servings a day. If you are worried whether you are getting enough, one simple test is to check the colour of your urine. The paler and more straw-coloured, the better.

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