Enjoy the sun but don't forget to top up on your water intake

Although our bodies are made up of around 70 per cent water and hydration is vital for optimum health, research suggests few people give any priority to how much they drink,

The World Health Organisation recommends a daily fluid intake from drinks and food of 2.2 litres for women and 2.9 litres for men (between around three and four pints).

That may sound a lot, but about 20 per cent comes from the food we eat, and the remainder doesn't have to come from drinking tap water alone. Fluid regulates body temperature and makes up around 80 per cent of blood and 75 per cent of the brain. If we get dehydrated, even by a small amount, it can lead to

a multitude of problems ranging from fatigue, poor concentration, headaches and dry skin, to kidney problems and some cancers.

"When you become thirsty, you're already insufficiently hydrated," says Prof Ivan Tack, a kidney specialist, who spoke at the recent Hydration for Health (H4H) conference in France. "Your mood becomes less stable and intellectual, and physical performance decreases, even with a small amount of dehydration.

"At this point, people are increasing the risk of urine crystallisation, which may be linked to the formation of painful kidney stones. Really, you need to drink before you start feeling thirsty."

Those jetting off to hot countries need to bear in mind that the body excretes water through urine, sweating and breathing. So once body temperature rises, during exercise or in hot weather, you lose more fluid and need to replace it.

While studies have suggested that dehydration can increase the risk of serious problems, including bladder and colon cancer, there is still a dearth of reliable data about the effects of a lack of water in the body.

"We need to discover the medium-term impact of not drinking sufficiently," stresses Prof Tack. "What we do know is adding a little bit of water will optimise your mental and physical performance and while there's no problem

with a little tea or coffee – preferably without sugar – they should be drunk in moderation."

Reducing or eliminating sugar and sweetness in fluid intake is crucial, agrees Dr David Haslam, a GP who is also chairman of the National Obesity Forum. "I've seen parents who think they're doing a wonderful job by giving their children glass after glass of fresh orange juice or carbonated drinks, but that's the key to their weight problems. With a simple switch from too many fruit juices to adding water instead, you can see these kids losing weight."

A good way of checking that you're drinking enough is by checking the colour of your urine – if it's dark yellow, you need to drink more, and aim for it to be much paler, straw-coloured or clear.

"Almost always, people don't drink enough – it's just not seen as a priority," says Dr Haslam. "You've got to be a little bit organised and hydrate. Get into the habit, and drink when the opportunity's there, when there's a tap or a glass or a bottle of water available."