Although is it not a nutrient, human beings would be unable to survive without it. Over half the human body consists of it and it is essential for the correct functioning of virtually all living cells. For most of us it is as simple as turning on a tap – Water!
Fluids have many functions in the body. They act as a lubricant for joints and eyes, help you swallow, provide the medium in which most reactions in the body occur, act as a cushion for the nervous system and help get rid of waste. On top of that, water helps to regulate body temperature.
But how much do we need? The amount lost (as urine, sweat and in the breath) will vary from person to person because we are all different – it will depend on your age, the time of year, climatic conditions, your diet and how much physical activity you do. Dehydration can be very serious, and 15-20 % of body weight lost as water is fatal. According to a review published in the Journal of the American Dietetic Association, the average man should consume 2.9 litres of water a day and the average women at least 2.2 litres a day. Health professionals recommend at least 1.5 to 2 litres of liquids a day in temperate climates and this includes many other drinks like squash, fruit juices, tea and coffee. The basic point is that you should drink enough to replace what is lost.
- We can obtain our fluid requirements from a number of sources. It is not necessary to only drink ‘pure’ water, although this is a good choice. Like everything else we consume selection depends on personal preference and availability.
- People often forget that some of our fluid requirement comes from the food we eat, not just drinks. Roughly a third of an adult’s daily fluid intake is supplied by what is eaten rather than what is drunk. Fruit and vegetables provide most of this additional fluid but small amounts come from bread and dairy products.
- Although caffeine is a mild diuretic (ie it increases urine output to a small extent) drinks that contain it provide fluids of course. You do not need to drink more water to compensate for consuming these drinks.
- With alcoholic drinks the dehydrating effect can be greater, depending on the type of drink consumed (esp spirits). Remember also the guidelines for safe drinking.
- The sensation of thirst is not triggered until there is already a water deficit so drink before you get thirsty and pay particular attention to children and the elderly who do not recognise the signals of thirst so readily
- Dehydration is common amongst athletes, as little as 2% of body weight lost as water impairs performance. Research has demonstrated that water alone is not the best solution for fluid replacement during or after vigorous exercise. Try isotonic drinks.
- Keep up your fluid levels when you’re on holiday too, e.g. in hot/humid countries.
- Bottled water is recommended where a clean, safe water supply cannot be guaranteed.
- Drinking excessive amounts of water will not lead to better skin, hair and nails.
- Levels of minerals vary in bottled water and ideally minerals should be supplied through a healthy, balanced diet.
© British Nutrition Foundation 2001