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Woman with glass of water


Alison Greenhalgh

Although it contains no nutrients, water is a vital component of our diets. It's essential for the growth and maintenance of our bodies, as it's involved in a number of biological processes. But most of us don't get nearly enough.

Why do we need water?

Water comprises 50 to 70 per cent of an adult's total body weight, and without regular top-ups, our body's survival time is limited to a matter of hours or days.

Water is lost from the body through urine and sweat, and must be replaced through our diets. Many people, though, don't consume enough and as a result may become dehydrated, causing symptoms such as headaches, tiredness and loss of concentration. Chronic dehydration can contribute to a number of health problems, such as constipation and kidney stones.

How much do we need?

The body gets its water from three sources:

  • From drinks, either plain water or as part of other beverages.
  • From solid foods, especially fruits and vegetables.
  • As a by-product of chemical reactions within the body.

The British Dietetic Association advises that the average adult should consume 2.5 litres of water per day. Of this, 1.8 litres - the equivalent of six to seven glasses of water per day - must be obtained directly from beverages. This should be increased during periods of hot weather or during and after periods of physical activity.

Water is the major ingredient of all drinks: carbonated and still drinks are 65 per cent water, diluted squashes are 86 per cent water (after dilution) and fruit juices are 90 per cent water. But drinking plain water is still the most effective way of replacing lost fluids.

How to achieve your daily water intake

  • Start as you mean to go on, with a glass of water when you wake.
  • If you're at work, keep a jug of fresh water on your desk so it's within easy reach to top your glass up throughout the day.
  • If you're out and about during the day, carry a bottle of water so you can have a drink whenever you want.
  • Increase your intake of fresh fruit and vegetables; they have a high water content as well as many other health benefits.

Bottled waters

What about bottled waters? There are two types of bottled water: spring water and mineral water. Spring water is collected directly from the spring where it arises from the ground and must be bottled at the source. UK sources of spring water must meet certain hygiene standards, but may be treated in order that they meet limits set on pollution.

Mineral water emerges from under the ground, then flows over rocks before it's collected, resulting in a higher content of various minerals. Unlike spring water, it can't be treated except to remove grit and dirt. Different brands of spring and mineral waters will have differing amounts of minerals depending on their source.

In 1999 Government regulations came into force covering the labelling requirements of bottled waters, to help consumers make informed choices about the products they buy. As a result, the levels of all minerals in natural mineral water must be listed on the label.

But is it necessary to buy bottled water? The drinking water available from our taps is perfectly adequate to replenish our fluid loss, and undergoes many processes to bring it up to the standards set out in the Water Supply Regulations. In 1999, according to Which? Online, 98.8 per cent of tap water sampled passed drinking water inspectorate tests.

There are certainly no proven health benefits of bottled water over tap water - it basically comes down to personal taste and cost.

This article was last medically reviewed by Dr Rob Hicks in September 2005.
First published in March 2001.

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