Water is an essential part of the diet. Humans are able to survive for several weeks without food, but for only a few days without water.

Since the body has no means of storing water, you need a constant supply to replenish the fluid that you lose through sweating and urination. This means that you need to drink at least six to eight glasses of water every day, and more when it is hot or when playing sport or taking exercise. Do not wait until you are thirsty, since thirst may indicate that you are already lacking the water you need (see The Need for Fluids).
Limit fizzy drinks and juice

In the UK, the consumption of fizzy drinks has doubled in the past 15 years - on average, we now drink over 2 litres (3 ½ pints) of sugary fizzy drinks, squash, and fruit juice per person every week. Although these sorts of drinks provide fluid, they also contribute a large amount of calories and sugars to the diet. The marked increase in the consumption of sugary fizzy drinks and juice is believed to be a major factor in the rising number of overweight children in Britain.
Making changes in your drinking habits

You can save hundreds of calories each day by paying attention to what you drink during the day, and by trying to substitute still or sparkling water, or other low-calorie drinks, for those with a high sugar content.

If you make only one dietary change after reading this guide, drinking water rather than cola may be the most realistic and effective one that you can do. If you currently have a juice drink with lunch and a sugary fizzy drink with snacks, wean yourself off these gradually: substitute water for lunch for about a week, then slowly, over time, introduce more water or diet drinks. Try a glass of skimmed milk with snacks, to boost your fluid levels and also your calcium intake.

We are constantly being urged to drink six to eight glasses of water each day for better health. For many years, it was believed that caffeinated beverages did not count towards this fluid intake because they have a dehydrating effect. However, studies have found there was no evidence to substantiate this belief, so beverages such as coffee and tea, which consist mainly of water, can count towards your daily fluid needs.

Adequate fluid intake is vital for everyone, but especially for the elderly, who are prone to dehydration because of a decline in their thirst sensation.