Your body continually loses water through urine and faeces, through your skin, and from your lungs when you breathe out. So you need to top up your water levels regularly by drinking enough to replace what's lost.
Without perspiration, the normal daily turnover of water in adults is about four percent of body weight, which is 2.8L for a 70kg person. However, the amount of fluid lost will vary from person to person because we're all different - it will depend on your metabolism, your state of health, your diet and how much exercise you do.
According to the Ministry of Health, the average man needs about 3L of water each day; for women it's about 2.2L. Allowing that about one third comes from food, dietitians recommend the average adult drinks at least eight glasses (2L) of fluid per day - more during hot weather and physical activity.
You don't need to drink glass after glass of plain water. There are several other sources of water in your diet. But plenty of water is recommended. Apart from anything else, it's best for quenching your thirst, is cheap (or free) and contains no kilojoules.
Drink more water if any of the following applies:
- You're exposed to high temperatures.
- You're carrying out strenuous work or physical activity.
- You're exposed to air conditioning or heating for long stints.
- You're pregnant or breastfeeding.
- You've got a fever or diarrhoea, or have been vomiting.
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