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Water – too much of a good thing?
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8 glasses a day?
Most of us have grown up with the idea that ideally we should drink 8 eight-ounce glasses (approximately 1 ¾ litres) of water a day. But outside of the field of sports medicine it is almost impossible to find good evidence to back up such claims.
Few of us are training for the triathlon (endurance sports are probably the only place where over-consumption of water, for instance drinking up to a litre of water prior to extreme exertion, may be justified) and information about how much fluid sedentary to moderately active individuals need less clear cut.
In most countries, guidelines set by the International Sports Medicine Institute in the US have been adopted as ‘sensible’, even for non-sportspeople: 2/3 ounce of water per pound of body weight daily for an active person and ½ ounce per pound of body weight daily for a sedentary person.
This means that an active person weighing 10 ½ stone needs 2.75 litres (5 ½ pints) of water daily and a sedentary person at the same weight needs 2 litres (3 ¾ pints). And although super thin supermodels may boast that they get through a two litre bottle each day, by these guidelines an eight stone woman is only likely to need 1.5 litres (just over 3 pints) of fluids each day.
However, in the same way that adequate nutrition has little to do with how many vitamin pills you take, adequate hydration is not just a matter of drinking lots of water.
Instead, it is a matter of checks and balances. How much you will need depends on things such as your level of activity, what kind of foods you regularly consume and even the climate you live in.
We each need around 2 litres a day to stay optimally hydrated. More than that, say three litres a day, especially in a cold climate, is simply unnecessary. It is estimated that each day the body loses approximately 1.5 litres of water through sweating, breathing and urinating. This must be replaced.
But the good news is that your daily fluid supply doesn’t all have to come from a bottle or a glass. Fruits and vegetables supply water in a form which is very easy for the body to use, while at the same time providing the body with a high percentage of vitamins and minerals.
Also on the plus side we release about 1/3 of a litre of water into our systems each day when we burn glycogen for energy. When the body digests carbohydrates, they are broken down into glucose – used to meet immediate energy needs – and glycogen.
Glycogen is stored in the muscles and liver for future use. Each molecule of glycogen holds on to 9 molecules of water which is released during the course of your day and at times when you need it most, like during intense exercise.