How much is too much?
Water makes up around 60% of our body weight. We need it to keep our bodies working efficiently. When we are well-hydrated, our blood circulates as it should, our body temperature remains at the right level, and our food is digested properly. We become dehydrated when we lose more water than we take in. Then we become tired, our heads ache, and small tasks seem impossible.
Thus we are advised constantly to make sure we’re drinking enough to remain healthy.
Of course, requirements vary according to body weight
and activity, but official guidelines suggest that women should drink about 2.7
litres a day, and men around 3.7 litres. That includes all sources of fluid, including
plain water, tea, and fruit. Some people worry that tea is a diuretic, and causes
more liquid to be lost than gained, but studies have shown that the loss is minimal,
and tea is an acceptable way to maintain fluid intake.
When high temperatures are forecast the constant advice
is to drink plenty of water and stay well-hydrated.
Is it possible to drink too much water?
Human kidneys can process about one litre of fluid an
hour. Healthy adults should drink enough fluids to make their urine a pale straw-yellow.
It is dangerous to drink more than the kidneys can
cope with. Too much liquid dilutes the blood’s sodium levels. Water then enters
the body’s cells, including those in the brain, causing them to swell. This is
called water intoxication (hyponatremia) and can be fatal.
Mild symptoms of hyponatremia include completely
colourless urine, needing to urinate more frequently – that is, more than nine
or ten times daily, or several times at night – stomach upsets like vomiting, or
diarrhoea, and a persistent throbbing headache.
Serious symptoms indicating a medical emergency include
disorientation, muscle weakness, cramps, seizures, or coma.
If people are expending a lot of energy in intense
exercise, or are living in hot, dry climates and sweating constantly, 4 litres
might be an appropriate amount of liquid.
Athletes in endurance events are the people most at
risk of over-hydrating.
Rather than worrying about the volume of fluid you are
consuming, the best method of ensuring good hydration is to be aware of your
body, and drink when you feel thirsty.