Dehydration - An Explanation, Causes & Prevention
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When the summer sun emerges from behind the clouds to heat up buses & tubes to near sauna temperatures we are bombarded with warnings from the transport authorities to drink plenty of water & avoid dehydration. Wise advice indeed as, apart from oxygen, water is arguably the second most important nutrient our body needs.
What exactly is dehydration & what happens to our bodies when we become dehydrated?
Dehydration, as the name implies, is a shortage of available water in the body. The body uses water for a number of different things including regulation of body temperature through sweating, excretion of toxins and general waste products in urine and faeces and transporting oxygen and other important nutrients around the body via the blood stream (blood plasma is 90% water and plasma accounts for approximately 55% of the volume of your blood).
The body loses water every day through sweating, urination, passing faeces and breathing (it is also worth mentioning that illnesses that cause vomiting and diarrhoea can lead to dehydration as well), so every day we need to replace the lost water to stop ourselves becoming dehydrated.
Sounds pretty logical, but how much water do you need to drink to replace what you lose?
The body produces a small amount of water as a by product of metabolic reactions and is also able to extract water from the food you eat. It is estimated that the shortfall is about 1.5 to 2 litres a day which is where the government recommendation that you need to drink 6 to 8 glasses a day to avoid dehydration comes from. However these calculations are based on the statistical average person and do not take into account any factors that will lead to an increased loss of water. So it stands to reason that if you are involved in any activities that cause you to sweat more (such as trying to keep up with your colleagues during Fighter-Fitness training sessions) then you need to increase your intake of water.
If you know you are going to be doing any form of exercise, or are going to be using the Underground during a heat wave, it is best to hydrate yourself before you go. Drinking small amounts of water at regular intervals before, during and after exercise will give your body the most benefit. Downing two litres of water after running 5 miles puts a lot of pressure on the stomach and kidneys, so is best avoided if at all possible.
So how do you know if you are becoming dehydrated?
Well the most obvious sign is a feeling of thirst, but by the time you are feeling thirsty you are already in the first stages of dehydration. A loss of concentration & dizziness (particularly when standing) can be signs of dehydration as can muscle weakness. Muscles are 75% water so a small decrease in water content can lead to a feeling of muscular weakness. Other symptoms can be constipation and concentrated urine as the body will hold on to the water and not use it to aid excretion. The most extreme cases of dehydration can lead to death.
Finally, it is worth mentioning that although dehydration can have a serious effect on the body, over-hydration can also cause problems. Drinking too much water can place an enormous amount of strain on the kidneys as they have to remove excess water from the body and there are also well documented cases of people who have taken ecstasy and died due to consuming a large amount of water in a very short space of time.
- Author: Stuart Cornock
- Sources: None
