Dehydration

At least 75 per cent of us are dehydrated without even realising. We look at why fluid is so vital to us

Water is essential to our bodies and accounts for around 65 per cent of our body weight. Many different parts of the body are made up of water, including blood, which is 95 per cent water, and skin, which is around 70 per cent water. In fact, most organs and bodily functions are dependent on water, which is why H2O is so vital for survival.
Our body is able to regulate how much water it holds, constantly fluctuating between different states of hydration. It uses the kidneys to either excrete excess water as urine, or withhold water – this occurs when you haven’t drunk much water recently and your body needs to retain it for use. In this case, you produce less urine, which is more concentrated. However, if you are not taking in enough fluids through the day, you will become dehydrated.

Working up a thirst
By the time you feel thirsty, or get a dry mouth, you’re already dehydrated. You may find you lose concentration or feel less alert. This is because the brain, which monitors those activities, is about 75 per cent water, so a lack of it will reduce its ability to function (so that’s why your head feels fuzzy after over-indulging in alcohol).
It’s actually not that easy to measure the hydration levels in your body. However, a good indicator of whether you’re dehydrated or not is by looking at the colour of your urine (see right). You should be aiming for a pale yellow straw-like colour. If it’s dark yellow or brown, then you are most likely dehydrated and should take action straightaway.
If you fail to drink water at this stage, you may experience other symptoms such as headaches, dry eyes, light-headedness and bad breath caused by less saliva in the mouth. If you’re repeatedly dehydrated, long-term ailments could include constipation, as stools in the bowel become hard and dry, and difficult to excrete. Dehydration can affect your kidney function, and lead to kidney stones – caused by salts and minerals forming and creating crystals – and you may find you get more urinary tract infections, as you lack adequate fluids to flush out bacteria in the bladder. Finally, your skin could become drier, meaning it appears thicker and more wrinkled.

Key causes
While not drinking enough fluids can put you at risk of becoming dehydrated, there are other factors that may worsen the situation.
Activity Doing lots of exercise means your body will be sweating out fluid. If this fluid is not replaced before, during or after exercise, you will become dehydrated.
Temperature If you’re in an especially hot environment, such as on the beach, you’re more at risk of dehydration because of increased sweating.
Tummy troubles If you’re unlucky enough to be struck down with vomiting or diarrhoea, you could become dehydrated, as it’s harder to keep liquids down.
Illness Anyone running a high temperature due to fever should be mindful of their hydration levels.
Diabetes can increase your risk of dehydration. In diabetes, glucose leaks into your urine and ‘pulls out’ extra water through the kidneys. This can make you thirsty, and cause you go to the toilet more.

Who’s at risk?
The two main groups who need to ensure they’re drinking plenty of fluids are children and babies, and the elderly. Young children are less effective at regulating their temperature, and have a larger surface-to-weight ratio than adults. Their low body weight makes them more vulnerable to the effects of fluid loss, so they are more likely to get dehydrated. Even mild dehydration can cause symptoms such as confusion, irritability and tiredness.
Older people are more at risk of dehydration because they may have incontinence issues and mobility problems, meaning they may choose to drink less to avoid going to the loo. Plus a person’s sense of thirst becomes less acute with age. A dehydrated older person could become confused, light-headed and at risk of hospitalisation.
If you or a family member does become dehydrated, obviously, the first step is to drink some fluids. Those who have vomiting or diarrhoea may benefit from using some electrolyte sachets, containing salts and sugars, as it will speed up your recovery from the illness as well as aid rehydration.
In cases of severe or clinical dehydration, you will need to go to hospital. The body systems will start to shut down including cognitive function, so you may become dizzy and disorientated. This also affects the exchange of oxygen within the lungs so that the lung lining starts to dry out and breathing will become difficult. Medical staff will insert an intravenous drip to get fluids inside your body as quickly as possible.

Staying hydrated
It is important that you keep your fluid levels up throughout the day, and that they are maintained evenly. Our fluid requirements are individual and depend on factors such as body weight, size, physical activity and the temperature of our environment. However, the average adult needs about 1-2 litres of fluid a day, which is about eight glasses – more if you’re exercising or are in a hot environment. Try to avoid ‘camel syndrome’ – where you take on massive amounts of fluid and then drink nothing for several hours – aim for roughly half a tumbler glass of water each hour. The kidneys function better when they have a steady input and output of liquid.
Don’t forget, you can include other liquids such as tea, coffee and juices to up your quota. While it is true that caffeine is a diuretic, in reality, drinking caffeinated drinks only has a negative effect on your fluid levels if you are not used to them. So drinking five cups of tea won’t have much of a diuretic effect if this is usual for you. However, if you have the occasional cup, you could find it leaves you feeling thirsty afterwards.
Other ways to increase your fluid intake include herbal teas, fruit juices and smoothies (although watch how many of these you give to children as the acids in them could affect their tooth enamel), and diluted squash. Foods can also add to your fluid quota – see below for more on this.

Top hydration tips
1 Make sure you always have access to water – even when out and about .
2 Drink water at regular intervals throughout the day.
3 Start the day with a glass of water before enjoying other drinks –  this is the best way to rehydrate yourself.
4 Remember that water-containing foods – such as fruit and raw vegetables, soup and milk or yogurt – contribute to daily fluid intake.
5 Alcohol is dehydrating and should be balanced out with plenty of non-alcoholic drinks, such as water.
6 Remember to drink more when you exercise or spend time in hot environments.

Did you know?
When you exercise, not only are you losing fluid, you’re also losing electrolytes – natural salts such as sodium and potassium. If you fail to keep your electrolyte level up, you could be at risk of cramps. Try sipping isotonic drinks while you exercise.

Expert: Dr Paul Stillman
A GP in Sussex, Dr Stillman is also a member of the Expert Group in Hydration, a think tank set up to provide comment about the role of hydration for good health