Water is essential for life. The body is roughly two- thirds water and this fluid performs many functions including the transport of nutrients, maintaining blood volume, removing waste products via urine and aiding movement of waste through the bowel, as well as acting as a lubricant and shock absorber in joints. It also regulates the body’s temperature. Looking at that list of jobs, it’s easy to see why drinking enough water is vital to maintain good health in the short and long term – for example, the prevention of constipation, kidney stones and urinary tract infections. Good hydration can also prevent other conditions such as chronic renal disease.

Dehydration happens when you don’t replace the fluids lost through urine, sweat and breathing. The most obvious symptom is thirst but it’s not the only one or even necessarily the first. A headache, a lack of concentration, lethargy and mood swings are not commonly recognised as such but they are all marks of dehydration. Both fine and gross motor skills are also affected, although you may not necessarily notice impairment in your motor skills (unless you are trying to thread a needle for example!). Dehydration is very common, and not everyone is aware of how it can affect the way we feel and our energy levels. If you ever find yourself lacking in energy and reaching for a sugar hit then read on.

Mid-afternoon is when a lot of people seem at their most vulnerable to this sweet-snacking behaviour, but this can be counterproductive as it may well cause a spike in blood sugar, which is then followed by a crash. When that afternoon lull happens just having a drink of water can perk you up no end – without the calorie input and sugar crash.

So what drinks are good for rehydration? Water and anything that contains it will generally rehydrate, so if you don’t like water but will happily drink tea or squash – particularly if it has no added sugar – that is all good. Coffee also counts as do fizzy drinks, but do think about sugar content and remember that too much caffeine may impair your sleep.

The European Food Safety Authority recommendation for adequate intakes of fluid per day is two litres for women and 2.5 for men.10 There are all sorts of things that affect hydration levels though. For example, sweating is a mechanism to cool the body. So if it is a hot day and you sweat a lot you will find that you are losing a significant amount of fluid, which will need to be replaced.

Short of measuring the amount of fluid you eat, drink and excrete, there is another way to gauge your hydration level. There are systems in your body that hold on to water if you are dehydrated and that means that urine volume goes down. However, you still need to rid your body of all those waste products, which leaves urine looking darker. So, the colour of your urine is a very good indicator of your hydration status. It should be a pale straw colour, so if it’s darker than that you need to top up!