Water
Water makes up 80% of our bodies and is essential to every imaginable activity and function, from exercise and breathing to fatloss - without sufficient supplies, our bodies simply fail to work properly.
Even an inactive person needs between 4-5 pints (2.5 litres) every day to replace water lost through exhalation, human waste and sweat. In summer, and during exercise, you will need more than this basic amount, which also varies according to the size of your body. Normal tea, coffee and coke contain caffeine, which dehydrates the body - and fruit juices act as a diuretic, increasing the flow of urine. One thing to be aware of is that by the time you are thirsty, you are already partially dehydrated; drinking water or herbal (i.e. non caffeine) teas regularly throughout the day will make sure you are taking in enough liquid.
So how much is lost during exercise?
In extreme conditions sweat loss can temporarily reach in excess of 2 litres per hour although it does not usually exceed around 1 litre p/hr, even in hot conditions. We all know the results of failing to replace these lost fluids – impaired performance, dehydration & cramp; and in severe cases, heat exhaustion.
It is vital, then, to regulate your intake of water dependant on the level of fluid loss – and thirst, as we've explained, should not really be used as an indicator; you should try to avoid it in the first place. However, thirst does act as a warning that something is wrong - although it usually underestimates the level of fluid loss, especially in hot conditions.
This makes it important to take small drinks during exercise - around 250 ml / ½ pint sipped during every 15 minutes should make up for lost fluid. And to ensure re-hydration, this should be maintained after exercise has ceased - even if you do not feel thirsty.
The loss of electrolytes such as potassium, sodium and calcium during exercise (elements that are essential to the function of muscles) also contributes to cramp – around 1.5 grams of salt (sodium) are lost in every litre of sweat.
Although it is very unusual for anyone to have a basic sodium deficiency (everyday meals supply more than enough), sustained perspiration can necessitate some kind of supplement. Nutritious homemade drinks and fruit are an effective and inexpensive way to overcome cramp and dehydration - putting a pinch of salt (providing sodium) in a mixture of water and orange juice (high in potassium) will have the same effect as an expensive commercial sports drink, and without the artificial additives too.
