Up to two thirds of the body is water - this equates to 42 litres of
water in a 70kg person! Water is absolutely crucial to the functions
and metabolism of the body and while we can survive several weeks
without food, we would not survive more than a few days without water.
Despite this many of us do not drink enough to maintain an adequate
hydration level. Part of the reason for this is that our thirst
mechanisms are relatively poor and we do not feel thirsty until we are
already considerably dehydrated. Some of the symptoms of dehydration
include headaches, fatigue, low energy, dry mouth and/or bad breath and
a reduced ability to exercise. In fact even a small degree of
dehydration, say 1-2%, results in a decrease in your ability to
exercise. So if, for example, you head to your RPM™ class after work
and haven’t been drinking enough during the day, you will feel more
lethargic than usual and find you cannot push yourself to the same
intensity. Most of the time we put this down to tiredness or what we’ve
eaten, without realizing it’s as simple as being dehydrated.
Fluid balance in your body is determined by:
Water Intake - from food and drinks
Water losses - from urine, faeces, sweat and evaporation from the skin surfaces and lungs
How do I know if I am drinking enough?
It’s
easy to assess your own hydration status simply by noting two things
about your urine – the colour and frequency. Your urine should be very
pale, almost the colour of straw and you should be urinating frequently
throughout the day. Dark-coloured urine and going long periods without
going to the loo are sure signs of inadequate hydration.
How much do I need to drink?
This
is different for everyone and relates to how much fluid you are losing.
Anything which increases the water loss from your body increases your
need to drink. This includes situations that make you sweat more such
as exercise; hot weather; saunas/hot tubs and sickness with a fever or
vomiting and/or diarrhoea. The recommendation is usually to aim for
eight glasses a day. This is very general, however, and the best guide
is to use the urine check as above. If you are a heavy sweater during
exercise try weighing yourself before and after your workout – any loss
is entirely from water loss and you need to drink 1.5litres for every
kg of weight lost. If you lose more than one kg you are not drinking
nearly enough during the workout and this will be affecting your
ability to exercise effectively.
What should I drink?
Without
doubt water is the best option. Water contains no kilojoules and unless
you are exercising for more than 90 minutes there is no need for
anything else. Furthermore since many of us reach for food when we are
in fact thirsty, drinking water regularly throughout the day can help
you to eat less and assist in weight control. Remember that water is
also in many foods such as fruits, vegetables and soups so these also
contribute to your total intake.
Other drinks
Tea and Coffee – these are fine in moderation and in fact have some
benefits including providing antioxidants. They do, however, contain
caffeine and this can upset some people causing symptoms such as
insomnia, heartburn and increased heart rate. Caffeine also has a mild
diuretic effect, although recent evidence shows that this is less than
previously thought, particularly if consumed in moderation. This means
that for each cup of coffee or tea you will lose some of the fluid but
you still benefit from a positive fluid balance. On balance the best
advice is to stick to no more than four cups of tea or coffee a day and
avoid them late at night.
Diet drinks – these provide no energy
but don’t be fooled into thinking they are the same as water. Most
contain significant amounts of caffeine; they are very acidic which
destroys the enamel of your teeth and the sweetness comes from
artificial sweeteners. While there is no strong evidence to suggest
that these additives are harmful, they are ‘artificial’ and cannot be
considered to be part of a natural food diet. By drinking a sweet drink
you are also conditioning your body to like sweet things and there is
some evidence to suggest this makes you crave other sweet things. On
balance one or two won’t do you any harm but if you can choose plain or
sparkling water every time.
Energy drinks – these are usually
advertised with a healthy sporty image and as an energy lift. In fact
they are just glorified soft drinks containing large quantities of
sugar (this is the energy) and caffeine to stimulate the central
nervous system giving you a ‘lift’. Many contain guarana with the claim
that this is a natural product but guarana is just caffeine so there is
no advantage to be gained. Furthermore the amounts of caffeine are
often much higher than in a standard cup of coffee. In short these are
best avoided.
Fruit juice and cordials – these are fine in
moderation but are not the best choice if fat loss is your goal. They
are intermediate energy-dense drinks and can contribute significantly
to your energy intake while not being very filling. You are much better
to consume the whole fruit.
Sports drinks – these are carefully
formulated and invaluable for those involved in high levels of
training. They contain very specific amounts of electrolytes and
carbohydrate for faster absorption than water alone and provide
carbohydrate energy to support prolonged exercise. Unless you are
exercising for more than 90 minutes there is no need for a sports
drink. Consuming them will only add calories and if fat loss is your
goal this is clearly not helpful.
Alcohol – alcohol is not only
energy-dense but also acts as a diuretic increasing your dehydration.
Exercising after you have been drinking is not a good idea and be
mindful that if you head to the gym to ‘sweat out a hangover’ you will
be starting with considerable dehydration and low blood sugars if you
also haven’t eaten. If you really want to work out in this situation, a
sports drink is a good idea and remember to take it easier than you
normally would.
Tips to Ensure a Good Water Intake
Always carry a water bottle with you – keep one in the car, at work and in your gym bag
Fill a large bottle of water in the morning and keep it on your desk or
at home – make sure you have finished it by the end of the day
If you’re not too keen on plain water try adding sliced lemon or mint leaves for extra flavour
Always order a jug of water for the table in restaurants or try sparkling water with a twist of lemon
Drink 500ml of water one hour before exercise; drink at least 100ml
every 10 minutes during exercise and drink a further 500ml after
exercise
Have no more than four cups of tea or coffee a day