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Most people are familiar with the general recommendation for adults of eight glasses of water a day.
Yet, estimating water or fluid intake requirements is not easy and
individual requirements are highly variable, says Ms Irene Labuschagne,
dietitian and manager of the Nutrition Information Centre (NICUS) at
the Faculty of Health Sciences.
"Water comprises 50% of body weight in women and 60% in men. Every
system and function in the body depends on this fluid. It also aids in
the digestion of food, carries nutrients to cells and provides a moist
environment for ear, nose and throat tissues." However, says Ms
Labuschagne, we also need to realise that the total fluid intake of
humans depends on physical activity levels, the climate they live in,
their health status, clothing and various other physiological factors
such as pregnancy and breastfeeding.
According to Ms Labuschagne, the adequate intake (AI) for total fluid
to prevent dehydration in sedentary men and women (aged 19–50 years) is
3,71 and 2,71 litres of total fluid per day respectively. Solid food
and digestion of food also contributes to this recommendation as food,
such as fruit, also contains fluid.
Drinking fluids represents approximately 81% of total water intake,
which translates into 3,01 litres per day for men (12 glasses of 250
ml) and 2,71 litres per day (10 glasses of 250 ml) for women.
Only water?
Many people prefer alternatives to water such as cool drinks, fruit juices, coffee, tea, milk or sport drinks. However, says
Ms Labuschagne, water is regarded as the preferred drink to fulfil
daily fluid needs. "This is followed by tea, coffee, low-fat and
fat-free milk and drinking yogurts, diet or artificially sweetened cool
drinks, cool drinks or drinks with some nutritional benefits – such as
fruit or vegetable juices, full-cream milk, alcoholic beverages, and
sports drinks – and lastly sweetened drinks or nutrient-poor drinks."
Of this total fluid intake, women should drink at least four glasses
(250 ml) and men at least six glasses (250 ml) of clean, safe water per
day.
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Too much or too little
Although uncommon, it is in fact possible to drink too much water. When
the kidneys are unable to excrete excess water, the electrolyte
(mineral) content of the blood is diluted, resulting in a condition
called hyponatraemia (low sodium levels in the blood). Endurance
athletes such as marathon runners who drink large amounts of water that
do not contain adequate sodium are at higher risk of hyponatraemia.
Hyponatraemia is not a common illness, so don’t go throwing your water bottle away just yet.
Becoming dehydrated is just as dangerous. General signs and symptoms of
dehydration include excessive thirst, fatigue, headache, a dry mouth,
little or no urination, muscle weakness, dizziness and
light-headedness.
As the saying goes, prevention is the best cure. However, if you feel
dehydrated, try to correct it with increased fluid intake. Seek medical
help if you are vomiting or have diarrhoea. "The best options are
rehydration fluid products. Never wait if it is a child. Take the child
to a doctor or health facility," says Ms Labuschagne.
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• Water is highly recommended for daily fluid intake.
It provides no additional energy, which makes it ideal for any
overweight or inactive adult. It also provides variable amounts of
minerals such as calcium, magnesium and fluoride.
• Tea provides antioxidants, flavonoids, amino acids
and minerals (mainly fluoride). Adults should preferably limit their
intake of caffeine drinks to no more than four cups of coffee per day
or eight cups of tea per day. Preferably, these should be with fat-free
or low-fat milk and no sugar.
• Dairy products are by far the richest source of
calcium. There is a positive relationship between milk consumption and
bone-mineral density, which protects against osteoporosis in later
life. Low-fat products are recommended for all adults and children
older than five years.
• Sweetened cool drinks and fruit drinks are energy
dense and contribute to an increased daily energy intake and thus
obesity. Limit these to no more than 240 ml (approximately one standard
cup) per occasion. These drinks should be avoided by diabetics and
inactive, overweight adults and children.
• Fruit juices (100% juice with no added sugar)
provide most of the nutrients of the fruits used, but they are energy
dense and may lack fibre and other nutrients or constituents present in
the whole fruit. Consumption of whole fruits is still considered to be
the best way to achieve satiety and energy balance. Vegetable juices
are generally a healthier alternative to fruit juices because they
provide less energy. However, they can be high in salt. Limit these to
no more than 240 ml (approximately one standard cup) per occasion.
• Sports drinks contain at least half the energy of
sweetened cool drinks and provide sodium, chloride and potassium. The
carbohydrates, water and salts are advantageous in endurance events
(strenuous exercise for more than one hour).
For further or personalised information, contact NICUS on 021 933 1408
or via e-mail at nicus@sun.ac.za or contact a dietician registered with
the Health Professions Council of South Africa. Visit the NICUS website
at www.sun.ac.za/nicu
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