Food – a fact of life eSeminar
Healthy Hydration
Laura Wyness and Bridget Benelam,
Senior Nutrition Scientists
British Nutrition Foundation
© 2010 The British Nutrition Foundation
Benelam B and Wyness L (2010)
“Hydration and health: a review”
Nutrition Bulletin 35 (1):3-25.
www.blackwellpublishing.com/nbu
www.nutrition.org.uk/nutritioninthenews/hydration/
© 2010 The British Nutrition Foundation
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Healthy Hydration
Approximately how much of our body is
made up of water?
40%
60%
80%
© 2010 The British Nutrition Foundation
The body contains a large amount of
water
Poor fluid intake can lead to
dehydration.
All drinks count to fluid intake except
stronger alcoholic drinks such as spirits
and wine.
Water is also provided from food
(about 20%).
© 2010 The British Nutrition Foundation
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Why do we need water?
EXCRETION –
get rid of waste
products via
kidneys and
urine production
SALIVA – water
is a key
component in
saliva, helping
us to swallow
JOINTS –
forms
synovial fluid
to keep our
joints mobile
Functions of
Water
REACTIONS –
provides a
medium for all
chemical
reactions in the
body
SWEATING –
for body
temperature
regulation
CEREBROSPIN
AL FLUID – as a
cushion for the
nervous system
TEARS –
forms tears to
lubricate our
eyes
© 2010 The British Nutrition Foundation
Water Balance
• Our bodies have special mechanisms to ensure we stay
hydrated, feeling thirsty is our body’s way of making us
drink more
• The kidneys are very important and help our bodies
maintain water balance by limiting excretion
• Water is lost by sweating, urinating and breathing
• Water is gained by eating and drinking and we produce a
very small amount by metabolism
© 2010 The British Nutrition Foundation
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Dehydration
• Body water volume is tightly controlled and usually
fluctuates by less than 1% per day
• When we are dehydrated we may struggle to focus, feel
tired and get headaches
• If it is hot, you are exercising or you have a high
temperature you may also need to drink more
• Urine should be a pale straw colour. If it is a dark yellow
colour during the day, you might not be getting enough
water
• Due to these mechanisms, serious dehydration is very
rare
© 2010 The British Nutrition Foundation
Can we have too much water?
• Yes
• No
• Don’t know
© 2010 The British Nutrition Foundation
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Over - Hydration
• Drinking too much water is not helpful and in extreme
cases may be dangerous
• Our kidneys usually excrete excess water, but if there is
extreme over-hydration they may not be able to do so
• This can result in low sodium levels in the blood, which
can be very dangerous
• Severe over-hydration is very rare
• If you are frequently urinating and it is very pale, you
may be drinking too much
© 2010 The British Nutrition Foundation
Are you getting enough?
How much should we drink each day?
A) 6-8 glasses of water
B) 6-8 glasses of fluid per day
C) None – we get water fluid from our food
© 2010 The British Nutrition Foundation
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6 – 8 glasses of fluid per day
The amount of fluid we need changes from day to
day, it is affected by many things, including:
• The weather
• Age
• Exercise
But, as a rough guide, try to drink around 6-8
glasses, or 1.2litres per day
This is on top of the water provided by food.
© 2010 The British Nutrition Foundation
How much are we drinking?
• Data on current water consumption in the British
population are not available.
• National Dietary and Nutrition Survey (2000/01)
estimated average fluid intake from drinks:
British men: 1988ml/day
British women: 1585ml/day
© 2010 The British Nutrition Foundation
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Drinks
© 2010 The British Nutrition Foundation
Do Other Drinks Count?
YES!!!
• ‘Fluid’ does not only include water, but water is a great
choice as it delivers fluid without adding calories and
damaging teeth.
• This should be considered when choosing drinks, as the
energy we drink counts towards our calorie intake the
same way food does!
• Sugary and acidic drinks may also cause tooth decay
and erosion
© 2010 The British Nutrition Foundation
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Water
Delivers fluid without adding energy or
potentially damaging teeth.
Does not contribute to energy intake.
Flavoured water may provide energy
depending on sugar content
© 2010 The British Nutrition Foundation
Even Tea and Coffee?
YES!
© 2010 The British Nutrition Foundation
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Tea and Coffee
•
There is lots of confusion regarding tea and coffee affecting your water
intake – with some sources even saying you should drink more water when
you have coffee
•
Moderate amounts of caffeine does not cause dehydration, so tea and
coffee do count towards your fluid intake
•
Other hot drinks, e.g. herbal teas and hot chocolate also count.
•
If these drinks are sweetened with sugar their calorie intake will be
increased and they will be more damaging for teeth
•
Pregnant women are advised to consume no more than 200mg caffeine a
day.
•
This is equivalent to:
2 mugs of instant coffee
or 3 cups of tea.
© 2010 The British Nutrition Foundation
Milk
Provides protein, calcium and B vitamins.
Wholemilk contains saturated fat, it is advisable for adults to
choose lower fat milks: semi-skimmed (2% fat), 1% or
skimmed (less than 0.1% fat).
For children aged 1 - 2 years,
wholemilk is recommended.
From 2+ years,
semi-skimmed milk can be introduced.
1% or skimmed milks are not suitable for children until they
are at least 5 years old.
© 2010 The British Nutrition Foundation
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Fruit Juices & Smoothies
• Provide water, vitamins, minerals and natural plant
substances
• Fruit juices (150ml) count towards one portion of 5 A
DAY.
• Smoothies contain puréed fruit, which adds fibre.
Smoothies (150ml juice and 80g crushed fruit) count as
two portions.
• However, they both contain sugar and acid so can
potentially harm teeth.
© 2010 The British Nutrition Foundation
Soft Drinks
• Are a source of water, but if they contain
sugar this will count towards your calorie
intake and potentially harm your teeth
• It’s a good idea to swap these for low
sugar / diet versions!
© 2010 The British Nutrition Foundation
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What is the most popular drink
in the UK?
Tea ...
Coffee …
Tap water …
Bottle water …
Soft drinks …
Fruit juice …
Alcoholic drinks …
© 2010 The British Nutrition Foundation
What is the most popular drink
in the UK?
Tea ...
536 ml/person/day
Coffee …
744 ml/person/day
Tap water …
333 ml/person/day
Bottle water … 229 ml/person/day
Soft drinks …
211 ml ‘regular’ & 240ml low calorie/person/day
Fruit juice …
106 ml/person/day
Alcoholic drinks … 425 ml/person/day
© 2010 The British Nutrition Foundation
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Alcoholic Drinks
• These do contain water, but the alcohol acts as a diuretic,
increasing the amount of water we lose through urine
• Drinks with a high alcohol content, e.g. wines and spirits
cause diuresis, making you more likely to be dehydrated.
• Normal strength beer, lager and cider cause a net water gain
overall as the alcohol is more dilute
• It is still important to keep alcohol consumption within the
recommended limits
Men - no more than 3-4 units per day.
Women - no more than 2-3 units per day.
© 2010 The British Nutrition Foundation
One unit of alcohol is:
• half a pint of standard strength (3 to 5% ABV)
beer, lager or cider;
• a pub measure of spirit;
• half a glass of wine;
• two thirds of an Alcopop.
© 2010 The British Nutrition Foundation
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Contribution from food
Water is also provided from food (about 20%)
–
–
–
–
–
–
80-90% water in fruit and vegetables
75-80% water in yogurts
65-80% water in rice and pasta
40-50% water in cheese
30-45% water in bread
1-10% water in savoury snacks and confectionary
Foods, such as soups, stews, yogurts have a high
water content.
© 2010 The British Nutrition Foundation
When do we need extra
water?
© 2010 The British Nutrition Foundation
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Some people need to take care to
stay hydrated
• Children
• Pregnant and lactating women
• Older adults
© 2010 The British Nutrition Foundation
Physical activity
Even slight dehydration has been shown to affect
sporting performance, so drink before, during and
after you train or play a match.
The fluid needed for activity is more than the daily
recommendation of 6 to 8 glasses (1.2 litres) each
day.
Being dehydrated may mean that:
•You don’t perform your best
•Your concentration is impaired
•You feel more fatigued
© 2010 The British Nutrition Foundation
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Conclusion
• Water is essential for life
• For the body to efficiently function we need to maintain
optimum hydration
• Water requirements vary from person to person, so
remember your urine should be a pale straw colour
• The body has several mechanisms to control the
balance of water and usually total body water remains
stable.
• Serious dehydration is unlikely in the UK
• Water comes from food and drink
• Beverages also contain calories
© 2010 The British Nutrition Foundation
Healthy hydration resources
www.nutrition.org.uk/nutritioninthenews/hydration/
healthy-hydration-guide
Available in –
Education News
© 2010 The British Nutrition Foundation
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Thanks for listening! For more information visit
www.nutrition.org.uk
www.foodafactoflife.org.uk
Future eSeminars:
• 11.10am - 12.10pm Tuesday 23rd November 2010, Interactions between
physical activity and appetite control: Can we reduce the energy gap?
• 12:30pm - 1:00pm Monday 13th December 2010, Satiety
•1:00pm - 1:30pm Wednesday 19th January 2011, What's your beef? Red
meat in the diet
•12.30pm - 1.00pm Thursday 17th February 2011, Omega 3 Fatty Acids and
Heart Disease - Just another fishy story?
•12:30pm - 1:00pm 16th March 2011, Diet and the immune system
© 2010 The British Nutrition Foundation
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