FOOD FUNDAMENTALS
Water
Hydration
Getting enough water keeps our skin
plump and elastic, helps regulate body
temperature, and ensures our kidneys filter
out waste. If the water concentration in
the blood is too high or too low, the body
compensates by moving water into or out
of our cells; both can be damaging.
Dehydration
If more water is lost than taken in,
symptoms of light-headedness and
tiredness can start within hours. Thirst
is the body trying to correct the problem
before it becomes severe. In extreme
cases, dehydration causes fits, brain
damage, and death.
Water
Up to 60 percent of our body weight is
water and it is needed to keep our organs
functioning. While we can live without food
for several weeks, without
water, death occurs in days,
showing just how important it is.
Decreased attention and memory
If you become dehydrated, brain tissues shrink,
and it takes more effort to carry out simple
tasks. Attention, mood, memory, and reaction
time can be affected, and you may even
become more sensitive to pain.
Low blood pressure
If dehydration is severe, the water content
of your blood falls. Blood becomes thick and
viscous, making it difficult for your heart to
pump it around the body. This can lead to low
blood pressure, dizziness, and fainting.
Dry eyes
Dehydration slows tear
production which can leave
the eyes feeling dry, irritated,
and gritty.
A hydrated brain
Water is vital for the brain to function.
The balance between water and the
substances dissolved in it is important
for neurons to transmit signals effectively.
Blood flows easily
Blood fluid (plasma) is 92 percent
water. The liquid allows oxygen-carrying
red blood cells, infection-fighting white
blood cells, and other vital components
to flow easily to where they are needed.
Moist eyes
To keep the eyes clean
and comfortable, they are
continually moistened with
tears, the major component
of which is water.
CAN YOU DRINK
TOO MUCH WATER?
If you drink too much too
quickly, cells swell as water
rushes in. Swollen brain cells
cause headaches, dizziness,
and confusion. In severe
cases, water poisoning
can lead to death.
DRINKING
WATER
BRAIN
BLOOD VESSEL
E
Y
E
E
Y
E
US_036-037_Water.indd 36 23/02/2017 11:26
36
FOOD FUNDAMENTALS
Water
37
HOW MUCH DO I NEED?
Thirst due to
less water
Sensors in your heart
and arteries respond
when blood volume
falls by 10 percent
or more, and signal
thirst. Drinking tops
up the liquid in your
blood, increasing the
volume of blood.
Thirst due to
high salt intake
The salt concentration
of blood fluid
increases if excess salt
is consumed, causing
water to be drawn
from cells. If salt
concentration rises
by 1 to 2 percent,
thirst is triggered.
Constipation
If you are dehydrated
and food passes through
the large intestine, your
body absorbs water
from it. This leaves
stools dry and hard,
causing constipation.
Concentrated urine
When you are dehydrated, the kidneys reduce the
amount of water excreted, retaining water in the
blood. Urine gets darker in color due to substances
dissolved in the urine becoming more concentrated.
The amount of water you need varies
depending on the climate and what
you spend your time doing. Eight
glasses per day (2–3 quarts/liters) is
frequently advised for moderately
active people in temperate climates,
but this includes fluid from other
drinks and food. For young, healthy
people, the best thing to do is to
listen to your body and drink when
you feel thirsty! However, elderly
people can become dehydrated
without feeling thirsty, and so
must watch their water intake.
Water aids digestion
In your stomach, acidic
liquid, some of which is
water, helps churn and
digest your food. As the
processed food passes
through your intestines,
liquid keeps it moving easily.
Pale urine
When you are well hydrated, your urine
is a pale straw color. If you drink a lot, a
more dilute urine is produced.
Regulating hydration
We lose water mainly through urine,
but some evaporates from the skin, or
is breathed out. The kidneys regulate
water levels in the body and prevent
blood from becoming too concentrated
or dilute. If water levels in your body
tissues or cells fall, thirst is triggered.
INTESTINES
BLADDER
SALTY
SNACK
Water
levels
in cells
don't fall
Water
levels in
cells drops
Fluids outside
cells, such as
blood, drop
in volume
Salt
Water
drawn
out of cell
WATER SOUP JUICE
THE BODY STARTS
TO ABSORB
WATER AS SOON
AS 5 MINUTES
AFTER DRINKING
US_036-037_Water.indd 37 18/01/2017 09:41
36
FOOD FUNDAMENTALS
Water
37
HOW MUCH DO I NEED?
Thirst due to
less water
Sensors in your heart
and arteries respond
when blood volume
falls by 10 percent
or more, and signal
thirst. Drinking tops
up the liquid in your
blood, increasing the
volume of blood.
Thirst due to
high salt intake
The salt concentration
of blood fluid
increases if excess salt
is consumed, causing
water to be drawn
from cells. If salt
concentration rises
by 1 to 2 percent,
thirst is triggered.
Constipation
If you are dehydrated
and food passes through
the large intestine, your
body absorbs water
from it. This leaves
stools dry and hard,
causing constipation.
Concentrated urine
When you are dehydrated, the kidneys reduce the
amount of water excreted, retaining water in the
blood. Urine gets darker in color due to substances
dissolved in the urine becoming more concentrated.
The amount of water you need varies
depending on the climate and what
you spend your time doing. Eight
glasses per day (2–3 quarts/liters) is
frequently advised for moderately
active people in temperate climates,
but this includes fluid from other
drinks and food. For young, healthy
people, the best thing to do is to
listen to your body and drink when
you feel thirsty! However, elderly
people can become dehydrated
without feeling thirsty, and so
must watch their water intake.
Water aids digestion
In your stomach, acidic
liquid, some of which is
water, helps churn and
digest your food. As the
processed food passes
through your intestines,
liquid keeps it moving easily.
Pale urine
When you are well hydrated, your urine
is a pale straw color. If you drink a lot, a
more dilute urine is produced.
Regulating hydration
We lose water mainly through urine,
but some evaporates from the skin, or
is breathed out. The kidneys regulate
water levels in the body and prevent
blood from becoming too concentrated
or dilute. If water levels in your body
tissues or cells fall, thirst is triggered.
INTESTINES
BLADDER
SALTY
SNACK
Water
levels
in cells
don't fall
Water
levels in
cells drops
Fluids outside
cells, such as
blood, drop
in volume
Salt
Water
drawn
out of cell
WATER SOUP JUICE
THE BODY STARTS
TO ABSORB
WATER AS SOON
AS 5 MINUTES
AFTER DRINKING
US_036-037_Water.indd 37 18/01/2017 09:41
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