TYPES OF FOOD
Sugar highs and lows
Sugar highs and lows
Every cell in our body needs the sugar glucose for energy, and many
different types of food can be broken down to provide this glucose.
Eating a balanced diet gives us a steady supply, but sugary snacks
can send blood sugar levels swinging wildly.
Sugar highs and lows
Every cell in our body needs the sugar glucose for energy, and many
different types of food can be broken down to provide this glucose.
Eating a balanced diet gives us a steady supply, but sugary snacks
can send blood sugar levels swinging wildly.
Regulating blood sugar
Our bodies function best when blood glucose levels are
within a certain range. If levels increase too much, the
pancreas releases insulin, encouraging fat and muscle
cells to absorb glucose. Glucose not needed by cells
immediately for energy is stored in the liver as
glycogen or as fat in cells around the body. If blood
glucose falls too low, another pancreatic hormone
(glucagon) stimulates the liver to convert glycogen
back into glucose. If this isn’t enough, fat stores are
used. In diabetes, cells don’t produce or respond to
insulin properly, so blood sugar levels can fluctuate
greatly, producing various symptoms (see pp.216–17).
Body maintains blood
glucose within a normal
range when provided
with a balanced diet
Riding a roller coaster
When we eat lots of sugary snacks, our body
struggles to keep up, leading to a cycle of rising
and falling blood sugar. Over years, this can
cause a decrease in our sensitivity to insulin,
leading to type 2 diabetes.
B
L
O
O
D
S
U
G
A
R
L
E
V
E
L
Contrary to popular belief, children
don’t become hyperactive after
eating sugary treats. Studies have
shown that, rather than the
child’s actual behavior, it is
the parents’ perception of
their child’s behavior that
changes after they are told
their child has eaten sugar.
HYPERACTIVE KIDS?
The sugary snack pushes
blood glucose above normal
levels as glucose floods into
the bloodstream
Sugary snack
Blood sugar falls to the
bottom of its normal range,
which may stimulate us to
eat a sugary snack
SUGAR HIGH
SUGAR LOW
IS SUGAR
ADDICTIVE?
Sugar cravings are common,
and there is evidence that
some people may develop a
psychological dependence on
sugar. Whether it is physically
addictive in the same way
as alcohol is uncertain.
US_140-141_Sugar_highs_lows.indd 140 18/01/2017 09:45
140
TYPES OF FOOD
Sugar highs and lows
141
SUGAR LOW
Food and blood sugar levels
To give an accurate idea of how different
foods affect blood sugar levels, scientists have
devised two measures, the glycemic index (GI)
and glycemic load (GL). The GI of a food is a
measure of how quickly it raises your blood sugar
level (see p.91). However, it does not tell you the
total amount of carbohydrate and so gives no
indication of how high your blood sugar level
could rise. The GL is designed to give a more
accurate picture by taking into account both the
GI of a food and the total amount of carbohydrate
in the serving. In general, a GL of 10 or less is
considered to be low, while 20 or more is high.
Glycemic index vs. glycemic load
Foods with a low GI may have a high GL, and vice versa. For
example, watermelon has a high GI but, for a typical serving
(4.2oz/120g), a low GL; chocolate cake has a relatively low GI,
despite being a sweet food, but a much higher GL than
watermelon for the same serving size of (4.2oz/120g).
B
L
O
O
D
S
U
G
A
R
L
E
V
E
L
EXTREME RANGE
Blood sugar rises
beyond normal
range again
More sugary
snacks
Blood glucose falls to the bottom of its normal range
again. Despite many people reporting a “sugar crash,” this
is psychological and blood glucose levels do not plunge
lower than normal in healthy people
More insulin produced and
more sugar deposited as
glycogen or fat
Excess glucose prompts
production of insulin,
which results in a rapid
fall in blood sugar as
glucose is taken up by
muscle and fat cells and
converted into glycogen
or fat deposits
SUGAR HIGH
SUGAR LOW
NORMAL RANGE
100
GI GL
72
22
38
WATERMELON
WATERMELON
CHOCOLATE
CAKE
CHOCOLATE
CAKE
0 0
4
25
MINUTES
THE TIME IT TAKES FOR
BLOOD SUGAR TO
PEAK AFTER EATING
A SUGARY SNACK
20
US_140-141_Sugar_highs_lows.indd 141 23/02/2017 14:40
140
TYPES OF FOOD
Sugar highs and lows
141
SUGAR LOW
Food and blood sugar levels
To give an accurate idea of how different
foods affect blood sugar levels, scientists have
devised two measures, the glycemic index (GI)
and glycemic load (GL). The GI of a food is a
measure of how quickly it raises your blood sugar
level (see p.91). However, it does not tell you the
total amount of carbohydrate and so gives no
indication of how high your blood sugar level
could rise. The GL is designed to give a more
accurate picture by taking into account both the
GI of a food and the total amount of carbohydrate
in the serving. In general, a GL of 10 or less is
considered to be low, while 20 or more is high.
Glycemic index vs. glycemic load
Foods with a low GI may have a high GL, and vice versa. For
example, watermelon has a high GI but, for a typical serving
(4.2oz/120g), a low GL; chocolate cake has a relatively low GI,
despite being a sweet food, but a much higher GL than
watermelon for the same serving size of (4.2oz/120g).
B
L
O
O
D
S
U
G
A
R
L
E
V
E
L
EXTREME RANGE
Blood sugar rises
beyond normal
range again
More sugary
snacks
Blood glucose falls to the bottom of its normal range
again. Despite many people reporting a “sugar crash,” this
is psychological and blood glucose levels do not plunge
lower than normal in healthy people
More insulin produced and
more sugar deposited as
glycogen or fat
Excess glucose prompts
production of insulin,
which results in a rapid
fall in blood sugar as
glucose is taken up by
muscle and fat cells and
converted into glycogen
or fat deposits
SUGAR HIGH
SUGAR LOW
NORMAL RANGE
100
GI GL
72
22
38
WATERMELON
WATERMELON
CHOCOLATE
CAKE
CHOCOLATE
CAKE
0 0
4
25
MINUTES
THE TIME IT TAKES FOR
BLOOD SUGAR TO
PEAK AFTER EATING
A SUGARY SNACK
20
US_140-141_Sugar_highs_lows.indd 141 23/02/2017 14:40
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