NUTRITIONAL DISORDERS
N
ESSENTIAL NUTRIENTS
Proteins
The main structural component
oftissues and organs. We need
proteins for growth and repair
of cells. Each protein contains
hundreds and sometimes
thousands of units called amino
acids in specific combinations.
In the body there are
20
different
amino acids;
12
ofthese can be
manufactured by the body itself
and the remaining eight can only
be obtained by eating a balanced
diet. A vegetarian diet that contains
eggs, milk, and cheese provides
sufficient amounts of all the
essential amino acids. A vegan diet,
which also excludes dairy products,
needs careful planning in order to
prevent a deficient intake of protein
(see
Vegetarianism).
Carbohydrates
The two carbohydrate food groups,
sugars (simple carbohydrates) and
starches (complex carbohydrates),
are the main energy sources that
are required for metabolism
(chemical processes that take
place in cells).
Complex carbohydrates should
make up at least half of the diet.
Complex carbohydrates found in
cereals and fruit are rich in fibre and
nutrients. Refined carbohydrates
such as sugar and white flour
should be keptto a minimum.
Fats
Fats provide energy for metabolism
and are a structural component of
cells. Most people in developed
countries eat too much fat; fats
should constitute no more than
30
per centoftotal calorie intake.
There are three types of dietary fats:
saturated fats (found mostly
in meat and dairy products),
monounsaturated fats (found in
olive oil and avocados), and
polyunsaturated fats (found in fish
and vegetable oils). Saturated fats
tend to increase the amounts of
unwanted types of cholesterol in
the blood whereas polyunsaturated
fats and monounsaturated fats have
the opposite effect. Studies have
indicated thata high level of low-
density lipoprotein cholesterol
in the blood is associated with
coronary artery disease. Our
bodies naturally produce enough
cholesterol for our needs; excess
is mostly due to eating too much
saturated fat.
Fibre
This is the indigestible structural
material that is found in plants.
Although fibre passes through the
intestine unchanged, it is an
essential part of a healthydiet.
A diet low in fibre may lead to
constipation, diverticular disease,
and other disorders.
High-fibre diets (including plenty of
fruit, raw vegetables, grains and
cereals) provide bulkwithout excess
calories. Low-fibre diets tend to be
high in refined carbohydrates and
fats, and thus increase the risk of
developing obesity, heart disease,
and some cancers.
Water
Our bodies are composed of about
60
per cent water. Water constitutes
a high proportion ofmany foods,
particularly fruit and vegetables,
and is essential to maintain
metabolism (chemical processes
in cells) and normal kidney and
bowel function. Water is also the
major component of the volume
of blood in the circulation.
Vitamins
Regulators of metabolism. Vitamins
ensure the healthy functioning of
the brain, nerves, muscles, skin,
and bones. Although vitamins do
not supply energy, some enable
energy to be released from the food.
A healthy, balanced diet contains
enough vitamins for most people’s
needs, and supplements are not
usually necessary. Indeed, some
vitamins that are stored in fats
(A
, D
. E. and K) are dangerous if
taken in excess. The body can store
only relatively small amounts of
water-soluble vitamins (B and C),
but even on a very restricted diet,
vitamin deficiency is rare until
several months have elapsed.
Minerals
A balanced diet provides enough
minerals for most people. Calcium
is necessary for the maintenance of
healthy teeth and bones. Other
minerals, such as zinc and
magnesium, are needed in minute
amounts to control cell metabolism.
The only mineral commonly
required as a supplement is iron,
which is used to prevent anaemia
in women who have heavy periods.
Sodium chloride (salt) is needed to
maintain fluid balance; excess may
cause high blood pressure.
a n d o n t h e l e v e l o f p h y s i c a l a c t i v i t y . T h e
r a t e a t w h i c h t h e b o d y u s e s e n e r g y s i m -
p l y t o m a i n t a i n b a s i c p r o c e s s e s s u c h a s
b r e a t h i n g
a n d
d i g e s t i o n
i s
c a l l e d
t h e
b a s a l m e t a b o l i c r a t e
( B M R ) . E x t r a c a l o -
r i e s a r e n e e d e d f o r
a l l o t h e r
a c t i v i t i e s ;
e n e r g e t i c s p o r t s i n c r e a s e c a l o r i e r e q u i r e -
m e n t . E n e r g y r e q u i r e m e n t s a l s o d e p e n d
o n
g e n d e r
( f o r
e x a m p l e ,
a n
a v e r a g e
w o m a n r e q u i r e s a b o u t 2 , 0 0 0 k c a l d a i l y ,
c o m p a r e d w i t h a b o u t 2 , 5 0 0 k c a l f o r a n
a v e r a g e
m a n )
a n d
a g e
( a
g r o w i n g
t e e n a g e r r e q u i r e s m o r e c a l o r i e s t h a n a n
a d u l t a n d t h e B M R d e c l i n e s w i t h i n c r e a s -
i n g a g e ) . A p r e g n a n t w o m a n n e e d s m o r e
c a l o r i e s t h a n a n o n p r e g n a n t w o m a n .
I f m o r e c a l o r i e s a r e c o n s u m e d t h a n a r e
n e e d e d , t h e e x c e s s e n e r g y i s s t o r e d a s f a t
a n d w e i g h t i s g a i n e d . W e i g h t l o s s o c c u r s i f
d e m a n d s f o r e n e r g y e x c e e d c a l o r i e i n t a k e .
( S e e a l s o
e n e r g y r e q u i r e m e n t s
;
m e t a b o l i s m
.)
n u tritio n a l d is o rd e rs
N u t r i t i o n a l d i s o r d e r s m a y b e c a u s e d b y
a d e f i c i e n c y o r e x c e s s o f o n e o r m o r e
n u t r i e n t s
,
o r b y t h e p r e s e n c e o f a
t o x i n
( p o i s o n o u s e l e m e n t ) i n t h e d i e t .
NUTRITIONAL DEFICIENCY
A d i e t d e f i c i e n t i n
c a r b o h y d r a t e s
i s u s u a l l y
a l s o d e f i c i e n t i n
p r o t e i n
,
l e a d i n g t o p r o -
t e i n - c a l o r i e m a l n u t r i t i o n , w h i c h m o s t
o f t e n o c c u r s a s a r e s u l t o f s e v e r e p o v e r t y
a n d f a m i n e ( s e e
k w a s h i o r k o r ; m a r a s m u s
) .
I n a d e q u a t e i n t a k e o f p r o t e i n a n d c a l -
o r i e s
m a y
a l s o
o c c u r
i n
p e o p l e
w h o
r e s t r i c t
t h e i r
d i e t
e x c e s s i v e l y
t o
l o s e
w e i g h t ( s e e
a n o r e x i a n e r v o s a
) ,
h o l d m
i s -
t a k e n b e l i e f s a b o u t d i e t a n d h e a l t h ( s e e
f o o d f a d
) ,
o r l o s e i n t e r e s t i n f o o d d u e t o
a l c o h o l d e p e n d e n c e
o r
d r u g d e p e n d e n c e
.
D e f i c i e n c y
o f
s p e c i f i c
n u t r i e n t s
i s
c o m m o n l y a s s o c i a t e d w i t h a d i s o r d e r o f
t h e d i g e s t i v e s y s t e m , s u c h a s
c o e l i a c d i s -
e a s e ,
C r o h n ’s
d i s e a s e ,
o r
p e r n i c i o u s
a n a e m i a ( s e e
a n a e m i a , m e g a l o b l a s t i c
) .
NUTRITIONAL EXCESS
O b e s i t y
r e s u l t s
f r o m
t a k i n g
i n
m o r e
e n e r g y
f r o m t h e d i e t t h a n i s u s e d u p b y
t h e b o d y . I t i s a m
a j o r t h r e a t t o h e a l t h
a n d i s a s s o c i a t e d w i t h d i s o r d e r s s u c h a s
c o r o n a r y a r t e r y d i s e a s e
,
h y p e r t e n s i o n
( h i g h
b l o o d p r e s s u r e ) , a n d
s t r o k e
( d a m a g e t o
p a r t o f t h e b r a i n d u e t o i n t e r r u p t i o n t o
i t s b l o o d s u p p l y ) . A n e x c e s s i v e i n t a k e o f
s a t u r a t e d f a t i s t h o u g h t t o b e a f a c t o r i n
c a r d i o v a s c u l a r d i s e a s e a n d i n c e r t a i n
c a n -
c e r s
.
N u t r i t i o n a l d i s o r d e r s m a y a l s o r e s u l t
f r o m e x c e s s i v e
m i n e r a l s
a n d
v i t a m i n s
.
TOXINS
N a t u r a l l y o c c u r r i n g t o x i n s c a n i n t e r f e r e
w i t h t h e d i g e s t i o n , a b s o r p t i o n , a n d / o r
u t i l i z a t i o n o f n u t r i e n t s o r c a u s e s p e c i f i c
554
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