TEENS - The Basic Food Groups
ratio of food which supply our daily needs should
reflect the groups in the food pyramid. A balanced
diet will include six daily servings of complex
carbohydrates; five servings of fruit or vegetables;
two servings of milk; two servings of protein;
and 15 – 25 gm of fats and oils”.
human body is made up of millions of molecules,
water being the most abundant component. We
need a constant flow of food and its nutrients
to maintain life and promote cell, organ and
tissue growth. Food also provides us with energy,
required for every thought and action that we
perform all day.
fats and carbohydrates are “macronutrients”,
required in large quantities. Minerals and vitamins
are “micronutrients” and although
crucial to our health, only small quantities
previous decades, starchy carbohydrates such
as bread ,pasta, potatoes and rise were considered
to be fattening, stodgy and generally unimportant
foods. The modern view is, that they are an
essential and vital part of a balanced diet.”
are made by plants from sunlight and are our
main source of energy. One gram of carbohydrate
releases four calories of energy.
Carbohydrates are classified into the following
Sugars, based on
their structure, are divided into two groups,
namely the ‘monosaccharides’ and
monosaccharides consist of:
(the principle sugar used for energy purposes)
- fructose (found
in fruit and referred to as ‘fruit sugar’)
(derived when the sugar molecule lactose is
disaccharides consist of:
(milk sugar, and the only sugar of animal
- sucrose (also
called ‘white sugar’ or ‘table
- maltose (malt
sugar found in beer and breakfast cereals).
called ‘polysaccharides’) are composed
of long chains of glucose. Like some types of
sugars, starches require special enzymes to
separate the individual glucose molecules from
one another, before they can be utilized as
an energy source.
Fibre is more complex
in structure than sugars and starch, and humans,
unlike rodents and herbivores, lack the required
enzymes for its digestion. A large proportion
of fibre therefore passes through our gut, mostly
undigested, but aids with the very important
function of elimination.
are two types of fibre naturally found in foods.
fibres (cellulose, hemicellulose) are found
mainly in unrefined grains (digestive bran,
whole wheat flour, brown rice, wholegrain breakfast
cereals) and also in some fruit and vegetables
(cabbage, peas, beans, apple skins.) This kind
of fibre is not so readily broken down in the
bowel by bacteria, and increases the bulk and
water content of stool, thereby stimulating
natural bowel movements.
fibres (pectins, gums, mucilages) are found
mainly in fruit and vegetables (apples, citrus
fruit, strawberries, sweet corn, broccoli, dried
fruit, pears), and in grains, legumes and nuts
(oat-bran, oats, peas, lentils, beans, peanuts,
almonds.) This kind of fibre is rapidly broken
down by bacteria in the bowel. The additional
benefit of consuming soluble fibre is that it
delays stomach emptying, thereby promoting satiety
(feeling of fullness). It also slows the absorption
of glucose from the small intestine, preventing
a surge in insulin levels, resulting in better
Glycaemic control. Soluble fibre is also responsible
for lowering blood cholesterol levels, and is
therefore beneficial in preventing heart disease.
the principle source of energy, glucose
requires special attention.
a meal, all excess glucose molecules not required
for immediate energy purposes are bonded together
via a chemical process into one long chainlike
molecule called ‘glycogen’. Glycogen,
in turn, is stored in two ‘pantries’
in the body, namely the liver and the muscles.
These ‘pantries’ have limited cupboard
space, and once full, all excess glucose molecules
are converted into molecules called ‘fatty
acids’. Fatty acids are then bonded together
as ‘triglyceride’ molecules and
transported to a much larger storeroom with
unlimited space, namely the fatty tissue. The
hormone that is responsible for this process
is called insulin.
contributing to weight gain by stimulating fat
production, fat transportation and fat storage,
insulin also blocks the natural flow of fatty
acids from the fatty tissue to other cells to
be used for energy purposes, thus preventing
you from losing weight.
insulin levels are controlled by blood glucose
levels. The faster and higher blood glucose
levels rise, the more insulin is released. The
(GI) is a new classification of carbohydrates
based on the speed of which individual food
items release glucose into the system and, therefore,
their ability to raise blood glucose levels.
Food items with a high GI value raise blood
glucose levels much faster than food items with
a low or intermediate GI value. If glucose enters
the system at a slower rate, less insulin is
also secreted. The result is that less fat is
factors affect the Glycaemic Index of food.
Individual properties relating to each food
substance, the presence of fat, fibre and protein
in meals (mixed meals) and different food production
or processing techniques are primarily responsible
for these variations.
avoid a sudden rise in blood insulin, one should
eat carbohydrates from the low to intermediate
GI groups, in preference to high GI carbohydrates.
for most of body’s vital functions, including
the growth, maintenance and repair of cells.
It also helps to create enzymes that enables
to digest food, produce antibodies that fight
off infection, and hormones that fight off infection.’
carbohydrates, dietary protein supplies four
calories of energy per gram.
proteins are constructed from smaller sub-units
called amino acids. There are 22 different types
of amino acids and each amino acid has its own
individual structure, function and property.
Most amino acids can be manufactured in the
human body, but ‘essential amino acids’
are those our bodies cannot synthesize on its
own, and that we must acquire from our diet.
dairy and eggs have the entire range of amino
acids, and are therefore called ‘complete
proteins’. Although some plants have substantial
quantities of proteins, they do not always contain
the entire range of amino acids, and are therefore
sometimes referred to as ‘incomplete proteins’.
Vegetarians must therefore combine different
plant products (such as legumes with grains)
to ensure the intake of the entire range of
amino acids. Most amino acids are beneficial
to the body. The amino acid ‘homocysteine’,
however, plays an important role in the development
of hardening of the arteries, and raised homocysteine
blood levels are therefore detrimental.
water, protein is the most abundant substance
in the body. It is the primary component of
our muscles, skin and internal organs. Amino
acids, unlike carbohydrates and fat, are not
stored in the body for energy purposes, but
can be used for energy in certain conditions.
During a period of famine, for example, the
body will first use carbohydrate and then fat
for energy purposes. Only when these stores
are depleted, will the body start using its
is of interest that dietary protein from food
sources do not stimulate the release of insulin,
hence the popularity of the ‘ketogenic’
or ‘high protein’ diets.
role of fats in the diet has excited much controversy
and debate in recent years. Eating too much
of certain types is harmful but others are vital
for the body and can prevent disease.”
main function of fat is to store energy. It
does this so well that one gram of fat contains
nine calories of energy, more than twice the
amount that carbohydrate and protein contains.
a minor function, fat also serves to insulate
the body against cold. (An irritating function
of improved insulation is that less energy is
burnt to preserve or maintain body temperature).
fats consist of smaller sub-units called ‘fatty
acids’, which are in fact just large molecules
made from carbon and hydrogen atoms. A ‘saturated
fat’ contains the maximum number of hydrogen
atoms it can accommodate. It is therefore ‘saturated’
with hydrogen. An ‘unsaturated fat’
simply has space for more hydrogen atoms, and
is therefore ‘unsaturated’ with
hydrogen. For various medical reasons, unsaturated
fats are beneficial to our health, whilst saturated
fats are detrimental to our health.
fatty acids play a crucial role in the human
body, and are called ‘essential fatty
acids’ (EFA’s). Because of these
benefits, they should ideally be consumed on
a daily basis, and without an adequate supply
of these certain disease processes may develop.
are not sources of energy and contain no energy
are also not building blocks and do not form
part of the structure of our bodily tissues.
They do, however, have a very important function,
and assist other chemicals such as enzymes and
hormones when performing a variety of metabolic
and biochemical tasks. They are therefore ‘co-enzymes’,
and are essential for growth, vitality and health.
They also assist with digestion and elimination,
as well as resistance to disease (immunity).
bodies cannot manufacture vitamins, and we therefore
need to ingest them by eating plants and animals
that manufacture them.
vitamins include many of the B vitamins and
vitamin C. They are not stored in the body,
and should ideally be consumed on a daily basis.
vitamins are vitamin A, D, E and K, and are
found in the fatty component of both vegetable
and animal-source foods. These vitamins can
be stored in the fatty tissue of the body, and
have therefore the potential to accumulate and
shortage of certain vitamins can cause disease
and increase the risk of developing many degenerative
vitamins, minerals are not sources of energy
and contain no energy value. They are, however,
extremely important and assist the body with
also known as elements, are basic molecules
that cannot be reduced to simpler substances.
Almost all the Earth’s minerals are present
in our bodies, but some minerals are considered
essential if a deficiency produces symptoms
or illness. These essential minerals can be
divided into bulk minerals (macro-minerals),
which are abundant in the system, and trace
elements (micro-minerals), which are present
in extremely small quantities.
essential macro-minerals are calcium, phosphorous,
sodium, potassium, chloride, sulphur, magnesium
essential trace elements are iron, zinc, copper,
iodine, manganese, chromium, molybdenum and
selenium. (Vanadium, boron and tin are probably
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