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All the nutrients the body needs can easily be obtained from a
vegetarian diet. In fact, research shows a vegetarian diet can be
healthier that that of a typical meat eater. Nutrients are usually
divided into five classes: carbohydrates, proteins, fats and oils,
vitamins and minerals. We also need some dietary fibre and water. All
are needed in varying quantities, from about 250g of carbohydrate per
day to less than two micrograms of vitamin B12.
Most foods contain a mixture of nutrients, but it is convenient to classify them by the main nutrient they provide.
Girls aged 15-18 years need around 45g of protein a day (more, if
very active or lactating) and boys aged 15-18 need about 55g (more if
very active). Too much protein may aggravate poor or failing kidney
function. Vegetarians obtain protein from four main sources: - Nuts and
Seeds - Peas, Beans and Pulses - Grains and Cereals - Dairy and Eggs
The humble Soya bean is an excellent source of vegetarian protein and
is found in veggie bacon, tofu, pot noodles, sausages and sauces! It
can be made into milk and other dairy substitutes for vegans. It is
also consumed widely by omnivores as soya is found (as a bulking agent)
in 70% of processed foods. It is maintained by some that it is
necessary to 'combine' the proteins in a vegetarian diet to obtain an
adequate supply of amino acids, eight of which are essential for adults
and nine for children. Vegetarian proteins are usually deficient in one
of the eight essential amino acids, so some people advise that we
combine the proteins we eat in a meal or throughout the day to achieve
a full complement. Any two of the protein groups in the diagram above
can be combined to achieve a full complement of protein. Meals such as
beans on toast, or cereal and milk are excellent examples of how
proteins can be easily combined to create the full complement of amino
acids. The latest research suggests that the body has a short term pool
of amino acids and, because of this, we don't have to worry about
complementing amino acids at every single meal, as long as our diet is
varied and well-balanced. Even foods not considered to be very high in
protein are adding some amino acids to this pool.
Carbohydrates give us energy. There are three main types of
carbohydrates: simple sugars (monosaccharides), complex carbohydrates
or starches(disaccharides), and dietary fibre (non-starch
polysaccharides or NSP). Simple sugars are found in fruits (intrinsic
sugars), milk (lactose) and ordinary table sugar. Refined sugars
(non-milk extrinsic sugars) are best avoided, as they provide energy
without any associated nutrients - they are empty calories - and are
the main cause of dental decay. Complex carbohydrates are found in
starchy foods such as bread, rice, pasta, oats, barley, potatoes and
parsnips. A high intake of complex carbohydrates is an important
component of a healthy diet. Unrefined foods such as wholegrain breads
and brown rice are best of all as these contain dietary fibre and B
vitamins. Starchy foods are very filling relative to the number of
calories they contain and so form an essential part of a slimming diet.
Dietary fibre or NSP, refers to the indigestible parts of a
carbohydrate food. Fibre is found in fresh and dried fruits, whole
foods such as wholegrain cereals and wholemeal breads and vegetables.
Fibre in the diet protects against digestive disorders by keeping the
system clean. We need about 11g of fibre per day for a healthy
digestive system.
Too much fat - especially saturated fat - is very bad for us, but
some fats and oils are necessary in the diet to keep our tissues in
good repair, for the manufacture of hormones and to act as a carrier
for some vitamins. Like proteins, fats are made from smaller units,
called fatty acids. The way in which the acids form compounds
determines whether they are saturated, monounsaturated or
polyunsaturated. Saturated fats come mainly from animal sources and
include lard and butter and also a few plant sources such as palm oil.
Vegetable fats tend to be unsaturated. Monounsaturated fats include
oils such as olive oil and groundnut oil. Polyunsaturated oils include
sunflower oil. Linoleic and linolenic acids are the essential fatty
acids and are found in cold-pressed oils such as maize (corn), soya and
sunflower seed oils, nuts and avocados. Vitamins are micro-nutrients
that cannot be synthesised by the body in sufficient amounts for
health. Therefore we must ensure an adequate supply in the diet.
Vitamins A, D, E and K are fat-soluble vitamins; Vitamin C and the
B-complex are water soluble. Vitamins in food must be looked after
carefully otherwise they will be lost. You can eat as many overboiled
and soggy carrots and sprouts as you like - but they won't do you much
good! Vitamins A, C and E are often referred to as antioxidants. This
means they help to protect the body from reactive oxygen species (free
radicals) which are produced by the body's normal metabolic processes.
If free radicals accumulate they can damage key DNA molecules and
proteins. This process may be responsible for some cancers. It has been
shown that those consuming large amounts of vitamin rich orange and
yellow fruits and dark green and orange vegetables seem to be less
prone to some forms of cancer. It is recommended that we eat five
portions of fruit and vegetables a day. Girls aged 15-18 need 600
micrograms of Vitamin A per day and boys aged 15-18 need 700
micrograms. Betacarotene is the vegetarian form or precursor of Vitamin
A and retinol is the form found in meat and animal products.
Betacarotene is converted to retinol in the body. Vitamin A is
essential for good night vision and prevents eye disorders such as
night-blindness and severe eye-lesions. It is also needed for healthy
skin tissues, especially those excreting mucus.
Red, orange and yellow
vegetables such as carrots, peppers, mangoes, and sweet potatoes are
excellent sources of betacarotene. Green leafy vegetables also provide
a source. Animal foods such as cheese also contribute to our intake.
The B-Vitamin Complex. These help us to convert the carbohydrates in
our food into energy, are needed for the metabolism of amino acids, for
rapidly dividing cells and the metabolism of fat. Deficiencies can lead
to beriberi (thiamin), pellagra (niacin) and megaloblastic anaemia
(B12). As the B vitamins act as co-factors in different enzyme-systems
in the body, diets lacking in B vitamins may lead to multiple
deficiency diseases within a few months. B Vitamins include B1
(thiamin), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B12
(cyancobalmin), folate, pantothenic acid and biotin. The entire
B-Vitamin complex except B12 occurs in yeasts, wholegrain cereals
(especially wheatgerm), nuts, pulses, seeds and green leafy vegetables.
Vitamin B12 may cause some difficulty, as it is usually not present in
plant foods. Only very tiny amounts are needed and vegetarians can
usually obtain this from dairy produce and eggs. Vegans and vegetarians
consuming few animal foods should include foods fortified with B12 such
as Marmite, soya milks, veggieburgers and some breakfast cereals.
Girls
and boys aged 15-18 both need 40mg of Vitamin C per day. Vitamin C is
plentifully and easily available in a vegetarian diet full of fresh
fruit such as blackcurrants and strawberries, orange and other fruit
juices, peppers, salad vegetables, leafy greens and potatoes. Vitamin C
is necessary for healthy connective tissues. Deficiency can result in
bleeding, slow wound healing and scurvy, a skin disease. Vitamin D is
needed for the absorption of calcium from the intestine and to deposit
the calcium in the bone - mineralisation. Vitamin D is not found in
plant foods but humans can make their own supplies in the skin when it
is exposed to sunlight. Vitamin D is added to margarine's and is
present in milk, cheese and butter. Deficiencies can occur in those
confined indoors and to women whose religion requires their skin to be
fully covered. These may lead to rickets in children and osteomalacia
(bone softening) in adults. Vitamin E's main use in the body is as an
antioxidant. It is widely available in cold pressedoils, wholegrain
cereals and eggs. Vitamin K is necessary for the normal clotting of
blood. Supplements are often given to babies at birth. Vitamin K is
produced via bacterial synthesis in the intestine, and dietary sources
include fresh vegetables, cereals and grains. Girls aged 15-18 years
need 800mg of calcium per day. Boys aged 15-18 need 1000mg per day.
Calcium, in partnership with magnesium, builds a healthy skeleton and
strong teeth. Calcium is also needed for muscle contraction (including
the heart muscle), nerve function, blood clotting and the activity of
several enzymes. Sources of calcium include dairy produce, leafy green
vegetables (particularly watercress), white bread, sesame seeds and
dried figs. Vitamin D is essential for the absorption of calcium.
A diet high in saturated fats can lead to calcium leaching from the
bones. Deficiencies of calcium in the diet are apparent around the time
of the menopause, when heavy losses of calcium can lead to osteoporosis
or brittle bone syndrome in women. Girls aged 15-18 need 15mg of iron
per day, and boys aged 15-18 need 11.3mg. It is especially important
for teenage girls to ensure an adequate intake of iron. Iron is needed
to maintain the supply of red pigment (haemoglobin) in the blood, which
carries oxygen from the lungs to the tissues, and a deficiency will
lead to anaemia. Vegetarian sources of iron include fortified breakfast
cereals, wholemeal bread, plain chocolate, eggs, leafy greens, lentils
and pulses. Vegetarian sources of iron are not as easily absorbed as
animal sources, but the rate of absorption can be greatly increased by
eating iron rich foods with Vitamin C rich foods. Eating a handful of
dried apricots and brazil nuts with a glass of fruit juice can bolster
a healthy varied diet with extra iron. Zinc is essential for wound
healing and is also involved in enzyme activity. It is mainly present
in the bones. Girls aged 15-18 need 7.0mg of zinc per day and boys aged
15-18 need 9.5mg. Zinc plays a role in many enzyme reactions and in the
health of the immune system. It is found in cheese, sesame and pumpkin
seeds, lentils and wholegrain cereals.
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