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FIBRE - a patient's guide
Paula Messer - Dietitian, Southampton, UK
Overview
Over the decades, studies have shown the importance of
fibre in our diet.
It has been shown to have a positive role in both the
prevention and treatment of certain disease states.
Fibre does not have a particularly appealing image and
most people will think of bran when the word "fibre" is
mentioned.
Fibre naturally occurs in a wide range of foods and these
can easily be incorporated into our daily diet.
Fibre-containing foods will also provide us with more
vitamins and minerals and other substances that have positive
health benefits.
What is it?
Fibre is a mixture of the non-digestible carbohydrate
part of a plant that passes unabsorbed through our body
(e.g. fruit, stems, leaves, and seeds).
There are two main types of fibre in our diet: soluble
and insoluble.
All plants contain both types of fibre but can be higher
in one type than the other.
Insoluble fibre passes through the body mostly unchanged
but absorbs water and consequently swells, resulting in
a bulkier stool. Wholegrain wheat and rye are rich in insoluble
fibre.
Soluble fibre, however, is broken down once it reaches
the large bowel. The natural gut bacteria feed and multiply
on this broken down fibre resulting in softer, bulkier stools.
Oats, barley and pulses are high in soluble fibre; fruit
and vegetables are roughly an equal mixture of both.
How much should you eat?
The recommended daily intake of fibre is 30 gms per day.
Many people do not manage to achieve this, particularly
in western countries where a lot of low-fibre refined foods
are eaten.
Children should not be encouraged to have too high a fibre
intake, especially those under two, as the high fibre foods
replace those that provide energy for growth.
It is unlikely that you can consume "too much" fibre but
studies have shown that in individuals who have excess raw
wheat bran, absorption of certain minerals is prevented.
How to eat more:
Aim for at least 5 portions of fruit and vegetables per
day
Have a wholegrain breakfast cereal - you can add fresh
or dried fruit to this to further increase the fibre content
Eat wholemeal or granary bread or rolls instead of white
Use brown or wholegrain rice instead of white
Use wholewheat pasta instead of white or green
Use a wholemeal flour or a mixture of white and wholemeal
flour when baking
Add lentils, beans or pulses to stews, soups and casseroles
Chopped or grated vegetables and beans can be added to
salads
Increase the amount of fibre in your diet very slowly
otherwise you could suffer from abdominal discomfort. Also
ensure you are having an adequate fluid intake.
How can fibre be beneficial?
Constipation
Fibre helps to keep the bowel healthy and functioning
regularly. This is due to the increased bulk and softness
of the stool from the increased water absorption and bacterial
growth as described above. The increased bulk causes the
stool to be moved quickly through the digestive system and
because the stools are softer, they are expelled easier
than small, hard ones.
Untreated constipation can lead to further problems such
as diverticular disease.
Weight control
Foods high in fat and/or sugar e.g. chocolate, sweets,
crisps and biscuits provide us with a sensation of fullness
and satisfaction almost immediately, but unfortunately this
feeling does not last very long and we are hungry again.
These foods are very high in energy and an excessive intake
leads to weight gain.
A diet high in fibre-rich unrefined carbohydrates e.g.
wholemeal bread, wholewheat pasta and wholemeal cereals
will provide us with a longer lasting feeling of fullness
and a consequent decreased intake of high energy foods.
This is due to the insoluble fibre swelling during digestion
as it absorbs water, physically making us feel full, and
the slow but continual release of energy into the body as
these foods are broken down.
Diabetes
It is especially important to have a good intake of fibre-rich
unrefined carbohydrates when you have diabetes. They are
absorbed more slowly into the bloodstream after digestion,
therefore, helping to maintain a normal blood glucose level.
The soluble fibre forms a sticky gel when it absorbs fluid
and this gel can slow down the rate at which sugar is released
into the bloodstream.
Refined carbohydrates e.g. sugar will cause an immediate
rise in the blood glucose level but consumed with a fibre
containing unrefined carbohydrate, the effect will be less
e.g. jam spread on a slice of wholemeal bread.
Cholesterol
It has been found that a high intake of fibre, especially
soluble fibre, can help lower cholesterol levels.
The mechanisms behind this are not fully understood.
People with a higher cholesterol level appear to benefit
more from an increased fibre intake than those with slightly
raised cholesterol levels.
Cancer
Evidence over the last 30 years has led us to believe
that dietary fibre has a protective effect against colorectal
cancer. Studies carried out in countries that had a high
intake of fruit, vegetables and cereals were found to have
a low incidence of chronic bowel diseases, including cancer.
As mentioned previously, a high-fibre diet provides bulkier
and more frequent stools, decreasing the transit time through
the gut. This decreases the amount of time that the colon
is exposed to naturally occurring carcinogens that are found
in the faecal stream.
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