Family doctor


Bowel And Abdominal Problems

FIBRE - a patient's guide


This article outlines the different types of fibre and its role in treating certain conditions such as constipation, high cholesterol, diabetes and in probably reducing the risk of bowel cancer. Useful tips on how to eat more fibre are provided.



  • 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?


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.


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.


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.


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.

See also:

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