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Fibre

Published by Bupa's health information team, healthinfo@bupa.com, April 2008

Fibre is the word used to describe complex carbohydrates that can't be fully digested by the body. Although fibre contains no calories, vitamins or minerals, it is vital for your health.

What is fibre?

Fibre is only found in the cell walls of plants. Foods from animals, such as meat, fish, eggs and dairy products, contain no fibre at all. Fibre is made up of a number of complex carbohydrates and can be roughly divided into two different types: insoluble and soluble. Insoluble fibre tends to pass through the gut undigested, while soluble fibre is broken down by bacteria once it reaches the large bowel.

What does fibre do?

Fibre, which used to be known as 'roughage', is essential for healthy bowel function. When fibre passes through your bowel, it absorbs a lot of water and increases the bulk of any waste matter. It also makes the waste softer and increases the speed and ease with which it passes through your bowel.

Why is fibre important?

A diet that is rich in fibre has lots of health benefits. Firstly, it reduces the risk of a number of bowel problems, some of them quite serious. These include constipation, diverticular disease (when the bowel wall becomes inflamed and damaged) and cancer of the large bowel (colon).

Soluble fibre also helps to stabilise your blood sugar levels because it slows down the rate at which glucose is absorbed into your blood stream. This is particularly helpful if you are diabetic. Fibre also helps to lower your blood cholesterol levels, which in turn reduces your risk of heart disease.

Another benefit of fibre is that it makes you feel full, which can help people to control their appetite if they are trying to lose excess weight.

How much fibre should we eat?

Adults should aim to eat at least 18g of fibre a day, but this figure only refers to one kind of fibre that we eat, known as non-starch polysaccharides (NSP). However, this recommendation is now under review because some experts believe this intake should include other types of fibre as well. This would bring the recommended amount of fibre for adults up to about 24g per day. Some studies show that fibre intake may need to be increased to 30g per day to protect health.

In the UK most people eat far too little fibre. The average person eats just 12g per day. Perhaps it's not surprising then, that one to two in every 10 people suffers with constipation.

If you do increase your fibre intake, it's best to do it gradually. A sudden increase may produce wind, bloating and stomach cramps. It's also a good idea to drink plenty of fluids, so that the fibre has something to absorb.

More is not always better. At very high levels fibre can stop having a beneficial effect and may even reduce your body's ability to absorb certain minerals from your food.

Which foods contain fibre?

All plant-based foods contain fibre, but some contain more than others. Good sources of fibre include fruit, vegetables, wholegrain rice and pasta, wholemeal bread, wholegrain breakfast cereals, nuts, seeds and bran. Fruit, vegetables, beans, lentils and oats are particularly good sources of soluble fibre, while wholemeal bread, brown rice, wholegrain breakfast cereals, fruit and vegetables are all good sources of insoluble fibre.

Check the food labels when you go shopping. Labelling regulations allow foods containing at least 3g of fibre per 100g to be labelled as a source of fibre, and foods containing 6g or more to be labelled as high in fibre. Aim for a varied range of foods, to make sure you get a good mixture of both soluble and insoluble fibre.