Alternative Names dietary fibre, soluble fibre, insoluble fibre, psyllium
Definition Fibre is the part of plant foods that cannot be digested by humans. Its chemical properties make it a carbohydrate. However, because it cannot be digested, it provides very little kilojoules to the diet.
What food source is the nutrient found in? There is no recommended daily amount of fibre. Most health experts recommend getting 30 to 35 grams per day. Most Australians eat about 18 grams per day.
There are two types of fibres. There are soluble fibres and insoluble fibres. They both have very different functions in the body.
Common sources of soluble fibre include:
zucchini
apples
(porridge) and oat bran
baked beans and other hard beans
citrus fruits
barley and barley bran
peas
many vegetables
psyllium seed
Common sources of insoluble fibre include:
breakfast cereals
wheat bran and bran cereals
flax seed
strawberries
potatoes
capsicum
whole-meal and whole-grain products
Grains that have been refined, for example whole-meal flour that is refined to white flour, have had the fibre removed. Whole-meal flour is a good source of fibre. White flour is not. Be aware that just because bread is brown does not mean it is high in fibre. Look for the words, "whole-meal" or "whole-grain" to make sure the product is made with wheat flour and has fibre in it. Some white breads now have fibre added, so look for high fibre white.
How does the nutrient affect the body? Soluble fibre dissolves in water. Soluble fibre can help reduce cholesterol levels. In the body, these fibres bind with bile acids, which are made from cholesterol. When bile acids are bound to fibre they are excreted, causing more cholesterol to be converted to bile acids. This leads to an overall lowering of blood cholesterol levels. The effect may be subtle, but even a small drop in blood cholesterol levels can protect against heart disease. Soluble fibres also help regulate the body's use of sugar. This can help to regulate blood sugar levels.
Insoluble fibre or roughage, does not dissolve in water but it can absorb water. This makes it the perfect bulking agent for faeces (or stool). Bulking agents improve bowel function by increasing the bulk of stools, which hurries the stool through the gastrointestinal (GI) tract. This can help promote regularity. This can also help prevent constipation, haemorrhoids and diverticulosis. Increasing insoluble fibre can help dieters by prolonging the feeling of being full. This can help them cut down on snacking after meals. Some scientists believe that insoluble fibre can aid in protecting against bowel cancer. Increased bulk and a faster GI system may minimise the exposure of potential cancer-causers to the GI environment. Bacteria in the bowel also ferment fibre to produce gases and fatty acids, some of which are thought to slow down cancer cell growth.
Information Many over-the-counter fibre supplements are available and widely used. One of the common ingredients in these products is psyllium seed husk. This is a soluble fibre. Psyllium is effective in reducing cholesterol levels.
Increased fibre intake should be done gradually. Fibre can cause increased gas and bloating. It is also important to drink lots of water when on a higher fibre diet or when increasing fibre in the diet. Water helps to move the fibre through the system. Aim for at least eight glasses per day (2 litres), more if it is hot or you are physically active.
There are many things people can do to increase the fibre in their daily diet:
Reading food labels can help increase the amount of fibre in the daily diet.
Choose high fibre breakfast cereals and eat a bowl every morning. Look for cereal that contains at least 3 grams or more of fibre per serving.
Switch to whole-grains breads, whole-meal pasta and brown rice.
Eat dried beans at least two to three times per week. They are great in soups or salads.
Eat at least two servings of fruits and five servings of vegetables daily.
Leave the edible skin on fruits and vegetables, which supplies fibre too.
Choose whole fruit rather than fruit juice as often as possible. Fibre is found in the peel and pulp; both of which are usually removed when the fruit is made into juice.
Author: Clare Armstrong, MS, RD Reviewer: HealthAnswers Australia Medical Review Panel Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia Last Updated: 1/10/2001 Contributors Potential conflict of interest information for reviewers available on request
