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Fibres - Why do we need it and what are the best sources

Fibre, also known as roughage is the indigestible part of plant sourced food that moves through our digestive system, absorbing water along the way and facilitating bowl movements. Dietary fibres refer to nutrients in our diet that do not get digested by gastrointestinal enzymes. 


In this article we shall examine the different types or fibre, discuss their nutritional importance and which foods they come from.

In a nutshell: Here are some key points about fibre. More detail and supporting information is in the main article:

  • Fibre is also referred to as roughage or bulk

  • Fibre is often split into two types: soluble and insoluble

  • Dairy products and white bread are low in fibre

  • Cereal grains, seeds and fruits are high in fibre

  • Gut motility is aided by fibre in the diet

  • Fibre helps speed up the elimination of toxic waste through the colon

  • Insoluble fibre assists in maintaining correct pH range

  • Soluble fibre can reduce cholesterol levels

  • Kidney beans, pinto beans and Brussels sprouts all contain soluble fibre

  • The recommended daily amount of fibre is 25 g for women and 38 g for men.

Soluble and insoluble fibre

Fibre is made up of non-starch polysaccharides, such as cellulose, dextrins, inulin, lignin, chitins, pectins, beta-glucans, waxes and oligosaccharides. The term fibre is often misleading, because many types of dietary fibres are not fibres at all.

There are two broad types of fibre, soluble and insoluble.


  • Soluble fibre which dissolves in water. It changes as it travels through the digestive tract, where it is fermented by bacteria. As it absorbs water it becomes gelatinous

  • Insoluble fibre does not dissolve in water. As it travels through the digestive tract it retains its form.


Dietary fibre foods are generally divided into predominantly soluble or insoluble; both types of fibre are present in all plant foods, but rarely in identical proportions.

Benefits and function of insoluble fibre

Insoluble fibres have several functions, including moving bulk through the digestive tract, and controlling pH (acidity) levels in the intestines.  Their benefits include promoting regular bowel movement and prevention of constipation, speeding up the elimination of toxic waste through the colon, and by keeping an optimal pH in the intestines, they help prevent microbes from producing substances which can lead to colorectal cancer.


Food sources of insoluble fibre include: vegetables - especially dark green leafy ones, root vegetable skins, fruit skins, whole wheat products, wheat bran, corn bran, nuts, and seeds.


Benefits and function of soluble fibre

Soluble fibre binds with fatty acids, slows down the time it takes to empty the stomach as well as slow down the rate the body absorbs sugar. Their benefits include reduction of cholesterol, especially LDL levels (bad cholesterol). In addition it regulates sugar intake, which is especially useful for people with diabetes and metabolic syndrome.


Food sources of soluble fibre include: kidney beans, pinto beans, Brussels sprouts, broccoli, spinach, courgettes, apples, oranges, grapefruit, grapes, prunes, oatmeal, and whole-wheat bread.


How much insoluble and soluble fibre should I eat?

According to the Academy of Nutrition and Dietetics[1] the recommended daily amount of fibre for women is 25g and for men its 38g. However, after the age of 50 it is recommended that women drop their intake to 21g and men to 30g.

Most nutritionists claim that the ratio of insoluble vs. soluble fibre should be 75% to 25%, or 3 parts insoluble to every 1 part soluble. Since most high-fibre containing foods usually have both types, it isn’t really necessary to be too careful about dividing them up.  Oat, oat brans, psyllium husk and flax seed are rich in both types of fibres. In other words, your focus should be on fibre intake in general, rather than on the type of fibre.


If you consume 25g of fibre daily you should meet the recommended daily requirements. Ideally, you should consume 5 servings of fruit and vegetables daily, as well as some servings of whole grain products.


Additional benefits of eating fibre

Most foods which are high in fibre are also very good for other reasons. For example, fruit and vegetables and whole grains, are high in fibre but also rich in vitamins and other essential nutrients. In other words, if you seek a high-fibre diet, not only will you be protecting your health because of your fibre intake, but also because you will be consuming other essential nutrients.

Fibres and food allergies

Apples can be a good source of fibre for people who are allergic to other high fibre foods.


If you suffer from food allergies, which often seem to be high-fibre foods, getting the right amount of fibre can be a bit of a challenge. With such a wide variety of fibre containing foods available, you should be able to find some that you are not allergic to.


When you do find the foods that you can tolerate, you may have to plan in advance more than other people who do not have food allergies. Pharmacies sell fibre supplements, which can help bridge the gap. 


The following high-fibre foods are the least likely to be allergenic: apples, pears, melons, carrots, potatoes, swede, Broccoli, Green beans, pumpkin and courgette.



[1] "It's About Eating Right- Fibre" Academy of Nutrition and Dietetics. Accessed November 4th 2013.

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