It used to be called "roughage", and people tried to get rid of it.  Now we all know we need fibre in our diet, but why?

In this section, you will find out what dietary fibre is, why we need it, what it does for us and where we find it in our foods.

Why do we need dietary fibre?

Dietary fibre refers to the carbohydrate that does not get digested by enzymes in our small intestine, and so its sugar units are not absorbed into the bloodstream.  Dietary fibre is therefore known as 'non-glycaemic'.

However, fibre has important effects on other nutrients within the small intestine and through effects on the large intestine, where few other nutrients arrive intact.  It has a range of valuable health effects:

• Smooths out digestion and absorption of glucose and fats in the small intestine.  It reduces the Glycaemic Index of a meal.
• Provides fuel for the healthful or "good" bacteria in our large intestine which in turn benefit us by making vitamin B12, and by releasing volatile fatty acids from the dietary fibre which are important for the health of our colon.
• Speeds up transit though the intestines to remove waste and toxins from our body
• Regulates bowel action, so reducing cancer risks

Did you know?  Dietary fibre has been sold for years as a 'bulking agent' as people thought it must reduce appetite and help weight loss.  But research shows that it doesn't actually reduce appetite or assist weight loss directly.   

So, what is dietary fibre?  Find out more by clicking that link.

Where do we find dietary fibre in our food?

Generally, dietary fibre is present in all plant foods - fruits, vegetables and grains - but not in animal foods.  This is mainly because of the different in cell structures - plants cells have cell walls, animal cells don't.

Insoluble fibre can be found in foods such as wheat, corn, wholemeal bread, brown rice, bran, whole grain cereals, nuts and seeds, vegetables and peels of fruits.

Soluble fibre is particularly rich in legumes - lentils and peas and beans (including peanuts) and bean products like 'soya protein' - and in oats, barley, fruits, vegetables and potatoes                                  

Is there a down-side?  Can you have too much dietary fibre?

Well, yes you can…

First, some advice for you if you want to add more fibre to your diet…  Increase fibre-rich foods gradually, because a sudden large addition of fibre into your diet can cause stomach cramps and wind.  Your intestine will adapt in time.

And, too much dietary fibre can interfere with the absorption of minerals such as iron, zinc and calcium from foods.  This is not often a problem because high-fibre foods usually contain plenty of these minerals, and vegetarians on very high fibre diets tend to be healthy, but it can cause problems when the overall diet quality is poor.  If you are taking fibre supplements, be careful and only use them occasionally.

It's important to always make sure that you keep yourself well hydrated in relation to your fibre consumption, because fibre can dehydrate you a little and become sluggish in your system. 

So we can see that dietary fibre has lots of plus-features, but it can have a few minuses too.  Our health depends on eating a balanced diet- and it can sometimes be a bit tricky to work out all the pluses and minuses of all the nutrients.

See also What is dietary fibre?