What is fibre?

Fibre is a vital part of the digestive process, but are you eating enough? Dietitian/nutritionist Vanessa Jones shows how, by making small changes in what you eat, you can easily go from a low-fibre diet to one that is high in fibre.

Your mother describes it as ‘roughage’, the kids call it ‘those yucky grainy bits’ and your partner scoffs and labels it ‘horse feed’. The word ‘fibre’ often conjures up thoughts of scratchy, hard bits found in tasteless food which has one purpose – to keep you regular. But fibre is often invisible, does a lot more than keep the bowels moving, and is definitely not confined to food stored in chaff bags in the stables.

Dietary fibre – not a nutrient but still a vital part of our diet – is only found in foods of plant origin such as breads, cereal products, fruits, vegetables, legumes, seeds and nuts. The key feature of fibre is its ability to pass through the stomach and small intestine undigested and reach the large intestine virtually unchanged. Most other food components and nutrients we eat are digested and used in other parts of the body before this stage.

However, fibre is not ‘indigestible’. In the large intestine, some components of fibre are broken down by millions of ‘friendly’ bacteria. As part of this process, the bacteria multiply by the million and produce special acids. Once they die, their bodies add bulk to our faeces and are excreted. This is a natural and desirable process. In fact, one of the acids produced (butyric acid) has been shown to have cancer-preventing properties within the bowel.

Just as there are different types of vitamins, there are also different types of fibre, ‘soluble’ or ‘insoluble’, both playing a different role in the body.