What is dietary fibre?

The Scientific Advisory Committee on Nutrition (SACN) 2015 defines fibre as:

“All carbohydrates that are naturally integrated components of food that are neither digested nor absorbed in the small intestine and have a degree of polymerisations of three or more monomeric units, plus lignin.”

If we are to put that in a simpler way, fibre is the term used for plant-based carbohydrate foods that are not digested in the small intestine and therefore reach the large intestine (or bowel) undigested.

You may have heard the terms soluble and insoluble fibre before. These refer to whether or not the fibre dissolves in the stomach. It is important to remember that fibre-rich foods typically contain both types of fibre and we should aim to increase fibre as a whole in our diet.

What are the health benefits of fibre?

The summary of evidence from the World Cancer Research Fund’s (WCRF) Continuous Update Project 2018 states that “there is strong evidence that consumption of wholegrains protects against colorectal cancer, and consumption of foods containing dietary fibre protects against colorectal cancer and against weight gain, overweight and obesity”.

Fibre and bowel cancer

In the UK 28% of bowel cancer cases are caused by eating too little dietary fibre (Brown et al, 2018). The reasons for the protective mechanisms are not yet fully understood, but is it likely related to that fact that fibre bulks stool mass and so helps to move waste products through the gut faster and so it has less time in contact with the bowel. Some types of fibre may also provide a food source for our ‘friendly’ gut bacteria and the area of probiotics and prebiotics is of interest to researchers. With further evidence we may be able to advise on supplementation and dosage in the future.

Fibre and cardiovascular disease (CVD)

The World Health Organisation has estimated that over three-quarters of CVD deaths may be preventable by appropriate lifestyle change (WHO, 2003). This includes making changes to unhealthy lifestyle factors such as smoking, low levels of physical activity and poor diets. According to research for each additional 7g dietary fibre consumed, the risk of CVD is reduced by about 7–9% (Stephen et al, 2017).

Fibre and type 2 diabetes

With a 6% reduction in diabetes risk for each 7g/day increase in total fibre consumed findings from recent studies support recommendations to increase fibre intake. (Threapleton et al., 2013).

Higher fibre foods also tend to have a lower glycaemic index which means they release their energy more slowly and keep you feeling fuller for longer. Intervention studies looking at the effect of dietary fibre on appetite-related outcomes have had inconsistent results however.

Table 1:

Recommendations for all age groups

Age Group Dietary Fibre Recommendation
Under 2 years No quantitative recommendations are made for children aged under 2 years, due to the absence of information, but from about six months of age gradual diversification of the diet to provide increasing amounts of whole grains, pulses, fruits and vegetables is encouraged.
2-5 years 15g / day
5-11 years 20g / day
11-16 years 25g / day
16-18 years 30g / day
Adults 30g / day

Source: Scientific Advisory Committee on Nutrition. Carbohydrates and Health, 2015

How can we tell if a food is high in fibre?

Nutrition claims can only be made if they are listed in the Annex of Regulation (EC) No 1924/2006:

  • A claim that a food is high in fibre may only be made where the product contains at least 6g of fibre per 100g or at least 3g of fibre per 100 kcal.
  • A claim that a food is a source of fibre may only be made where the product contains at least 3g of fibre per 100g or at least 1.5g of fibre per 100 kcal.

Here are our top 3 #HUSTLEHINTS to get more fibre in your diet…

  • Choose a higher fibre breakfast cereal such as Weetabix, Shredded Wheat, All Bran or oats

  • Add pulses like beans, chickpeas & lentils and some extra veg to salads, soups, curries and casseroles.

  • For snacks choose fruit, raw veg, unsalted nuts & seeds, oat cakes or rye crackers.