Fibre, also known as dietary fibre, is a type of carbohydrate found in fruits, vegetables and whole grains. It is made up of the parts of plants that cannot be broken down by human digestive enzymes in our small intestine, and therefore not absorbed into the body. However, some dietary fibre is partially or completely digested by bacteria in our large intestine (colon).

Dietary fibre is only found in plant products – animal products such as meat, dairy, and eggs do not contain fibre.

Types of Fibre

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

Soluble Fibre

Soluble fibres dissolve in water and gastrointestinal fluids to create a gel-like substance. They help to prevent and relieve constipation.

Insoluble fibre

This fibre is not digested by the body, thus remains unchanged as it moves through our intestines. Insoluble fibre absorbs water which bulks out stools, making them softer and easier to pass through the digestive system to maintain regular bowel movements.

Most plant foods contain both soluble and insoluble fibre, however the amount of each varies between foods. Therefore, you should try and eat a range of plants to maximise the health benefits of fibre.

How much fibre should I be eating?

Fibre intake depends on age.

The recommended intake for adults is 30g per day, however recent studies have shown that the average adult in the UK only consumes 18g fibre a day – 60% of the daily recommendation!

For people under 18 years old, the recommended daily intake is:

Foods that have 3g or more of fibre per 100g are classed as a source of fibre. To be high in fibre, foods need to contain at least 6g fibre per 100g. To check the fibre content of packaged foods, check the label on the back of the packet - fibre is not currently listed as one of the nutrients on the front of pack labels.

What does 30g fibre look like?

Here’s an example of how to get your daily intake of fibre.

 Source McCance & Widdowson v7

Why should I include fibre in my diet?

Diets high in fibre (30g or more a day) have been linked to a range of health benefits.

Blood sugar control

Insoluble fibre delays the absorption of sugar into the bloodstream from the intestine, helping to prevent spikes in blood sugar, and improve glucose management for people living with Type 2 diabetes. The evidence for this has been specifically for diets high in cereals and wholegrains.

Digestive Health

Fibre is very important for good gut health. It helps to regulate bowel movements and alleviates symptoms of diarrhoea and constipation. Evidence suggests that eating  a diet high in fibre is linked to lower risk of diverticulitis (inflammation of, and damage to the bowel), and colorectal cancer.

Heart Health

There is good evidence to suggest that soluble fibre can help to reduce total blood cholesterol and LDL (low density lipoprotein), also know as ‘bad’, cholesterol. It prevents some cholesterol from the diet being digested and absorbed into the body.

Gut microbiome

In recent years, research has shown that our gut microbiome (see our article on Gut Microbiome) can have an impact on our overall health. The gut microbiome plays a role in regulating cholesterol and gut hormones, neurological signalling, digesting food, and immunity.

Fermentable fibres from plants provide food for the large number of bacteria found in our large intestine. These bacteria break down the fibres to produce compounds called short-chain fatty acids (SCFAs). These SCFAs provide food for the cells in our gut wall, in addition to regulating certain hormones which play a role in appetite and glucose metabolism. SCFAs also help to maintain the mucus which lines our gut wall, forming a barrier between the content of our intestines and the rest of the body.

So how can I increase my fibre intake?

• Eat at least five portions of different fruit and vegetables a day – try to ‘eat the rainbow’ and include as many different coloured foods on your plate as possible. You can find out what counts as a portion for one of your five a day here.
• Leave the skin or peel on fruits and vegetables; remember to wash them before eating or cooking.
• Swap white pasta, rice and bread for wholegrain varieties.
• Include beans and pulses in your diet. In addition to fibre, they contain protein which will leave you feeling fuller for longer.
• Drink six to eight glasses of fluid a day to avoid dehydration. Fibre pulls water into your gut, so you need to ensure that you drink enough.
• Look at the labels on packaged foods – foods need to have at least 3g fibre per 100g to be classed as a source of fibre.

The table below shows how some small changes can make a BIG difference to your fibre intake!

Source McCance & Widdowson v7

If you are planning to increase your fibre intake, ensure that you do it gradually to allow your digestive system to adapt. A rapid increase in fibre in your diet can lead to unwanted symptoms such as gas and bloating.  

Sources

BDA (2024) Fibre

BNF (2021) Fibre

BHF (2024) Are you eating enough fibre?

Nourished Life (2024) Fibre Facts