Your fibre FAQs answered

Put simply, fibre – also known as ‘roughage’ – is a complex carbohydrate, derived from plants, which the body cannot digest.

Enzymes are constantly working to break down the food you eat. These enzymes are released by your digestive system (mainly by your pancreas and small intestine) and convert carbohydrates, proteins and fats into nutrients which are then absorbed into your body to support its healthy function. 

Fibre, however, is not broken down by digestive enzymes in the way that carbs, proteins and fats are. Fibre’s role in a healthy diet is to make the digestive process itself smooth and effective.

Broadly, there are two types of fibre- soluble and insoluble. 

Soluble fibre attracts water as it moves through the small intestine, creating create a gel-like substance as it passes through into your large intestine. This softens your stool and adds bulk as well as binding with unwanted particles (e.g. cholesterol or sugar) to aid their elimination from the body. According to recent research, a type of soluble fibre called resistant starch ferments in the large intestine, feeding the gut with ‘good’ bacteria in the same way as a prebiotic and producing short-chain fatty acids which are beneficial to health.

Insoluble fibre adds further bulk and gives form to your stool, binding indigestible waste products together and encouraging your stool to move more swiftly and completely through the large intestine. This type of fibre is what people usually think of as ‘roughage’.

According to UK government guidelines, adults should be getting 30g fibre a day. Around 9 in 10 people in the UK are not meeting this with most adults eating an average of 18g a day. 

Insufficient fibre intake can cause constipation, bloating and loose stools, along with a general feeling of sluggishness. The undigested food, waste products and bacteria hang around in your gut for longer without being eliminated, which can cause inflammation. Additionally, a diet lacking fibre can lead to weight gain, as without fibre to make us feel full, we are at risk of overeating.

Despite most people not getting enough, it is possible to eat too much fibre. Warning signs include constipation, feeling ‘blocked up’ and bloated, gas and stomach cramps. If you switch from a low-fibre diet to a high-fibre diet too quickly, you could experience digestive discomfort- so it is always best to increase high-fibre foods gradually until you reach the recommended 30g fibre daily.

Fibre is easily and abundantly found in a range of delicious and nutritious foods. So, what foods contain fibre? The best fibre foods are often convenient and cheap, e.g. fruits, vegetables, whole grains and legumes. There is 4.4g fibre in a medium apple and 3.1g fibre in a banana. Other foods that are high in soluble fibre include oats, peas, beans, citrus fruits, carrots, barley and nuts. Insoluble fibre can be found in wheat bran, brown rice, cauliflower, potatoes, tomatoes, cucumbers, carrots and nuts. Sources of resistant starch include green bananas, white beans and lentils.

Last updated: 17 March 2020