What is the difference between fibres and cellulose?

Cellulose makes up cell walls in plants and can be digested by some animals such as termites but not by humans. Cellulose is often referred to as dietary fibre in the area of human consumption. Other types of fibre are natural and man-made fibres such as cellulose cotton, linen, fibreglass and nylon. Fibre generally refers to a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.

Even though humans cannot digest dietary fibre (also known as roughage or ‘bulk’), it is important for normal digestive function. High-fibre foods help move waste through the digestive tract faster and easier, so possibly harmful substances do not have as much contact with the gastrointestinal tract and reduce straining. Fibre in the diet also increases the likelihood of regular bowel movements.

There are two principal types of dietary fibre: soluble and insoluble. The major roles of soluble fibre are to lower blood cholesterol levels and help prevent heart disease. Good sources of soluble fibre include fruit, vegetables, oat bran, barley and soy products. Soluble fibre can also help with constipation and diarrhoea. Although. Insoluble fibre’s major role is to add bulk to faeces and to prevent constipation and associated problems such as haemorrhoids. Good sources include wheat bran, corn bran, rice bran, the skins of fruits and vegetables, nuts, seeds, dried beans and wholegrain foods. But remember - a diet high in fibre may not prevent or cure constipation unless you drink enough water every day.

Another type of fibre is resistant starch. It doesn't get digested and ends up as food for bacteria in the large intestine. It's thought to act in a similar way to traditional fibre to improve bowel health. Resistant starch is in foods such as unprocessed cereals and grains, firm bananas, lentils and potatoes.

Main conditions linked to low fibre diets:

Eating a diet low in fibre can contribute to many disorders, including

• Constipation - small, hard and dry faecal matter that is difficult to pass.
• Haemorrhoids - varicose veins of the anus.
• Diverticulitis - small hernias of the digestive tract caused by long term constipation.
• Irritable bowel syndrome - pain, flatulence and bloating of the abdomen.
• Overweight and obesity - carrying too much body fat.
• Coronary heart disease - a narrowing of the arteries due to fatty deposits.
• Diabetes - a condition characterised by too much glucose in the blood.
• Colon cancer - cancer of the large intestine.

Current recommendations suggest that adults consume 20-35 grams of dietary fibre per day. You can increase your fibre intake by: eating breakfast cereals that contain barley, wheat or oats; switching to wholemeal or multigrain breads and brown rice; adding an extra vegetable to every evening meal and by snacking on fruit, dried fruit, nuts or wholemeal crackers.