Dietary fibre is a polysaccharide found in the cell walls of vegetables, fruits, pulses and cereal grains. The dietary fibre cannot be broken down by the digestive system so passes through the intestine, absorbing water and increasing in bulk. The process helps to strengthen the muscles of the intestine and push out undigested food.
Functions: Dietary fibre is needed for:
- Allowing the digestive system to remain healthy and function properly.
- Helping weight control as high fibre foods release energy slowly leaving us feeling fuller for longer.
- Preventing some bowel diseases, for example, constipation, diverticulitis and bowel cancer.
- Providing soluble fibre which can help to reduce cholesterol levels.
Sources: There are two types of dietary fibre – insoluble and soluble.
- Insoluble fibre passes through the body mostly unchanged as it is undigested. It absorbs water and swells, resulting in a bulkier stool. This can be found in wholegrain foods, brown rice, wheat bran, fruit and vegetables peels and skins, nuts and seeds.
- Soluble fibre slows down the digestion and absorption of carbohydrates, so it helps to control blood sugar levels, which helps to stop you feeling hungry. Some research suggests that soluble fibre can reduce the blood cholesterol levels. This can be found in oats, nuts, legumes (peas, beans, lentils), fruits such as prunes, bananas and apples, vegetables such as potatoes, broccoli and carrots.
Excess and deficiency: A diet rich in cereals can reduce the body’s ability to absorb iron and calcium. The cereal can bind with the minerals making them less likely to be absorbed in the intestines. A deficiency of dietary fibre can contribute towards constipation and this could lead to an increased risk of bowel cancer.
Dietary reference values for fibre: SACN (Scientific Advisory Committee on Nutrition) recommends that the Dietary Reference Value (DRV) for dietary fibre is 30g for adults. Children should eat less because of their small body size. Very young children should avoid too many fibre-rich foods as being full up with fibre can it make it difficult for them to meet their other nutritional needs.