Dietary fibre

Human Nutrition 3(3+0)
Lesson 13 : Carbohydrates

Dietary fibre

Dietary fibre is primarily a polysaccharide that differs from starch in the linkage between the sugar units. Even after cooking, these links cannot be digested by the human enzymes in the small intestine. This prevents the absorption of sugars that make up the dietary fibre. Dietary fibre is not a single compound but a group of compounds with similar characteristics. The group consists of the carbohydrates cellulose, hemicelluloses, pectins, gums and mucilages as well as the non-carbohydrate lignins, which are alcohol derivatives.

Dietary fibre is classified as

  1. Insoluble dietary fibre – does not dissolve in water and do not get digested by bacteria in the large intestine example: cellulose, some hemicelluloses and lignins, and
  2. Soluble dietary fibre – fibre that either dissolve or swell in water and are metabolized by bacteria in the large intestine, these include pectins, gums, mucilages and some hemicelluloses.

A reasonable level of dietary fibre intake in the average Indian vegetarian diet is about 45-50 grams per day. This will help in controlling the blood cholesterol level and also in preventing the problem of colon cancer. Very high dietary fibre intake for example 75-80 grams per day can pose some health risks. A very high fibre intake requires a high water intake. Not consuming enough water with dietary fibre can leave the stool very hard, making it difficult and painful to eliminate. Large amount of dietary fibre can also bind some important minerals especially calcium, iron and zinc making them less available to the body.

Last modified: Wednesday, 8 February 2012, 7:28 AM