TABLE OF CONTENTS Fibre is not a nutrient in the same way as starch or protein: it does not provide energy and is not involved in energy metabolism at the cellular level. However, it does influence many digestive processes and so is included here to indicate its relevance to human nutrition. The functional fibre in our diet is derived from the macromolecular chemicals in plants (including algae and fungi such as the Quorn mycoprotein fungus) that contribute to its structure. The main characteristic of fibre from a dietary point of view is that it cannot be digested by human digestive enzymes, although some can be broken down by gut bacteria. Fibre plays a major role in for the maintenance of correct function in the gut. There is also evidence that certain types of fibre can affect the way that fat is transported in the bloodstream.
Most dietary fibre groups are polysaccharides of one type or another. Celluloses are the main constituent of plant cell walls, and therefore occur in all plant-containing foods. Hemicelluloses are a major constituent of cereal fibres; they are a very diverse group of chemicals, some of which are soluble. Pectins are widespread in vegetables and fruit, especially citrus fruits and apples. As well as being consumed as the normal constituents of these foods, they are widely used as ingredients by food manufacturers as thickeners and gelling agents. Gums are another group of dietary fibre chemicals that are widely used in the food industry as additives, having stabilizing...
