Carbohydrates and dietary fibre

The health benefits of including sufficient dietary fibre in the diet have been well described and have formed the basis of dietary recommendations around the world. However, dietary fibre is a complex dietary entity, consisting of many non-digestible components of food. Debate surrounding the definition and measurement of dietary fibre has resulted in inconsistencies in labelling, description and recommendations set across the world. In the UK, dietary recommendations are made using the fraction of non-digestible material described as non-starch polysaccharide that is measured by the Englyst method. However, the Association of Official Analytical Chemists (AOAC) methods, used widely by the food industry, capture a much greater range of non-digestible material, that some suggest should be included in any definition of dietary fibre. An attempt to resolve such discrepancies, possibly by taking an approach that considers the health effects of fractions not captured in the Englyst method, is probably overdue. Additionally, it is clear that the effects of these various non-digestible components of dietary fibre are not interchangeable, and it is important that fibre comes from a range of sources to ensure maximum health benefits from the fibre in the diet. Traditional 'insoluble' fibres are required to add bulk as well as rapidly fermentable, viscous fibres to bring about cholesterol lowering. There is also a convincing argument for including slowly fermented components, such as resistant starches, that are well tolerated in the digestive system and can bring about improvements in gut function. Currently there is insufficient data from well designed human intervention trials to make specific recommendations on the amounts of these fibre components in the diet, but it may be useful for health professionals to talk in terms of the different food sources of these types of fibre, as well as total fibre amounts.