Possible implications for health of the different definitions of dietary fibre

There is impressive evidence from epidemiological and experimental studies that dietary fibre derived form vegetables, fruit and wholegrain cereals protects against and may be useful in the treatment of a wide range of diseases. However, while there is some evidence of benefit of extracted and synthetic fibres in terms of lowering levels of cardiovascular risk factors, improving measures of glycaemic control and gastrointestinal function, epidemiological confirmation of clinical benefit and long term safety are lacking. An appropriate definition of dietary fibre is essential, given that claiming a food is high in dietary fibre is in effect making a health claim, without formally doing so. The new Codex definition acknowledges the difference between naturally occurring carbohydrate polymers which are neither digested nor absorbed in the human small intestine and synthetic or extracted polymers. However the latter two groups may also be defined as dietary fibre provided “beneficial physiological effect has been demonstrated by generally accepted scientific evidence”. Given the need for a definition of dietary fibre which can be used for food labelling, setting nutrient reference values and decisions relating to health claims it is important to achieve agreement as to what constitutes a meaningful physiological effect and the level of evidence required to be certain of such effect.