Health assessment of dietary fibre

The term dietary fibre covers many very different food ingredients that are characterised by a common property: they are not or only incompletely broken down by human digestive enzymes as they pass through the mouth, stomach and intestines and are not absorbed. In the large intestine, some dietary fibres are metabolised by bacteria, for which they serve as a food source. Other dietary fibres are excreted undigested. Most dietary fibres in the human diet come from plant-based foods such as grains, vegetables or legumes (e.g. cellulose, hemicellulose, pectins, lignin, inulin). In addition, dietary fibres are also found in algae, fungi, bacteria and animal products or are obtained synthetically (modified carbohydrates).
 

Depending on their type and structure, dietary fibres can have different effects:

• they alter the time food spends in the gastrointestinal tract
• they influence the intestinal flora
   
• They reduce the reabsorption of bile acids and cholesterol absorption (influencing blood cholesterol levels)
• They delay glucose absorption (influencing blood sugar levels and insulin secretion) and fat absorption
• They bind toxic substances and minerals
   
• they increase the stool volume and the stool water content

Some dietary fibres, called prebiotics, are deliberately added to foods (enriched) or offered in the form of food supplements. The best known of these dietary fibres include inulin, oligofructose and lactulose.

The BfRshort forGerman Federal Institute for Risk Assessment carries out health assessments of dietary fibres.