Cereals and other fibres, definition, dietary recommendations, health effects and new perspectives

Jan Willem (right) awarded excellent presentation

Jan-Willem van der Kamp, TNO Food and Nutrition, The Netherlands 

Definition

In the past years agreement on implementation into practice of the Codex and similar-to-Codex definitions of dietary fibre has increased worldwide, including the inclusion of fibre oligosaccharides with DP 3-9, which are not measured in the classical analytical AOAC methods  1985.29. and 991.43. For food composition databases it is recommended  to list in addition to total fibre also both high MW fibre, as measured with the classical AOAC methods, and low MW fibre.

Dietary recommendations and health effects

Dietary recommendations of national and international authoritative bodies range from at least 25g to 40g fibre per day for adults. Most dietary guidelines prefer consumption of fibre naturally present in foods - fruits, vegetables and wholegrain products. These include both fibres and other bioactive co-passengers and it is not known whether purified added fibres convey similar health benefits. However, in recent years both naturally present fibres (e.g. bran) and some isolated fibres have got approved health claims. Research also shows that different fibres, and even differences in molecular weight of the same fibre, can have different effects on health. Current recommendations emphasise intake of cereal fibres, since these show more convincing associations than fibres from vegetables and fruits with long term health benefits such as reduced risks for diseases (e.g. heart diseases, type-2 diabetes, colon cancer) and lower over-all mortality. Recent research shows that, in addition to promotion of good laxation, consumption of cereal fibres also produce other beneficial short term effects, including improvement of psychological wellbeing.

New perspectives – the impact of fibre on the human gut microbiome

The benefits of dietary fibre consumption can be classified in small intestinal and large intestinal effects. Fibre-rich foods/meals, especially those increasing small intestinal viscosity can have important effects on blood glucose levels and appetite. An emerging area of great interest is the role of large intestinal bacteria  for health and wellbeing. More than a decade ago prebiotic, mostly oligosaccharidic fibres, such as inulins and ‘AXOS’, arabinoxylan oligosaccharides from wheat, were identified as agents promoting the growth of beneficial bifidobacteria. As is now revealed with new high speed genomic analytical techniques, the overall picture is highly complex and we are just starting to get some understanding. The number of bacterial cells in our colon is 10 times larger than the number of cells of our body and only 20% of the many bacterial species can be obtained and studied in culture. The unique, stable, rich and diverse microbiota composition of healthy subjects when destabilized (and reduced in diversity), can results in dysbiosis, causing weakening and leaking of the gut cell wall and a range of negative effects such as inflammation, a weakened immune system and obesity. There is a growing body of evidence that many types of fibre and high fibre foods, including those of (whole) grains and bran, can correct dysbiosis. However, more evidence is needed for getting – at least in Europe - approved health claims. The presentation will highlight the approach and cereal grain related results of the major MyNewGut EU project, investigating the influence of the microbiome on energy balance aiming at tackling diet-related diseases and behavior and at providing a stronger basis for health claims and dietary recommendations.

Conclusions 

Currently a diet high in total fibre and cereal fibre is recommended for health. In the next decade new insights will emerge in the role of the composition gut microbiome for enhancing health, and in the role of different fibres for modulating the microbiome composition. These new insights will also cover aspects of health and wellbeing not considered at present in recommendations.