The health of UK consumers can be improved by increasing the content of dietary fibre in white flour, according to PETER SHEWRY, ALISON LOVEGROVE (Rothamsted Research) and SIMON GRIFFITHS (John Innes Centre)
Wheat has been central to the debate about the relationship between food and health, with negative views expressed about the role of bread and other wheat-based foods in promoting weight gain and of gluten in triggering allergies and intolerances.
However, these negative views are based largely on anecdotal reports and driven by the social media and popular press, with little established scientific evidence.
Furthermore, they ignore the scientifically established contributions of wheat to nutrition and health, as a provider of protein, B vitamins, minerals and, in particular, dietary fibre.
Dietary fibre is essential for human health and, apart from a small contribution from fungi, derived only from plant foods. Fibre has a range of health benefits and the consumption of fibre-rich foods is associated with decreased risk of chronic diseases (notably cardio-vascular disease and type 2 diabetes) and some types of cancer (notably colorectal cancer).
These established associations between fibre intake and heath have led the NHS to recommend a daily intake of 30g of fibre a day, but most individuals fall far short of this with the average intake being about 18g.
Bread is an important source of fibre in the UK diet, providing about 20% of the daily intake. However, only half of this comes from the consumption of white bread, which contains less than 5% fibre compared with up to 15% in the whole wheat grain and products made from wholegrain flour.
Consequently, much of our knowledge on the association between fibre intake and health outcomes is based on studies of wholegrain consumption.
However, the higher cost and limited consumer acceptability of wholegrain products limits our ability to deliver health benefits by increasing the consumption of wheat grain fibre.
Although wholegrain products have been widely promoted, backed by health claims accepted by the US FDA and EU EFSA, this has failed to have a significant impact on their consumption in the UK, which is consistent with other studies which show that populations are resistant to large scale changes in diet.
We therefore consider that a more realistic strategy is to increase the content of dietary fibre in white flour and bread. Furthermore, we think that this can be achieved without affecting the cost, processing quality or consumer acceptability.
Our research on wheat fibre started in 2005 when we joined the HEALTHGRAIN project funded by the EU. Although this project focused on increasing the consumption of wholegrain, we also studied white flour, showing wide variation in the concentration of dietary fibre, and particularly of the major dietary fibre components, a cell wall polysaccharide called arabinoxylan (AX) which accounted for between 1.35 and 2.75% of the flour dry weight.
The identification of this variation allowed us to take a classical genetic approach to increasing AX content in white flour, by identifying high fibre variants of genes that control AX amount. We have so far identified two such variants, in high fibre lines from China (Yumai 34) and France (Valoris), and have crossed them with UK wheat cultivars to develop prebreeding lines
These lines the basis for a new LINK project which is supported at Rothamsted Research and the John Innes Centre by the BBSRC and eight UK industry partners: four wheat breeding companies, two milling and baking companies, the Federation of Bakers and UK Flour Millers.
The aim of this four-year project is to develop new high fibre cultivars suitable for commercial production in the UK, and to establish whether their use will require any changes in the conditions used by millers and bakers. The first year of field experiments is underway and we will be reporting on the progress of the project in future bulletins.