No evidence that modern types of wheat have lower quality for human nutrition and health, with the exception of decreased levels of some minerals (including iron, zinc and magnesium)

Do modern types of wheat have lower quality for human health? P. R. Shewry  K. L. Hassall  H. Grausgruber  A. A. M Andersson  A.‐M. Lampi  V. Piironen  M. Rakszegi  J. L. Ward  A. Lovegrove. Nutrition Bulletin, September 22 2020. https://doi.org/10.1111/nbu.12461

Abstract: Wheat is the major staple food in Western Europe and an important source of energy, protein, dietary fibre, minerals, B vitamins and phytochemicals. Plant breeders have been immensely successful in increasing yields to feed the growing global population. However, concerns have been expressed that the focus on increasing yield and processing quality has resulted in reduced contents of components that contribute to human health and increases in adverse reactions. We review the evidence for this, based largely on studies in our own laboratories of sets of wheats bred and grown between the 18th century and modern times. With the exception of decreased contents of mineral micronutrients, there is no clear evidence that intensive breeding has resulted in decreases in beneficial components or increases in proteins which trigger adverse responses. In fact, a recent study of historic and modern wheats from the UK showed increases in the contents of dietary fibre components and a decreased content of asparagine in white flour, indicating increased benefits for health.

Discussion

It is clear from the studies discussed above that intensive wheat breeding has resulted in increased accumulation of starch, which is generally associated with a decrease in the concentration of protein. Analysis of the Austrian Heritage lines also indicates that there have not been increases in proteins known to trigger adverse reactions. Other effects of breeding on grain composition are less clear, and the studies discussed in detail here demonstrate the challenges.

One major challenge is that grain composition is strongly affected by the environment (Shewry et al. 2010). Hence, it is essential to compare material grown in replicated multi‐environment field trials. Furthermore, the varieties compared should be adapted to the area of growth, to avoid the effects of environmental stress. The HEALTHGRAIN study clearly did not fulfil these criteria, and it is not surprising that few correlations were observed, and, with the exception of starch and protein, these were marginal in significance (accounting for between 2% and 5% of the variation observed in the analyses). Nevertheless, the analyses are of interest in that they show no major changes in composition.

By contrast, the UK Heritage Wheat samples were from replicated multi‐site trials with an emphasis on flour composition. Statistical analyses of these samples showed positive correlations of release date with the contents of arabinoxylan fibre (accounting for 21% of the total variation), total sugars (41%) and betaine (19%), and negative correlations with total amino acids (15%) and individual amino acids including asparagine (Lovegrove et al. 2020). These changes have clear implications for human health.

Wheat is the most important single source of dietary fibre in many diets, including the UK and Western Europe, and the increased content of arabinoxylan (the major fibre component) in white flour is certainly desirable. The decreased concentration of asparagine in modern wheats is also desirable as it reduces the potential for the formation of acrylamide during processing.

By contrast, the increases in fermentable monosaccharides, disaccharides and oligosaccharides (sucrose, mannitol, fructans) may be of concern to consumers suffering from irritable bowel syndrome (IBS), as these form part of the FODMAP fraction (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) that exacerbate IBS symptoms (Gibson & Shepherd 2010). However, wheat is already recognised as a major source of FODMAPs in the diet (Biesiekierski et al. 2011; Whelan et al. 2011) and excluded by many IBS patients.

To conclude, the analyses discussed provide no evidence that modern types of wheat have lower quality for human nutrition and health, with the exception of decreased levels of some minerals (including iron, zinc and magnesium) which are discussed elsewhere. In fact, there is evidence that they may be superior in some respects, particularly in fibre content of white flour. However, the analyses also show the challenges facing researchers and the need for more datasets from well‐designed field trials.