Wheat is healthy and can get healthier
The first study compares historic and modern wheat varieties grown side by side has shown an increase in dietary fibre and other features beneficial to human health. This is contrary to concerns that the push for higher yields has made today’s wheat less “healthy” than older types.
The 39 wheats varieties, spanning a period of 230 years, were grown three years running at Rothamsted Research in Hertfordshire – which is also the site of the famous Broadbalk wheat trial, which was established in 1843 and is the world’s longest running experiment.
Lead author Dr Alison Lovegrove said: “Despite concerns over the declining genetic variation found across modern wheat types, there is no evidence that the health benefits of white flour from wheat grown in the UK have declined significantly over the past 200 years.
“In fact, we found increasing trends in several components, notably the major form of dietary fibre. This is despite great increases in the yields of wheat grown over this period.”
The team also found the concentration of betaine, which is beneficial for cardio-vascular health, has increased, whilst levels of asparagine - which can be converted to the potentially cancer-causing chemical acrylamide when bread is baked - have decreased.
The amount of certain sugars, including sucrose, maltose and fructose, have also increased over this period.
For the purposes of the analysis, 39 wheats were split into three groups – nine which were bred in the years 1790-1916, before an understanding of genetics had been developed; 13 varieties came from 1935-1972, recognised as a period of increasing scientific understanding; and 17 cultivars that were bred using modern breeding techniques between the years 1980 and 2012.
After milling the grain to white flour, the researchers found that the content of dietary fibre has increased steadily over the past two centuries, with modern varieties containing, on average, about a third higher concentration of the major fibre component, the cell wall polysaccharide, arabinoxylan.
This may be significant for consumers, because fibre is deficient in UK diets with about 10% of the intake coming from white bread.
However, a second study shows we can improve on that. It has pinpointed the genes responsible for the dietary fibre content of flour to create a new variety of white flour with twice the fibre.
The team say this new white flour is otherwise identical and makes a good quality white loaf – but with all the added health benefits that come from eating wholemeal bread, including reduced cancer, diabetes and obesity risks.
Writing in the journal PLOS ONE, Dr Lovegrove (also the lead author on this paper), said the team had achieved the breakthrough by exploiting the results of an earlier genetic screen of over 150 different wheat varieties from around the world.
“We knew that the white flour made from one particular Chinese wheat variety, Yumai 34, was unusually high in fibre, but it’s not well suited for growing in the European climate,” she said.
“Using conventional breeding techniques, we crossed this high fibre trait into several other varieties. This allowed us to narrow down where in its genome the genes for high fibre are.”
Traditionally, crop varieties are improved by identifying plants with desirable traits and breeding from them. The problem with high fibre is it is not a trait you can identify by eye – and biochemical lab tests for it are slow and expensive.
“We’ve developed genetic markers that can easily be used by plant breeders to identify which individual wheat plants have the high fibre genes,” said Dr Lovegrove.
That will allow them to incorporate the high fibre into elite wheat lines - and opens the possibility of significant increases in dietary fibre intake for everyone, she added.
A slice of typical white bread has about 1g of fibre, whereas wholemeal has about 3g. A slice from a high fibre white loaf could contain up to 2g.
Whilst wholemeal is widely regarded as being much better for us, white bread still outsells it, making up three quarters of the roughly 12 million loaves sold in the UK each day.
This study was a collaborative project with researchers from Rothamsted, the John Innes Centre and the University of Bristol in the UK - who are all part of the BBSRC funded Designing Future Wheat programme – along with colleagues in Hungary, France and Turkey.
The project was funded by UKRI BBSRC and also involved staff from the University of Bristol.