The best thing since sliced bread? “High fiber white bread could be in supermarkets within five years,” say researchers

06 Feb 2020 --- A high fiber white bread could be available by 2025. That is according to an international group of scientists led by Rothamsted Research and the John Innes Centre, in the UK, who have successfully opened the door to healthier white bread, after they pinpointed genes responsible for the dietary fiber content of flour. The high fiber white flour has as much as twice the fiber of traditional white flour, the researchers claim.

The researchers 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, lead author Dr. Alison Lovegrove, Rothamsted Research, says the team achieved the breakthrough by exploiting the results of an earlier genetic screen of over 150 different wheat varieties from around the world.

Wheat breeding challenges
“It takes a long time to breed wheat conventionally and the wheat breeder will need to cross in the desired new trait (high fiber) into his current high yielding disease resistant wheat line and ensure that the offspring show the desired trait in the succeeding generations,” Dr. Lovegrove details.

“The new marker will help breeders to do this more quickly, but they still need to be sure that the trait is stable and then select only those lines that show the desired trait in later generations. When they have got the wheat line with high fiber they then need sufficient seed to do national field trials around the country, so that it can be evaluated by other growers before it can become a new ‘variety.’ So, this would take a minimum of five years,” she tells FoodIngredientsFirst. 

“The white flour used in so many bakery products could be healthier with this new breakthrough,” Dr. Lovegrove continues. “Our hope would be that there would be no extra cost to the consumer and they wouldn’t have to change their eating habits.”

“We knew that the white flour made from one particular Chinese wheat variety, Yumai 34, was unusually high in fiber, but it’s not well suited for growing in European climates,” she says.

“Using conventional breeding techniques, we crossed this high fiber trait into several other varieties. This allowed us to narrow down where in its genome the genes for high fiber are.”

Traditionally, crop varieties are improved by identifying plants with desirable traits and breeding from them. The problem with high fiber 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 fiber genes,” explains Dr. Lovegrove.

That will allow them to incorporate the high fiber into elite wheat lines – and opens the possibility of significant increases in dietary fiber intake for everyone, she adds.

A quest in increasing fiber content
The quest to increase fiber in white bread through breeding had stalled in recent years – with various manufacturers instead producing loaves that contain both white and wholemeal flours, or have fiber from other sources added, in an attempt to address the issue.

“We hope to go on and identify further genes that increase fiber content, thereby providing plant breeders, millers and food producers with even more options,” Dr. Lovegrove states. The effort behind the study was no simple matter, however, as the wheat genome is much bigger than the human genome – containing six copies of every chromosome rather than the two copies humans possess. 

This means wheat has in the region of 150,000 genes, compared to about 25,000 genes in humans.

By looking for sections of genetic code shared by plants with the high fiber trait, the team were able to hone in on the likely spots where high fiber genes reside.

The researchers found two sites in particular – on chromosomes 1B and 6B – that were strongly linked with high fiber in flour.

The conventional breeding of a new wheat variety is a slow process with breeders having to select wheat lines with high yield and disease resistance, but the team is hopeful high fiber bread and other products made from white flour will be a staple within just five years now that breeders have a new tool with which to screen wheat lines.

Dietary fiber describes the carbohydrates from plant-based foods that aren’t digested in the small intestine and has been shown to have a number of health benefits, including lowering blood pressure, improving insulin sensitivity and reducing the incidence of certain types of cancer.

Although the mechanisms are incompletely understood they include a reduction in the time taken for food to pass through the intestines; binding cholesterol and carcinogens; promoting the growth of healthy bacteria in the gut; and reducing the rate of both digestion and glucose release in the small intestine. 

Most of the fiber found in wheat grain is in the bran – the part that is removed when producing white flour and what differentiates it from wholemeal flour.

Fiber consumption figures down in UK
The dietary recommendations for fiber consumption in the UK are 30 g per day, but British consumers are only eating around 15-18 g per day, according to Dr. Lovegrove. This is also generally reflected around the world with a significant amount of people not getting their daily recommended fiber dose. 

“We already get about 40 percent of the fiber in our diet from cereals and about half of that from bread [about 10 percent from white bread]. So, if we can, for example, double the level of dietary fiber in white bread we would hope to have a very positive impact on the health of the general population,” she reveals. 

A slice of typical white bread has about 1 g of fiber, whereas wholemeal has about 3 g. A slice from a high fiber white loaf could contain up to 2 g.

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.

Taste, appearance, shelf life and price are the main reasons why consumers favor white bread, while the £8 billion (US$10.3 billion) a year pre-packed sandwich industry prefers it as it refrigerates better. 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 program – along with colleagues in Hungary, France and Turkey.

By Elizabeth Green