Genome-edited wheat to reduce cancer risk from toast

Photograph of fresh toast bread jumping out of the toaster.

UK scientists have used genome editing to reduce a cancer-causing compound commonly found in toast.

Acrylamide forms during bread baking and its presence is further increased when bread is toasted, and the darker the toast, the more of this carcinogenic compound it contains.

A team has used the new technique of genome editing to develop a type of wheat that is less likely to produce acrylamide when baked (Wiley Online Library website).

The team is led by Biotechnology and Biological Sciences Research Council-funded Rothamsted Research with colleagues from the University of Bristol.

Trial of genome edited wheat

According to project leader, Professor Nigel Halford, the researchers are preparing an application to the UK government to run a field trial of this new wheat, starting in the autumn.

This will be the first such trial of genome edited wheat to be carried out anywhere in Europe.

The amount of acrylamide in bread is relatively low, but it increases many-times over when the bread is toasted.

What is more, the compounds that impart colour, flavour and aroma form by similar chemical pathways, so the darker and tastier the toast, the more acrylamide it is likely to contain. The same applies to other foods that are affected.

Reports on acrylamide

Acrylamide is classed as a probable carcinogen by the International Agency for Research on Cancer.

In 2006, a report stated that the potential cancer-causing effects of acrylamide in the diet were a concern. The report was from a United Nations Food and Agriculture Organization or World Health Organization Joint Expert Committee on food additives.

A similar conclusion was arrived at by the European Food Safety Authority’s Panel on Contaminants in the Food Chain (CONTAM) Committee in 2015.

This led to the adoption of a European Commission Regulation, which states that ‘acrylamide in food potentially increases the risk of developing cancer for consumers in all age groups’.

Genome editing

These serious concerns have led Raffan, Halford and colleagues to attempt to produce low asparagine wheat using genome editing.

The clusters of regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) genome editing technique leads to small changes in the DNA.

For example, the deletion or insertion of short sections of DNA, or changes to the DNA sequence. In this instance halting the function of a gene involved in the production of asparagine.

It differs from the genetically modified (GM) approach in that it doesn’t involve the introduction of novel, foreign or additional genes. The sorts of changes to the wheat DNA are similar to those that occur naturally: the power of CRISPR/Cas9 is that the changes can be directed to a specific target gene.

Genome edited plants

Despite the differences between genome editing with CRISPR/Cas9 and GM, genome edited plants are currently treated in the same way as GM under EU regulations. These are essentially blocking the use of a technology that is gaining official approval in many other parts of the world.

In this study, the researchers ‘knocked out’ the asparagine synthetase gene, TaASN2 (triticum aestivum asparagine synthetase 2), in wheat. Asparagine concentrations in the grain were substantially reduced in the genome edited plants compared to un-edited plants, with one line showing a more than 90% reduction.

Acrylamide only forms at high temperatures, and is associated with fried, baked, roasted and toasted foods. Alongside cereal-based products, these also include chips, crisps, roast potatoes and coffee.

Toast or roast to light brown

Project leader, Professor Nigel Halford said:

Acrylamide has been a very serious problem for food manufacturers since being discovered in food in 2002. It causes cancer in rodents and is considered ‘probably carcinogenic’ for humans.

It doesn’t just occur in toast and other wheat products, but many other foods that are fried, baked, roasted or toasted, including crisps and other snacks, chips, roast potatoes and coffee.

He added the following advice for consumers worried about the issue of acrylamide on their plate:

The colours associated with fried, baked, roasted and toasted foods form by similar chemical pathways to acrylamide, so colour is a very good indicator of how much acrylamide is forming. So, toast your bread or roast your potatoes to a light brown rather than dark brown colour.

Reducing the amount of asparagine

Sarah Raffan, who has just completed a PhD project to make and analyse the low asparagine wheat and who will be the lead researcher on the field trial said:

We’ve used genome editing to reduce the amount of the amino acid, asparagine, in the grain. It’s the asparagine that is converted to acrylamide during baking and toasting, so a low asparagine wheat should lead to lower levels of acrylamide, which is good news for anyone who likes their toast well done.

Top image:  Credit: ThomasVogel/Getty Images

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