Harmful fungal toxins spreading in wheat

Fusarium head wilt infected wheat

Wheat infected with Fusarium head blight: a growing problem in Europe. Credit: University of Bath

Harmful fungal toxins are increasing in wheat crops in Europe, with nearly half of crops affected, a new study by the University of Bath in the UK has found.

Wheat, the most widely grown crop in the world, faces a growing threat from harmful toxins. A study led by Dr Neil Brown, a fungal biologist from the University of Bath in the UK and in collaboration with colleagues from the University of Exeter, found that almost half of wheat crops in Europe are affected by a fungal infection which leads to the production of these toxins.

The fungus that causes Fusarium head blight, a disease affecting wheat and other cereals in the field, produces mycotoxins that cause problems. These mycotoxins, when present in contaminated food products, can cause illness in humans and livestock, including vomiting and gastrointestinal problems. Additionally, mycotoxins can have a negative impact on farmers and the economy as they can decrease the value of the grain.

Wheat plays a huge role in the diet of mankind, providing 18% of the total calories in people’s diets around the world. Concerns for both our health and the global food supply were the drivers behind the new study.

Dr Brown, who works at the Milner Center for Evolution in the Department of Life Sciences in Bath, said: ‘Contaminated cultures and Fusarium toxins are always of concern as they pose a significant threat to our health, especially more than we only partially understand their effects on our well-being.

«But on top of these health issues, we need to remember that wheat is a hugely important global crop, so it’s critical for us to maintain high yields as well as safe food production – not least because of climate change, and now from the war in Ukraine (the world’s fourth largest wheat exporter), are already having an impact on wheat yields and grain prices.”

Preventing toxin contamination is therefore important both to help maintain wheat price stability and to protect our food security, ensuring global stability.

Fungal toxins found in nearly half of wheat

The research team reviewed the largest datasets available from governments and agribusiness, both of which monitor Fusarium mycotoxins in wheat grains entering our food and animal supply chains. Using data from across Europe (including the UK) from the past 10 years, the team has built the most comprehensive picture to date of the mycotoxin threat and how it is evolving.

Fusarium mycotoxins have been discovered in all European countries. Half of the wheat intended for human consumption in Europe contains the mycotoxin Fusarium “DON” (commonly called vomitoxin) while in the United Kingdom, 70% of wheat is contaminated. Governments set legal limits on the levels of DON contamination in wheat intended for human consumption. These regulations provide effective protection, with 95% of wheat intended for the table respecting the safety limits for DON concentration. However, the finding that mycotoxins are ubiquitous is concerning, as the effect of constant, low-level exposure to mycotoxins in our diet over a lifetime is not known.

«There are real concerns about the impact of chronic dietary exposure to these mycotoxins on human health,» Dr Brown said.

The high cost of toxins

When mycotoxins reach a certain level, contaminated grain is diverted from human food to animal feed. “It comes at a cost to the grain farmer, impacts grain market prices and shifts the health issue to our livestock,” Dr Brown said.

Therefore, the team found worryingly high levels of mycotoxin DON in wheat fed to cattle.

Ms. Louise Johns, Ph.D. student in Dr. Brown’s group said: ‘It’s much higher than in human food. This is an animal health concern, but it also paints a picture of what mycotoxin levels in food wheat could look like without current regulations.

For the first time, the Bath team has put a price tag on the impact of Fusarium Head Blight mycotoxins by estimating the value lost due to wheat being too contaminated with DON for human consumption.

“Across Europe, we estimate that 75 million tonnes of wheat (5% food wheat) exceeded the authorized limit for human consumption between 2010 and 2019. The downgrade in animal feed is equivalent to a loss of around 3,000 million euros over the last ten years. said Ms. Johns.

Interacting toxins

Alarmingly, the researchers found that 25% of food wheat containing the mycotoxin DON also contained other Fusarium toxins. And that’s probably an underestimate because not all wheat is routinely tested for other toxins. This means that other potentially harmful toxins are likely to fly under the radar. It is possible that these toxins interact synergistically with DON to have adverse health effects greater than a toxin acting alone.

Dr Brown said: ‘We don’t understand the health implications of being exposed to multiple toxins at the same time, especially when that exposure is chronic. We are concerned about increasing levels of co-contamination and possible synergies between toxins.

Growing threat

Fusarium head blight is a disease that fluctuates from year to year, but the authors of this study found that in the Mediterranean, mycotoxin levels in high disease years have become more severe since 2010. Here, the levels of mycotoxins recorded during the 2018 and 2019 outbreaks were higher than at any other time in the decade.

«We don’t know what is causing the increase in Fusarium mycotoxins, which is why we need more research, but we suspect that changes in agriculture (such as soil conservation practices that harbor the Fusarium fungus ) and climate change (such as warmer, more humid weather which favors the fungus Fusarium) play a significant role,” Ms Johns said.

Study co-author Professor Dan Bebber from the University of Exeter’s Department of Biosciences added: «It is essential that we have better systems to monitor the development of Fusarium head blight. on the ground and to predict which environments are most at risk in the future. ”


The team hopes that by exposing the magnitude of the Fusarium mycotoxin problem, their study will highlight the importance of mycotoxin control and stimulate further research.

Professor Sarah Gurr, chair of food safety at the University of Exeter, said: “We need to be vigilant in testing for mycotoxins in cereals. We each consume around 66 kg of wheat flour per year – for example, in pasta and bread – and it is important that the wheat is protected from Fusarium infection in order to mitigate this risk.

Dr Brown believes that developing better ways to protect crops from fungal pathogens «is the only way we can successfully mitigate the negative economic and health impacts of mycotoxins».

He said: «As mycotoxin outbreaks become more severe in the future with climate change, this problem will only become more significant.»

Reference: “Emerging Health Threat and Cost of Fusarium mycotoxins in European wheat” by Louise E. Johns, Daniel P. Bebber, Sarah J. Gurr and Neil A. Brown, December 15, 2022, natural food.
DOI: 10.1038/s43016-022-00655-z

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