for a responsible, fair & sustainable food system

GM developer denies purple tomato health claims under pressure on the Today programme

Posted 5th February 2026 in News

A genetically modified purple tomato developed two decades ago in Norwich is once again in the news after regulatory approval in Australia. Radio 4 dedicated a few minutes of prime airtime on February 2 to the news. Our Executive Director, Leonie Nimmo, was live on the programme alongside GM developer Cathie Martin.

GM food can be sold in the UK but must undergo safety testing and be labelled. The developers plan to apply for UK approval for the tomato and, according to an article in The Times, they hope it will be a “vanguard product”, prising open the UK’s regulatory process for other GMOs to follow.

When the UK exited the European Union, we inherited regulations that require a 90-day rodent feeding study of GMOs to test their safety. It seems likely that the GM tomato developers will lobby for a change in the law so that this expensive and ethically problematic requirement is abandoned. Presumably they consider the time to be more politically favourable now than at any other point in the mutant tomato’s long history.

Are they healthy?

The tomatoes have been genetically modified to contain high levels of anthocyanins, which have been claimed to be antioxidants.

In 2008, Martin and colleagues conducted feeding trials of the tomatoes on some genetically-modified, cancer-prone mice. A press release from the John Innes Centre, where the tomatoes were developed, announced “Purple tomatoes may keep cancer at bay”. News outlets duly repeated the claims, while the Express ditched all qualifications, declaring “Purple tomato can beat cancer”.

The NHS was unconvinced. “This study cannot determine what role these GM tomatoes might play in preventing disease in humans,” it concluded, highlighting the very small sample size of just 20 mice used in the experiment. Indeed, the scientists themselves described the study as a “pilot”, indicating that further tests were required. Cancer Research UK also urged caution, referencing the lifestyle and genetic influencers of cancer and the danger of claims that “high-tech fruit and veg” can compensate for such factors.

Speaking on Radio 4, Leonie highlighted the historical unsubstantiated health claims and the response of cancer authorities. Remarkably, Martin denied that they (the developers) had ever made any health claims. This may be because, according to UK rules, “You cannot claim or imply that food can treat, prevent or cure any disease or medical condition”.

GM Freeze wonders whether Martin’s quote from the 2008 JIC press release had been seen by a lawyer. It read: “This is one of the first examples of metabolic engineering that offers the potential to promote health through diet by reducing the impact of chronic disease.”

But 17 years after the ‘pilot’ study, there is one health claim that Martin is sticking to: anthocyanins are “very good antioxidants”, she told the Today programme. However, even this does not appear to be a permissible claim according to several entries in the UK’s Health Claims Register, which relate to foods containing naturally-occurring anthocyanins. It references a scientific opinion of the European Food Safety Authority, which states that “a cause and effect relationship has not been established between the consumption of the food(s)… and a beneficial physiological effect related to antioxidant activity, antioxidant content, or antioxidant properties”.

Furthermore, Cancer Research UK challenged the over-simplistic assertion that antioxidants prevent disease. It is “not what the science says”, it reported.

Are they safe?

In 2008, the NHS stated that, until the tomatoes are tested on humans, it won’t be clear whether there will be any unexpected harms.

When Martin’s purple tomatoes received regulatory approval in the USA in 2024, GM Freeze raised questions over the level of anthocyanins that Martin’s mutant tomatoes contain. As non-essential nutrients, there are no recommended daily amounts for anthocyanins, nor are there recommendations on toxicity levels.

Claire Robinson, editor of GM Watch, notes that the anthocyanin level in the tomatoes is “extremely high”, and is concerned that this might present a danger to health. Research indicates that overloading with antioxidants can damage organs and cause harmful changes in hormones and thyroid function, she says.[i]

Naturally-occurring anthocyanins are found in fruits including blackberries, blueberries and pomegranates. These are not consumed in the same quantities as tomatoes, which we eat not only fresh but also in sauces and processed foods. Furthermore, Martin and colleagues have created a fruit that has anthocyanins at quantities far in excess of what occurs in fruit naturally. Such concentrations may be present in supplements rather than fresh fruit, so should Martin’s tomatoes be regulated as such?

For Robinson, another major issue is that the biochemical pathways in the plants have been changed. “Plants very easily can become toxic––even non-GM plants. They do it in response to pests and diseases,” says Robinson. “We don’t know what the new genes are going to do in the tomatoes.”

Robinson calls for whole genome sequencing and detailed molecular analysis of the tomatoes, to check for toxins, allergens and unexpected changes.

Past their best

Another worrying issue with the GM tomatoes is that they are designed to last longer. Tests show a longevity of 48 days from harvest compared to 21 days for conventional tomatoes, according to The Times. This means that they are less likely to go mouldy––a recurring claimed benefit of a number of GMOs.

But who wants to eat food that would otherwise be rotting, and what does the prolonged shelf-life do to all the nutrients we would expect to find in a tomato? Vitamin C has been found to degrade rapidly after harvesting, and tomatoes are an important source.

Public costs, privatised benefits

The John Innes Centre is a research institute that received over £44 million in public money in 2024––more than 75% of its income. The cost of the purple tomato development and how much of that bill was footed by taxpayers is unclear. In 2008, developers Cathie Martin and Jonathan Jones from the JIC formed the private company Norfolk Plant Sciences to commercialise their products. In the USA, their purple tomato business is run by a subsidiary, Norfolk Healthy Produce (NHP).

Enclosing the genetic commons

If Martin and Co. are not allowed to make any health claims about their GMO tomatoes, it does raise the question of what exactly is the point of them. Leonie described them as unnecessary, unwanted and unsafe, and noted environmental and socio-economic risks as well as health risks. She highlighted the crucial issue of patents, which lead to restrictions in traditional breeding. [ii]

This is not a theoretical issue for Cathie Martin. Hot on the heels of the GM tomato product launch in the USA, NHP filed a patent infringement lawsuit against a company that was selling purple tomato seeds it claimed were produced conventionally. According to the Baker Creek Heirloom Seed Company, tests of its tomato did not find evidence of NHP’s genetically modified material, but nor could it be proved that it was free of it. The Baker Creek tomato was withdrawn.

It would seem that the underlying business model for biotech companies is not that of selling seeds or food, but of breeding patents. This could have livelihood impacts for seed breeders and farmers and price impacts for consumers. It will also negatively impact biodiversity, in turn impacting our resilience and ability to adapt to climate change in the future.