[ad_1]
Examine, a free weekly newsletter covering science with a sceptical, evidence-based eye, is sent every Tuesday. You’re reading an excerpt – sign up to get the whole newsletter in your inbox.
Sporting a glossy complexion the colour of a royal velvet robe, genetically modified tomatoes spliced with genes from a snapdragon flower are coming to our greengrocers.
The snapdragon genes enrich tomatoes with natural compounds called anthocyanins, which could help prevent cancer and slow down cognitive decline. They also turn the fruit’s flesh deep violet.
After Australian regulators granted their approval last week, the purple tomatoes are poised to become the first genetically modified fresh food products available.
Appetite for the gene-tweaked fruit could act as a vital test case for whether more GM foods are sown in Australian soil.
How enthusiastically should we embrace purple bruschetta once the tomatoes go on sale later this year? Here’s what the science says.
What’s the big deal?
Genetically modified crops were once banned; NSW lifted an 18-year moratorium on growing GM crops as recently as 2021. A moratorium is still in place in Tasmania.
The bans and public suspicion towards GM foods were driven by some small and badly designed studies in the 1990s and early 2000s that reported eating GM foods could hurt health. The consensus nowadays is that GM foods are just as safe as crops tweaked through conventional breeding techniques.
Australian farmers can grow some GM crops but none are whole fruits or vegetables. There’s canola designed to withstand herbicide, for example, but because the heavily processed end product – in canola’s case, oil – doesn’t contain DNA, it isn’t labelled as GM food.
An Aussie-made banana edited with an antifungal gene was also approved last year. But the bananas won’t be grown until the deadly Panama fungus – which threatens to drive Cavendish bananas to extinction – takes hold in Australia.
The purple tomatoes, meanwhile, are slated to hit market shelves late this year and become the first fresh genetically modified whole food grown and sold in Australia.
Produce distributor All Aussie Farmers is bringing the fruit here through a commercial partnership with the UK company Norfolk Plant Sciences, which was founded by the scientists who created the tomatoes.
Travis Murphy, managing director of All Aussie Farmers, expects “Purple Bliss” to be popular. He aims to get the first punnets on sale at Melbourne fruit shops in spring.
What’s the evidence behind health claims?
The purple tomatoes are packed with anthocyanins, which are antioxidant compounds found in red and purple fruits and veggies including red cabbage, eggplant and cherries.
They’re part of a group of chemicals called flavonoids, which a growing body of evidence has linked to a raft of longevity-boosting effects including better brain and heart health.
Normal tomatoes don’t contain anthocyanins. But about 20 years ago, UK scientist Professor Cathie Martin found a way to ramp up the production of anthocyanins in tomatoes by introducing two genes from edible snapdragon plants.
Purple-skinned tomatoes already existed but Martin’s tomatoes have deep purple flesh all the way through and much higher levels of anthocyanins.
There’s a good amount of observational evidence that suggests the antioxidant and anti-inflammatory effect of anthocyanins could reduce risk of cardiovascular and neurodegenerative diseases. A study of 16,010 older women found those who ate the most anthocyanin-rich berries delayed cognitive ageing by 2½ years.
Anthocyanins have also been shown to disrupt the growth of bowel cancer and melanoma cells in mice. One experiment co-run by Martin involved mice genetically edited to be more prone to cancer. Some were fed the GM purple tomatoes, while the others ate the normal red variety. The mice who ate the purple tomatoes lived 30 per cent longer.
Systemic reviews, however, have noted there are scant randomised controlled trials (the gold standard of scientific evidence) on anthocyanins in humans, and although many researchers are encouraged by the existing evidence, most have called for more robust testing beyond animal experiments.
What do purple tomatoes taste like – and will we eat them?
Agronomy professor Daniel Tan at the University of Sydney visited the tomatoes’ inventor Martin in 2010 as she perfected the fruit at the UK’s John Innes Centre. He described her as a great scientist who didn’t act like a normal researcher; she scooted him around in a convertible sports car.
“They gave me a small piece and it tasted just like a normal tomato,” Tan recalls.
The tomatoes represent a shift from just using genetic engineering to protect crops against pests and disease to harnessing the technology to boost nutrition, he said.
“The purple tomato is an example of ‘next-generation’ GM foods, which are modified not just for protective genes but for potential consumer health benefits,” he says.
Tan said he expected some people to be anxious about eating a GM fruit.
Three decades ago, a rot-resistant GM tomato called the Flavr Savr hit the market in the US and totally flopped. “People just complained about it being genetically modified and a Frankenfood, that sort of thing,” Tan said.
Times have changed, but just under half of Australians maintain some level of concern about GM foods, according to a 2022 survey run by Food Standards Australia New Zealand, the regulator alongside the Office of the Gene Technology that green-ticked the purple tomato.
There are also plenty of non-GM alternatives for foods rich in anthocyanins, including blueberries (which still have higher concentrations than the purple tomatoes) and the high-antioxidant Queen Garnet plum.
Consumers’ reaction to the GM tomatoes would help gauge what kind of appetite there is for more GM foods in the future, Tan says.
Will we soon find the pink-fleshed pineapples and non-browning apples sold in other countries in our supermarkets? That question is, at least partly, down to the success of a purple tomato.
The Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.
Angus Dalton is the science reporter for The Sydney Morning Herald.Connect via X or email.From our partners
[ad_2]
