A compound in carrots may reduce the risk of developing cancer, research suggests.
Carrots contain a beneficial natural pesticide
A team from the University of Newcastle Upon Tyne found the natural pesticide falcarinol reduced the risk of cancer developing in rats by a third.
They hope the discovery will lead to a new generation of anti-cancer drugs - and tips to growers on how to boost the beneficial properties of their produce.
Details are published in the Journal of Agricultural and Food Chemistry.
Falcarinol protects carrots from fungal diseases, such as liquorice rot that causes black spots on the roots during storage.
The scientists investigated the compound after a previous published study suggested it could prevent the development of cancer.
The research team carried out tests on 24 rats with pre-cancerous tumours.
After 18 weeks, rats who ate carrots along with their ordinary feed, and those given feed and falcarinol supplement were one third less likely to develop full-scale tumours than rats who were given just ordinary feed.
Researcher Dr Kirsten Brandt said: "We already know that carrots are good for us and can reduce the risk of cancer but until now we have not known which element of the vegetable has these special properties.
"We now need to take it a step further by finding out how much falcarinol is needed to prevent the development of cancer and if certain types of carrot are better than others, as there are many varieties in existence, of different shapes, colours and sizes.
"We could also expand our research to include other vegetables.
"For consumers, it may soon no longer be a case of advising them to eat five portions of fruit and vegetables per day but to eat particular types of these in certain quantities.
"The research could also lead to more tailored advice for growers regarding the methods they should use when growing vegetables."
The experiment was conducted using raw carrots so researchers do not yet know if eating boiled carrots or drinking carrot juice would have the same effect.
Dr Brandt recommended consumers should eat one small carrot every day, together with other vegetables and fruits.
Falcarinol is toxic in large amounts - but to obtain a lethal dose you would have to eat 400 kilograms of carrots at once.
Researchers suspect it stimulates mechanisms in the body that fight cancer.
Hazel Nunn, of Cancer Research UK, said there was plenty of evidence that eating fruit and vegetables can reduce your risk of cancer - but the reasons why were still unclear.
"People shouldn't think that eating a carrot a day will negate the effects of a diet of burgers and chocolate.
"To reduce your risk of cancer and other serious diseases our advice remains to eat at least five portions of different fruits and vegetables each day as part of a healthy and balanced diet."