Their cheerful orange colour has helped make them one of the world's most popular vegetables.

But the humble carrot is quickly changing colour - as a growing army of consumers switch to black and purple varieties, according to the Daily Mail.

Darker shades are increasingly being sold in grocers and restaurants across the UK as part of the drive to eat a "rainbow diet".

Full of antioxidants, darker carrots are reputed to help ward off cancer, reduce cholesterol and keep your heart healthy.

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Luke Caddel, of gourmet food company Fine Food Specialist, said the dark purple varieties were now even more popular than the orange carrots most of us grew up with.

He added: "Sales of black and purple carrots went up by 40 per cent last year. I think people are more open to new ingredients and there has been a huge focus on clean eating too.

"As well as warding off diseases, they are much sweeter and have a slightly different texture."

Dr Charlotte Allender, from the Genetics Resources Unit at Warwick University, said the world's very first carrots were in fact purple and black - but they died out as humans increasingly favoured the orange varieties. She added:"Black and purple carrots don't have as much beta carotene as the orange carrot, but are full of antioxidants.

"They are probably best very lightly cooked or raw to retain their colour."

Food expert Jane Milton also explained dark carrots' appeal. She said: "Darker-coloured fruits and vegetables are full of anthocyanin, which are powerful antioxidants."