For the ultimate in health-boosting superfoods, look towards the purple end of the spectrum

The three-course meal gum takes her on a culinary journey through tomato soup, roast beef and baked potato, before she meets an unfortunate end on the faulty blueberry pie flavour.

The spectacle of Violet transforming into a girl-sized blueberry should be enough to swear anyone off purple food for life. But in foodie circles, purple is fast becoming the new green - up until now the colour of vegetable most beloved by nutrition experts.

Earlier this month, Sainsbury's started selling Purple Majesty potatoes, which not only have a purple skin but also a deep, inky-coloured flesh.

Next month the red sprout will land on our shelves. "Fed up with getting your kids to eat greens?" the advert goes. "Try purples." The new variety of the vegetable is supposedly milder and sweeter than the bitter tasting green version. Ideal, then, for those who dread Brussels sprouts over the festive season.

But what of the old favourites? The purple sprouting broccoli, the beetroot, the aubergine, the grape, the blueberry, the red onion, and the purple asparagus, grown in Britain for the first time earlier this year, and which is so sweet it can be eaten raw? Purple legumes are fast becoming the "it" vegetables of the food world.

Beyond their rather pleasing appearance on the plate, deep purple and bluish foods are actually a cue for nutritional super powers.

In addition to lowering the risk of some cancers and heart disease, there is evidence that they can improve urinary tract health, memory function, and slow down the ageing process as well as offering a wealth of other benefits.

Their attributes have become so renowned they have even prompted an A-List slimming craze in the shape of The Purple Food Diet. Devotee Mariah Carey has gone on record to say that every time she wants to shed a few pounds for a red carpet event, nothing but purple food will pass her lips.

Potato producer Albert Bartlett, which has its headquarters in Airdrie, has been working with Queen Margaret University in Edinburgh and the Scottish Crop Research Institute to determine exactly what health benefits there could be from eating the new purple potato.

"Our research specifically looked at Purple Majesty potatoes which, unlike white potatoes, contain natural pigments called anthocyanins," says Dr Catherine Tsang, who took part in the research. "It's this pigment that gives the potato the purple appearance but, more importantly, it possesses antioxidant properties, even after cooking.

"Antioxidants are chemicals which help to reduce free radicals in the body. Free radicals have been linked to health problems such as heart disease and some cancers, and that's why antioxidants are essential in our diet because they can offer protection against disease.

"Approximately 80 per cent of the UK population consume potatoes on a daily basis. By switching from ordinary white potatoes to purple potatoes, people will have the potential to increase their antioxidant intake as part of a healthy balanced diet".

Those interested in benefiting from anthocyanins don't need to stick to purple potatoes though. These most potent of phytonutrients are present in almost all purple vegetables and fruit. Rather than being a new-fangled invention bred in a laboratory somewhere, in many cases they are actually bred by returning a vegetable to its natural form.

It may be hard to imagine carrots as anything other than orange but until the 17th century, they were a deep purple colour. The orange variety was bred by Dutch plant breeders as a symbol of the country's rebellion against Spain under William of Orange.

Purple cauliflowers have also been cultivated for centuries and are popular in Italy.

While purple veg may look strange, it certainly doesn't taste it, and in many cases it is easier on the palate than its more conventional cousins.

According to most experts, though, the most important thing to remember when incorporating purple food into your diet is balance.

"If there was a multi-coloured vegetable, with a spectrum of colours that all represented a different nutritional benefit, that is the one that I would be recommending," says Sarah Stelling, from Edinburgh Centre of Nutrition and Therapy. "In reality though, they all come separately, and we need to find creative ways to get them into our diets.

"Purple foods are extremely important and provide specific nutrients that you can't get from other vegetables, but they are not enough on their own. No vegetable is. Aim for a rainbow of colours and you will be on your way to being the healthiest you can be."

• This article was first published in the Scotland on Sunday on November 7, 2010