Superfoods give modern health consumers everything we need – a hit of essential nutrients in an edible form (even if it’s not always to your taste). There’s also that hint of the exotic which appeals to a market willing to experiment with peculiar foodstuffs.

Clearly our appetite for superfoods is insatiable. To the layperson it seems that they are popping up faster than birds infected with H5N1. Barely have you managed to track down a good source of the latest superfood when it seems it has been superseded by another. Pomegranates are already yesterday’s news: the latest superfood is the wolfberry. This deep-red, dried fruit is grown in China; about the size of a raisin and tasting like a cross between a cranberry and a cherry, it is a small powderkeg of goodness, containing 500 times the amount of vitamin C by weight than oranges, with more antioxidants than pomegranates. And it is the richest source of beta-carotene of all known foods.

Recent research by Dr Harold Corke at the University of Hong Kong found that wolfberries, also called goji berries, significantly reduced blood glucose levels, bad cholesterol and triglycerides (fatty acids in the blood stream that lead to heart disease, diabetes and weight gain). Meanwhile the journal International Immunopharmacology has reported that wolfberries had a significant effect on the size of cancer tumours in mice. Further research in China has found the fruit to be effective in preventing the growth of leukaemia cells. Chinese studies also suggest that wolfberries have anti-ageing properties.

But perhaps if the wolfberry doesn’t appeal you could opt for maca. This addition to the superfood genre is a root vegetable, similar to a sweet potato but sold in the West as a powder. It’s been dubbed “natural Viagra”, with double-blind trials suggesting that it improves sexual desire, sperm count and sperm motility. It may offer other benefits: Dr Hugo Malaspina, a cardiologist based in Lima, says that the regulating effects of maca on the pancreas and pituitary and adrenal glands have helped over 200 menopausal patients.

Then there’s hemp oil, one of the richest sources of the essential fats that play a key role in brain function, reproduction and food metabolism, and in ailments such as heart disease, Alzheimer’s, cancer and arthritis. The oil is also a good source of GLA, which is believed to help in the treatment of pre-menstrual tension. A recent study published in the Journal of Dermatological Treatment compared dietary hemp oil with topical treatments for dermatitis: significant improvements were noted in the group taking the oil.

The problem with the superfood Zeitgeist is that the foods themselves are often expensive and hard to come by. (The humble broccoli stalk no longer quite cuts it in the new superfood cabal: the more far-flung the source, the more we love it.) But, more strikingly, there is no single authoritative definition of what makes a food “super”.

“Ecological footprint” and “carbon credit”, for instance, can be found in the Collins English Dictionary, but “superfood”, arguably a more common part of our vernacular, is not. Meanwhile, ask your GP which superfoods will work best to combat heart disease, allieviate osteoarthritis, normalise the pH of your stomach and prevent cancer (claims all being made for the pomegranate) and you’ll probably be answered with a raised eyebrow.

Michael Van Straten, a naturopath, whose new book Superfoods Superfast is published next month, believes that foods become “super” if they are nutrient-dense and capable of combating serious disease and restoring the body. He lists over 200 fruits and vegetables that have already been called superfoods or are waiting in line for the necessary publicity — such as the strawberry which, it appears, is going to be 2006’s blueberry.

According to Jane Clarke, The Times nutritionist, “a true superfood provides the most concentrated, usable form of nourishment to cells which govern our immune systems, our hormones, our weight and our ageing processes”. But she stresses that: “It is important not to rely on a single superfood and expect it to achieve wonders. Many can only be eaten or taken in small quantities. They can provide extra help, but the most important tactic is to maintain a varied and healthy diet.”

The British Nutrition Foundation agrees. While acknowledging the benefits of less common superfoods such as bee pollen and sea vegetables, Joanne Lunn, a BNF nutritionist, says that the key message is that a broad variety of less expensive fruits and vegetables is the key to keeping us all healthy.

“We welcome any excitement over healthy foods like beetroot or watercress, that encourage people to go out and buy them,” says Lunn. “But our concern is that the flurry which results in the elevation of individual foods eclipses the more important message that we should eat a wide range of fruits, vegetables, proteins, good fats and complex carbohydrates.”

What identifies a superfood comes down to who you ask. A nutritionist is more likely to opt for a food that is the most nutrient-packed and most easily digested; a doctor might list those fruits and vegetables that have been subjected to the most robust scientific research – the most recent being broccoli, which is rich in isothiocyanate and sulphoraphane, substances which are believed to help the body to fight cancer.

Any fruit and vegetable will help your health – and the more the better, according to a recent study in the medical journal The Lancet, which reports that there is strong evidence that we should eat more than five servings a day of these foods if we want to maximise our protection against heart disease and stroke.