SUPERFOODS are as well known now as Superman was in the Seventies, and are credited by some with almost as much power as the legendary superhero himself.

While they won't give you powers of flight or the strength to chuck buses, nutrient-dense superfoods - such as pomegranate, coconut oil, kale and red cabbage - are so-called as they're believed to be ultra good for us, helping boost general health, super-charging the immune system, guarding our memories and keeping illness at bay, including cancers and heart disease.

While kale and cabbages have obviously been around for donkey's years, the term 'superfood' hasn't, but when something is granted the impressive label, sales often soar. The amount of red cabbage bought in Britain last year grew by nearly 50% compared to the previous 12 months, spending on kale has doubled in the last five years, and sales of coconut oil in the UK has nearly tripled in just two years.

But are these so-called superfoods the dietary magic bullets they're made out to be?

No, says British Dietetic Association spokesperson, Kelly McCabe.

While agreeing that certain foods have indeed been reported to have cancer-protective effects and other health benefits, she stresses: "There's no such thing as a 'superfood'.

"No one food in isolation can have a profound effect on our health, or provide all the nutrients we need. Instead, we should strive for a 'super-diet', which includes a wide range of these so-called superfoods."

Exotic-sounding and often pricey superfoods - such as goji berries, chia seeds and teff grains - may frequently be in the headlines, and linked with health-conscious celebrities like Madonna and Gwyneth Paltrow, but the truth is that many of the healthiest foods around can be found in the fridges and cupboards of ordinary folk.

"We forget all the humble things in our cupboards," says McCabe, a cancer specialist dietician.

"If I had to choose one food, I'd definitely choose an egg. It's our most easily digestible form of protein, and it contains every vitamin and mineral that we require, with the exception of vitamin C.

"It's a nutritionally complete food - and a normal food we'd eat as part of our everyday diet, as opposed to goji berries, wheatgrass and chia seeds."

The other top ordinary superfoods are brightly-coloured fruit and vegetables, like tomatoes, carrots, beetroot and sweet potato.

Fruits, veg, pulses, beans and plants produce a wide variety of compounds called phytochemicals, packed with potential benefits for human health. They include groups of substances such as polyphenols and carotenoids and sometimes produce antioxidant effects, helping mop up free radicals in the body that may trigger disease.

"Think of the colours of your foods," says McCabe. "Phytochemicals are usually the pigments in the food, so the idea of eating the rainbow is based on science."

Lycopene, the red pigment in tomatoes and watermelon, is thought to have anti-inflammatory effects, while orange-coloured vegetables, like sweet potato, butternut squash, and red or orange peppers, contain beta-carotene, an antioxidant and type of vitamin A.

Purples and reds, like blueberries, blackberries and red cabbage, will normally contain anthocyanins, powerful antioxidants. Red cabbage also contains sulforaphane, thought to have anti-cancer and anti-inflammatory properties.

"Sulforaphanes have protective, anti-inflammatory effects on health, and that's where all the hype about red cabbage comes from," explains McCabe. "But you'll get similar compounds from other green leafy vegetables and purple fruits or veg in the diet - you don't need to eat a whole red cabbage a day.

"Eating a large variety of different colours, even if they're everyday British foods, is what should be aimed for."

A good, varied diet is thought to be important because nutrients have a synergistic effect - they perform best in combination - so different nutrients or phytochemicals will interact with one another to produce beneficial health effects.

"There's no scientific data to support the idea that one food in isolation can have a significant impact on our health," explains McCabe.

"It's the diet we eat over a long period that subtly influences our health - not eating a punnet of blueberries every day for a week."

And for those who aren't too keen on fruit and veg, many herbs and spices, such as garlic and turmeric, are also packed with health-boosting phytochemicals.

"People will always want to hear that you should go out and buy this really unusual food that's just been discovered, because the message about everything in moderation is really boring," McCabe points out.

"But all the science suggests that's what's necessary. People want a magic bullet food, a really quick fix, but I don't believe there will ever be one food that has that desired effect on our health.

"It's much better to invest your money in eating a wide range of good quality traditional food, rather than spending a fortune on something like goji berries, manuka honey and chia seeds, because you can get all the nutrients you get from those in other foods, in a good balanced diet."

She won't call them 'superfoods', but here are some of the ingredients McCabe says are of "particular interest" when it comes to boosting health and protecting against cancer...

Turmeric: The active ingredient in this spice is curcumin, a powerful antioxidant believed to have anti-inflammatory properties.

Chilli Pepper: Chilli or cayenne peppers contain capsaicin, a plant chemical found to reduce pain when applied topically, plus vitamin A and antioxidant carotenoids.

Ginger: It's been used as an anti-sickness remedy for centuries as it contains volatile oils like gingerol, believed to stimulate saliva and gastric function.

Red Grapes: Their skins contain resveratrol, a compound shown to reduce inflammation and have antioxidant properties.

Avocado: Rich in heart-healthy monounsaturated fatty acids, such as oleic acid, and the antioxidant vitamins C and E.

Tomatoes: Contain lycopene, an antioxidant chemical found to protect against prostate cancer.

Cruciferous Vegetables: These leafy greens, including broccoli, kale, kohlrabi, cabbage, cauliflower and rocket, are packed with sulforaphanes which are linked to a lower cancer risk, particularly for prostate cancer.

Allium Vegetables: Onions and garlic contain sulphur compounds which help lower blood pressure. Garlic also contains allicin, which promotes antioxidant activity and has powerful antibacterial and antiviral functions. Onions have high concentrations of quercetin, which has anti-inflammatory benefits.

Brightly Coloured Berries: Blueberries, raspberries and strawberries are a rich source of anthocyanins and have been found to have antiviral, antibacterial, antioxidant and anti-inflammatory properties.

Beetroot: Rich in nitrates, beetroot has been linked with improved blood flow and lower blood pressure. It's also full of antioxidants, potassium, magnesium, vitamin A, B6 and C.

Pomegranate: Juice from the seed pulp is rich in tannins, flavonols and anthocyanins, all powerful antioxidants. Pomegranate juice has been found to benefit patients with prostate cancer, and it may also help reduce oestrogen production, potentially useful for those with oestrogen-dependent breast cancer.

Carrots, Peppers and Sweet Potato: Beta-carotene, an antioxidant vitamin present in orange veg, and other carotenoid pigments have been shown to enhance immune function.

Oily fish: Contains omega-3 fatty acids found to help improve natural inflammatory responses and possibly support heart and brain health.

Eggs: A naturally-rich source of iron, vitamin D and a rich mixture of amino acids, the building blocks of proteins.

Brazil nuts: One of very few dietary sources of selenium, a mineral integral to immune function.

Dark Chocolate (cacao): The cacao (or cocoa) bean is full of protective flavonols which have antioxidant qualities and have been shown to improve vascular health.

Soy: A higher intake of soy products, which contain isoflavones, is linked with reduced risk of certain cancers and lower cholesterol levels.