Sales of blueberries, walnuts and spinach and other more esoteric things like goji berries, spirulina and chlorella have taken off in the past few years as, everywhere you look, something seems to be telling you about their particular 'health' benefits. Eat them, we're told, to help reduce the risk of cancer and heart disease. But where’s the science?
Actually, there is no definition of superfood. It gets applied to foods from oats to walnuts, spinach to yoghurt, turkey to watercress and beetroot. Meat and fish contain protein and other nutrients. Fruit and vegetables also contain essential vitamins, minerals and other phytochemicals (bioactive non-nutrient components) that are good for health. Labelling some as superfoods could give the impression that they are more health-enhancing than others.
The fruits and vegetables given the superfood tag tend to be high in antioxidants such as vitamin C. The flavonoids, responsible for the colour of dark fruits such as blueberries, and other plant chemicals such as beta-carotene, are also known for their antioxidant properties. This is why brightly coloured fruit and vegetables are considered especially beneficial.
Opinion, based on scientific research, is that because antioxidants are especially effective at combating free radicals - harmful molecules that damage cells and DNA and can contribute to ageing, heart disease and cancer - they make fruit and vegetables particularly good for health.
But phytochemicals, also present in less brightly coloured fruit and vegetables not classed as superfoods, could also act in other ways to protect against disease. Scientists investigating the different ways phytochemicals can act believe too much importance may have been attached to antioxidant activity, and not enough to the other beneficial effects of phytochemicals.
Can all these claims be legal? Following EU legislation introduced in 2007 to prevent unsubstantiated health claims being made for foods, terms such as 'superfood' have to be backed by evidence explaining why the food is healthy and no foods will be allowed to claim they are 'good for your heart', 'help lower cholesterol' or are one of the growing list of 'superfoods', without scientific backing.
During the period before the legislation comes into force, food producers must prove that any claims can be backed up by evidence. Products that are high in calcium, for instance, can legitimately claim that calcium is good for bones. Oats have been shown to help reduce cholesterol as part of a low-fat diet and this claim could be made on a product. So by this time next year, there may be a centralised list of approved claims available for all to use across the European Union.
Eating exotic foods may offer health benefits we don't yet understand. But just because they're eaten in other parts of the world where there is a lower incidence of certain diseases, however, doesn't mean that they'll give the same protection to those following a very different diet and lifestyle in the UK. It may also be that what's important is how a particular food works in combination with other foods.
Most people fail to meet the target of five portions of fruit and vegetables a day. As long as we don't reject some fruit and vegetables in favour of more fashionable ones, publicity that encourages consumers to eat more fruit and vegetables is to be welcomed.