Functional Foods

The concept of functional foods has arisen from our deepening understanding of the biochemistry of nutrition and the realization that many of the 'diseases of civilisation' - diabetes, heart disease, and cancer, for instance - are diet related. As the populations of developed countries age, these diseases are putting an increasing strain on health resources. Long-term changes to our diet could thus produce an immense benefit. There is much evidence that even among younger people modern sedentary lifestyles have created a situation in which dietary intake of some essential factors is inadequate. Fashionable low carbohydrate diets, for instance, restrict calcium intake and contribute to bone problems in later life.

A food can be described as functional if it can be demonstrated to affect beneficially one or more target functions in the body, beyond adequate nutritional effects, in a way that is relevant to either an improved state of health and well-being and/or reduction of disease.

Vitamins and minerals are functional foods that have been used for many years; they are well understood and have clear recommendations from most governments for minimum dietary requirements. But it has been realised that minimum requirements may not be enough. Minimum means sufficient to prevent deficiency diseases but vitamins have been shown to have additional beneficial actions. Vitamin C for instance was initially recognised as the factor that prevents scurvy but it has a wider role in protecting the body from harmful oxidising free radicals that initiate degenerative changes and cause mutations in DNA.

Several other substances have similar protective properties. Vitamin E is perhaps the strongest of these but many other chemicals found in foods as diverse as tea, tomatoes and onions are also active against free radicals. These compounds - many of them, in chemical terms, flavonoids - often give flavour and colour to foods but they are also increasingly recognized as conferring long-term health benefits. Lycopene gives the red colour to tomatoes but it is also a powerful quencher of dangerous free radicals that can attack vital cell processes.

As a practical example, cataract afflicts a significant proportion of the older population: in the UK the annual waiting list for cataract operations is 700,000, but vitamins C and E could reduce the incidence quite dramatically.

Research has shown that one way of obtaining the benefits of these functional ingredients is to eat a more varied diet every day. The Japanese have a much lower incidence of the diseases of civilisation than Westerners despite being one of the world's richest countries. Research has shown that they eat an average of 27 different foods a day whereas the recommended minimum in the West is 30 different foods per week.

Many classes of functional foods have now been identified. Probiotics and prebiotics affect the bacterial flora that lives in the gut. Probiotics are live cultures, such as yogurt, that can survive the stomach acids and change the composition of the gut flora. Prebiotics are non-digestible food ingredients that stimulate the growth of beneficial bacteria in the gut.

Omega 3 fatty acids, found in oily fish such as mackerel, tuna and anchovies, are functional foods. They are discussed under Diet and Behaviour. A great deal of work is currently underway on substances such as lycopene (to prevent bowel cancer and other chronic illnesses), lutein, from green leafy vegetables (for eye health), and green tea extract (antioxidant).

Functional foods are concerned with the prevention of disease or the reduction of disease risk. They are not to be seen as cures: products used in a curative sense are sold as medicines with a defined set of indications under the supervision of a qualified physician.