Are probiotics and other functional foods the medicines of the future?
Susan Holmes, PhD, BSc, SRN, FRSH.
Director of Research and Development and Professor of Nursing, Faculty of Health, Canterbury Christ Church University College, CanterburyPeople have believed for centuries that food is capable of both preventing and treating disease. This is true, at least to some extent, and it is clear that the nutrients food provides play vital roles in preventing and managing disease. In more recent history, there has been a move away from food towards drugs, which have been increasingly used to prevent, alleviate or treat disease. However, the discovery of nutrients, and the development of nutritional science, has led to an increasing recognition of the role of nutrition in maintaining health and, in turn, to the rise of so-called 'healthy eating' during the 1970s and 1980s. Continuing research has provided new evidence and a change in emphasis from the negative or harmful aspects of food towards the idea that food or its components may benefit health; this, in turn, has led to the development of a range of products known as 'functional foods' (Sheehy and Morrissey, 1998).
Although there is no universally accepted definition, functional foods generally refer to those believed to prevent or treat diseases (Goldberg, 1994). Although it can be argued that all food is 'functional', the modern concept is that such foods must provide benefits over and above the nutrients required for normal health. Thus Goldberg defined functional foods as 'any food or food ingredient that has a positive effect on an individual's health, physical performance or state of mind, in addition to its nutritive value'. Such components may include specific minerals, vitamins, fatty acids or dietary fibre and/or biologically active substances such as phytochemicals or other antioxidants and probiotics that contain live beneficial bacterial cultures (EUFIC, 2003).
The many physiological functions of the GIT, such as digestion and absorption, colonic fermentation, and gastrointestinal tract-associated immune activities, among many others (Robertfroid, 2002), make this the focus of much attention primarily due to the large number and variety of bacteria that live symbiotically with the host. Indeed, human adults carry over 1kg of bacteria in their gastrointestinal tract and excrete their own weight in bacteria every year (EUFIC, 2003). Robertfroid (2002) points out that such bacteria play a number of important physiological and/or metabolic roles (Box 1).
Although there are many definitions of probiotics, they can be simply described as 'non-pathogenic micro-organisms that, when ingested, exert a positive influence in the health or physiology of the host' (Marteau et al, 2002).
Since the value of probiotics remains to be proven, attention is increasingly turning to the use of prebiotics as a more certain way of securing potential benefits without associated difficulties (Rastall and Maitin, 2002). These, too, are treated as functional food ingredients and comprise complex oligosaccharides, such as dietary fibre, that are not digested by humans but are broken down in the gut by microbial action, thereby providing nutrients to promote the growth and colonisation of probiotic bacteria.
Probiotics are believed to hold promise for the future as they clearly allow modulation of the endogenous intestinal microflora and the immune system (Marteau et al, 2002).
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