The Gastrointestinal tract has historically been considered only to be the organ responsible for digestion, absorption and excretion of foods/nutrients. But it becomes more and more clear that is has importance in many other aspects of health and well-being so it for example plays a role in several aspects of immunity.

Micro organisms have a major role in gut function and health, the lower part of the gut is usually habited by several millions of beneficial bacteria. They help breaking down nutrients such as fibres, enable absorption and production of some vitamins and moreover they also prevent the spread of ‘bad’ bacteria which may cause diseases such as diarrhoea or even forms of cancer.

The concentration of more than 400 different species habituating the human gut depends on genetic and environmental factors, and one of these environmental factors is diet. Diet has been shown to influence the growth, maintenance and the occurrence of specific types of bacteria and moreover food can also introduce bacteria into your gut (Fedorak et al., 2005).

Probiotics are foods which contain so called beneficial bacteria. They usually are made up of one species and these must be able to survive in food during storage long enough and still contain large enough amounts to be able to pass the acidic stomach, the duodenum and the small intestine. By now there are many different species of bacteria which are used for probiotics most of them however belong to the lactobacillus or the bifidobacteria family.

Probiotics have been shown to enhance immune function (MacFie and McNaught, 2001); they also seem to have beneficial effects on patients with Inflammatory Bowel Disease (Amandi et al., 2002, Jian et al, 2002). More recently they have been proposed to have some positive effects on hypersensitivity/allergies in children (Jian et al., 2002) however the trials are still ongoing and might be influenced by the amount and type of probiotic given and may vary for different types of allergies. They are furthermore suggested to help to prevent and recover after infections of infants with diarrhoea and potentially be helpful in adult infectious diarrhoea. Similarly diarrhoea occurring during antibiotic use might be improved significantly (Fedorak et al., 2005).

Prebiotics on the other hand can be understood as the food for specific beneficial bacteria. Usually prebiotics are indigestible carbohydrates. Prebiotics may enhance the efficacy and amount of certain bacteria species. Some dietary fibres might work as prebiotics but most fibres are source of energy for many different bacteria species, whereas prebiotics may be fermented only by a small group of bacteria species and as such are source of energy for them in the gut (Derrien et al., 2005). Some prebiotics are even produced by the human intestine itself. Prebiotics in human diet are generally considered to be safe; however with large consumption side effects such as flatulence, bloating and diarrhoea have been reported.

Prebiotics are thought to be beneficial for gut health and as such for overall health and well being as they influence the composition of gut micro flora by favouring the multiplication of specific microbes and preventing the colonisation of others (Derrien et al., 2005). So it is believed prebiotics may have similar positive effects on health as probiotics. However so far the evidence for this idea is low because there were just a few well controlled trials and the metabolic effects of many prebiotics are still being elucidated.

Hence it appears consuming probiotics and prebiotics seems to provide health enhancing effects. So far just some negative side effects of prebiotics have been reported if large amounts have been consumed and these disappeared with reduction of prebiotic intake. As such, both may be a good addition in a well balanced diet and may be moreover of particular use for people suffering of digestive diseases such as IBS and diarrhoea, for children and potentially adults with severe allergies and finally might be useful during antibiotic therapies to maintain good gut micro flora.

Amadini,C., Campieri, M., Gionchetti, F., Morselli, C., Palmonari, V., Rizzello,F., Romagnoli, R. and A. Venturi (2002) Probiotics – Role in inflammatory bowel disease, Digestive Liver Disease, 34l, SUPPl.21, 58-62

Derrien, M. De Vos, W., Ouwehand, A.C., Rautonen, N. and K. Tiihonen (2005) Prebiotics and other microbial substrates for gut functionality, Current Opinion in Biotechnology, 16, 212–217

Fedorak, R.N., Madsen, K.L. and R. Penner (2005) Probiotics and nutraceuticals: non-medicinal treatments of gastrointestinal diseases, Current Opinion in Pharmacology, 5, 596–603

Jian, R., Marteau, P. and P. Seksik (2002) Probiotics and health: new facts and ideas, Current Opinion in Biotechnology, 13, 486–489

MacFie, J. and McNaught, C. E. (2001) Probiotics in clinical practice: a critical review of the evidence, Nutrition Research ,21, 343–353

Andrea Zick Esteem Fitness Nutritionist london