Although evidence indicates that extra doses of "good" bacteria, such as lactobacilli and bifidobacteria, can relieve inflammation and restore harmony, delivering them alive to the colon is not easy. The bacteria can be grown in yoghurt cultures or freeze-dried in capsules, but there is no guarantee that the products in health shops and supermarkets contain the optimum number of bacteria, nor that they will survive the hazardous passage through churning stomach acids and digestive enzymes to the gut. And as Professor Glenn Gibson, a microbiologist at the school of food biosciences at Reading University, explains: "Unlike probiotic bacteria, prebiotic
carbohydrates are not destroyed when cooked."
Professor Gibson and a Belgian colleague, Dr Marcel Roberfroid, of Louvain University, Brussels, coined the term "prebiotics" in 1995.
Prebiotic carbohydrates, known as oligosaccharides, are found naturally in certain fruit and vegetables, including bananas, asparagus, garlic, wheat, tomatoes, Jerusalem artichoke, onions and chicory. They are not digested but go straight to the gut where they are seized on by good bacteria, stimulating the bacteria's growth.
"Because you have more chances of getting prebiotics to the large intestine, you see a bigger response than you would possibly expect with a probiotic," says Gibson.
Anne Woodham, "A good gut feeling," The Times of London, June 11, 2003
An alternative approach to the manipulation of the gut microflora is the use of prebiotics. These are food ingredients that selectively target the colon and may beneficially affect the host by stimulating the growth or activity of specific resident bacteria. Again, the goal is to realise potential health benefits. Dr Glenn Gibson of the UK's Medical Research Council, Dunn Clinical Nutrition Centre, discussed the functional use of prebiotics, referring to the non-digestible oligosaccharides and their influence on bifidobacteria. A number of health-promoting properties are associated with bifidobacteria including an anti-bacterial effect, production of vitamins (particularly of the B Group) and the production of certain immunomodulators that may promote immunological attack against malignant cells.
Liz Tuley, "Functional foods: the technical issues," Food Manufacture, April 1995