Food Feeding the Fifty Billion

Two types of functional food are not designed to provide us with dietary components, but to provide food for the microbes that inhabit our gut. These are the so-called probiotic and prebiotic foods. The former are meant to introduce better bacteria into our intestines, while the latter feed the bacteria that are already there in the hope of boosting more of the good bacteria and thereby helping them crowd out the bad bacteria. Various health claims have been made for these foods. 

With regular consumption of probiotics the composition of the gut microbes can be changed although they have to be consumed regularly if this change is to persist. The new bacteria might also make the 

These carbohydrates may be added to all kinds of foods, such as cereals, cakes, biscuits, and health drinks. They can be extracted from things like chicory root or produced from sugar by the action of specific enzymes. A little FOS is also to be found in bananas, leeks, and wheat, and the other prebiotics also occur naturally, but no fruit or vegetable by itself can supply the 5 g of oligosaccharides needed daily to boost the good bacteria. Indeed the normal person s diet contains only about 2 g of these carbohydrates. 

Mother s milk also contains several prebiotic carbohydrates that the baby cannot digest and these too feed the friendly bifidobacteria in the baby s gut. The more bifidobacteria there are in the gut the less there will be of those which cause gastrointestinal infections, namely the various species of Campylobacter, Salmonella and Clostridium. In formula fed babies these bad bacteria account for much of the microflo- 

Infant formula feeds now contain the oligosaccharides GOS and FOS with more of the former than the latter, the ratio being around 90% to 10%. Feeding a baby the new kind of formula feed leads to levels of acid that are more in accord with what is found with babies fed on breast milk and this reflects the improved composition of bacteria in the baby s intestines. 

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