Probiotics, Prebiotics and the friendly kind of bacteria

Though we’ve all heard about ‘friendly bacteria’ (mostly from the yoghurt adverts..), do we really know what it all means?

Dr Geoff aims to give you some background, or at least tell you what the yoghurt adverts don’t:

The healthy human gut contains many millions of bacteria. Variations in the number and types of these bacteria can influence our health; most obviously when harmful bacteria from contaminated food or water cause food poisoning, dysentery, typhoid or cholera.

In breastfed babies, almost all of the bacteria in their bowels are so-called lactic acid bacteria which ferment carbohydrates to lactic acid; this group includes bacteria of the now well known “bifidus” group. Various types of lactic acid bacteria are used to produce fermented foods like yoghurt, cheese, sauerkraut and salami. The acids and other substances produced by this bacterial fermentation give these foods distinctive flavours and make it difficult for other bacteria to grow in the food which would spoil it or cause illness in those eating it. This has been a traditional way of safely storing highly perishable foods like milk. Breastfed babies are know to have less gut infections than bottle fed babies even where hygiene is good; the domination of lactic acid bacteria in their bowels and the acid conditions these produce in their bowels are one reason for this.


These are live cultures of “friendly” bacteria usually taken in the form of drinks or yoghurt that are intended to change the balance of bacteria within the gut. Most of these “friendly” bacteria are lactic acid bacteria. The theory is that these live bacteria will survive passage through the acid conditions in the stomach and reach the bowel where they will multiply and replace many of the other bacteria including harmful bacteria. The acid conditions caused by the lactic acid they produce will make it difficult for other non lactic acid bacteria to grow in the bowel. The bacteria in most ordinary commercial yoghurt has been killed by heating before it is sold and even those in “live” yoghurt are killed in the stomach and so these are not classed as probiotic.


These are particular types of carbohydrate that are not digested by the human gut and which therefore reach the bowel intact. In the bowel they are fermented by lactic acid bacteria and they greatly increase the proportion of these bacteria in the bowel. Breast milk contains natural prebiotics which have been referred to as the “bifidus factor” because they stimulate the growth of bifidus bacteria in the baby’s bowel.


Check back soon for Dr Geoff’s opinion about their uses, and the truth about the hype!


One thought on “Probiotics, Prebiotics and the friendly kind of bacteria

  1. Pingback: Probiotics: a Fibro friend | Painfully Aware

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