As component parts of the intestinal flora (the microbes of the digestive tract) they suppress the growth of pathogens, regulate digestion and strengthen the body’s defences by stimulating the immune system.
Products containing concentrations of probiotic bacteria could, if taken daily and over an extended period of time, relieve diarrhoea and chronic intestinal inflammations. They are also helpful in restoring normal gastro-intestinal function where antibiotics have had an adverse effect.
A prerequisite for achieving these positive effects is that as many of the bacteria as possible survive the journey through the stomach and its aggressive gastric acid. Often the effect is only temporary because the bacteria cannot settle permanently in the gut.
There is also some controversy surrounding the use of probiotic yogurts that contain only small numbers of bacteria, since it is not clear that they have any positive effect on intestinal function.