I want to grow my own probiotic yoghurt... you know walk into a health food store, pull one of those expensive probiotics from their fridge and stick it into a yoghurt starter. There are two advantages: cost and quantity. However I am not sure of the efficacy of doing this. Do the strains of the probiotic reproduce in the starter proportionately. How often can I create a new batch before I need to start again? Is anyone doing this successfully? How could I tell if the integrity of the yoghurt is still good? Today I have grown my first batch of yohurt from a probiotic powder, without even a proper starter, so the process works in some respects. Tastes fine. It's just that I do not know what I am getting. Frankly after reading some of the literature floating around on the web, I am not sure we can really be sure of what we are getting in the bottle of probiotic in the fridge of the health food store. Of course I can go down the suck it and see route, but it seems that there is uncertainty piled on top of uncertainty, particularly if you are taking other meds. The other point is that if competing strains in my yoghurt are killing each other in a relatively sterile environment, what must be happening in the gut, where the billions of bugs must devastate any probiotic we ingest. Are there any studies that show measurable changes to gut environments or faecal composition from the use of probiotics, other than those that rely on patient observation?