I have another source which claims that 100ml of kefir contains 100 billion CFU (sorry it’s in a different language and can’t quote it), but I don’t think anybody can say for sure. Kefir’s CFU count depends on many factors such as length of fermentation, grain-milk ratio, type of milk used (raw vs. pasteurized) etc. I think my source above was using raw milk kefir (which generally contains more probiotic strains and CFU as milk still has those as well. There is no doubt in my mind that kefir is very beneficial, perhaps more than probiotic pills, but both give you different options. Kefir gives you the number of beneficial bacteria, some of them very harmful to pathogens. Commercial probiotic gives you certainty in the CFU count. This is my interpretation of the need for both.