Strain, dose, duration, validated clinical trial studies and scientific substantiation of health claims are needed in order to define a successful probiotic. In particular, the potency of probiotic differs from strain to strain. In this view, we aimed to know whether the single strain or multi-strain construct is more beneficial. We found that the studies were still under debate and mechanisms remain sometimes unclear. No conclusion can be made based on the strain experimentation. Safety data and significant statistical results for efficacy via well-controlled clinical trials are needed.