As the health benefits of ingesting live bacteria become more evident, foods are now being produced that contain probiotic bacteria. The data to support label health claims for probiotic products are often difficult to provide. The experimental evidence to identify probiotic microorganisms and to demonstrate their efficacy in clinical trials is more challenging than for other potential functional foods because effects are mediated by living microorganisms and may therefore be influenced by the status of these microorganisms. Clinical trials to show efficacy are expensive. Obtaining appropriate samples is difficult. A scientific consensus is building to support the claim that the ingestion of certain probiotic bacteria reduces lactose intolerance and can reduce the duration of rotavirus diarrheas. Some probiotic bacteria have "generally accepted as safe" status; proof of the safety of any probiotic is essential. Japanese health regulatory officials, using their Foods for Specific Health Use system, have approved human health claims for over 20 probiotic products. On the other hand, at this time, no probiotic product is sold in Canada that carries a label health claim. This illustrates the considerable discrepancies across countries in perception of health effects of probiotics.