Safe and efficacious probiotics: what are they?

Each year, >20 billion doses of probiotics are used by healthy people and by those diagnosed with a range of medical conditions. Compared to many pharmaceutical agents, probiotics are well tolerated and extremely safe, and serious adverse effects rarely occur. Nevertheless, as many new researchers enter the field and companies launch "probiotic" products, it is essential that standards are set for naming a product "probiotic" to show that it meets an acceptable level of safety and efficacy, and to understand the strengths and limitations of its activity. In this Opinion article, recommendations are made based upon the current understanding of scientific, clinical and regulatory issues, with a special focus on safety.