The World Health Organization defines probiotics as “live microorganisms which when administered in adequate amounts confer a health benefit on the host”
SOURCE: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1479485/ Food and Agriculture Organization and World Health Organization Expert Consultation. Evaluation of health and nutritional properties of powder milk and live lactic acid bacteria. Córdoba, Argentina: Food and Agriculture Organization of the United Nations and World Health Organization; 2001. [cited 2005 September 8].