Probiotics are living microorganisms promoted with claims that they provide health benefits when consumed, usually by enhancing or restoring the intestinal flora.  Probiotics are generally considered safe to consume, but in rare cases they can cause bacteria-host interactions and unwanted side effects.  There is little evidence that probiotics provide health benefits. The original theory, similar to the modern concept, but not to the term, is more commonly attributed to Nobel laureate Elie Metchnikoff, who postulated that Bulgarian peasants consume yogurt live longer.

The probiotics for a growing market have led to the need for more stringent requirements for confounding the putative benefits of scientific justification with allegedly probiotic microorganisms.  Although many claimed benefits are marketed for use as consumer probiotic products, such as demanding gastrointestinal discomfort, improved immune health,  relieving constipation, prevention of colds, these claims are not supported by scientific evidence.  and are banned as misleading advertising in the United States by the Federal Trade Commission. Since 2019, there have been numerous requests for approval