Probiotics

Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. That sentence is the International Scientific Association for Probiotics and Prebiotics definition as quoted by the NIH Office of Dietary Supplements. The unit of identity is the strain, not the genus on the front of the bottle.

What are probiotics?

ODS says probiotics are mainly bacteria, with some yeasts, and that they appear in some fermented foods, are added to some foods, and are sold as supplements. Not every food or capsule labeled “probiotic” has a demonstrated benefit.

ODS distinguishes related terms. Prebiotics are typically complex carbohydrates that gut microbes use as fuel. Synbiotics combine prebiotics and probiotic organisms. Postbiotics are preparations of dead or fragmented microorganisms, with or without metabolites.

NCCIH gives a shorter public wording: live microorganisms intended to have health benefits when consumed or applied.

Why does the strain matter more than the species?

ODS says a complete name includes genus, species, subspecies if used, and an alphanumeric strain designation. Effects can be nonspecific, species-specific, or strain-specific. Recommendations, it says, need to be strain-specific.

A label that names only Lactobacillus or Bifidobacterium has not named the organism that was studied.

What does CFU mean on a probiotic label?

CFU means colony-forming units, a count of viable cells. ODS says many supplements list 1 to 10 billion CFU per dose, and some list 50 billion or more, and that a higher CFU count is not necessarily more effective.

U.S. labeling rules, ODS notes, require the total weight of microorganisms, which can include dead cells. Manufacturers may also list CFU. Because organisms can die on the shelf, ODS says users should look for CFU at the end of shelf life, not at manufacture.

Are prebiotics the same as probiotics?

No. NCCIH states that directly. Prebiotics are nondigestible food components that selectively stimulate desirable microorganisms. Synbiotics combine the two.

What safety notes do the federal pages publish?

NCCIH reports cases of severe or fatal infections in premature infants given probiotics, and that FDA has warned health care providers about that risk. ODS records the 2023 FDA news release on probiotics in preterm infants, including reports of infant death and other adverse events, and the fact that probiotics have not gone through FDA’s premarket process for medical uses.

This page does not name retail brands. Strain designations belong on labels and in papers. Storefront pages for Seed, Align, or Culturelle are not sources here.