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Probiotics - What are they? 8th part 1 in a series

Probiotics - What are they? 8th part 1 in a series


By Don Pearson, Technical Director BioBrew Ltd

The internationally accepted definition of a probiotics is that they are "livemicroorganisms which when administered in adequate amounts confer a health benefit on the host." (WHO/FAO, 2002)

Firstly, probiotics must be alive when administered. Secondly, they must survive, intact, to reach the lower intestine where they do most of their work. We will revisit this once we look at the suit of organisms that are contenders for the role of a probiotic.

The list of possible contenders for probiotic organisms that are naturally found in the gut is surprising small given the vast number of bacterial species in the gut. The most serious contenders are in the Firmicutes (Lactobacillus and Streptococcus) and the Actinobacteria (Bifidobacterium). These bacteria are routinely used because they are relatively easy to culture and are often used for food fermentations (Tannock, 2004).

According to Sanders (2008), “The term “probiotic” is sometimes erroneously used as a synonym for putatively beneficial members of commensal microbiota. The context for this misuse is the assertion that certain dietary or environmental factors may “encourage your native probiotics.” Members of human commensal microbiota are often sources from which probiotics are isolated, but, until such strains are isolated and then adequately characterized for content, stability, and health effects, they are not probiotics.”

Commercially probiotics come in two forms. These are freeze-dried or as an intact fermentation.

The freeze-dried formulations require special handling and microbe numbers on the label are at the time of manufacturing, not at the time of use. Freeze drying is an excellent way to store microbes and food fermentation bacteria and yeast are often stored this way.  They require careful handling and special conditions to maintain viability during the rehydration process. Unfortunately, this is how most probiotic organisms are presented commercially and it is difficult to tell whether the consumer is getting a probiotic dose as per the label.

With intact fermentations, the bacteria are alive and active.  Again, manufacturers often quote numbers bacteria at the time of manufacture, so look for a product with viability numbers at the end of shelf life, i.e., a guarantee of the numbers of live microbes throughout the entire shelf life. The few studies historically that compared freeze-dried bacteria to intact fermentations show that intact fermentations are around 100 times as effective as freeze-dried bacteria on a cfu (colony forming unit) enumerated basis (Saxelin, 1996).


Probiotic micro-organisms need to be fresh, viable, and in adequate numbers at the time of taking. Freeze-dried products are less efficacious than fresh products.

Sanders M. E. (2008) “Probiotics: Definition, Sources, Selection, and Uses” Clin Infect Dis.- S58-61

Saxelin, M. (1996) “Colonization of the Human Gastrointestinal Track by Probiotic Bacteria” Nutrition Today Supplement, Vol. 31 pp 5S-8S

Tannock, G. W. (2004) “A Special Fondness for Lactobacilli” Appl. Environ. Microbiol., 70(6):3189. DOI: 10.1128/AEM.70.6.3189-3194.2004.

WHO/FAO, 2002. Report of a Joint FAO/WHO Working Group on Drafting Guidelines for the Evaluation of Probiotics in Food, London, Ontario, Canada, 30 April–1 May 2002 [FAO Food and Nutrition paper 85], pp. 1–50, Rome, Italy: World Health Organization (WHO), Food and Agriculture Organization (FAO)