• Lactobacilli and bifidobacteria are the most common types of microbes used as probiotics.
  • Prebiotics increase the number of probiotic bacteria and their activity in the colon, and are an energy source for beneficial bacteria like bifidobacteriaand lactobacilli.
  • Synbiotics combine a probiotic and a prebiotic.


Probiotics is not a new concept. Their discovery is due in part to the work of Russian scientist Élie Metchnikoff at the beginning of the 20th century, although the term ‘probiotics’ did not originate until 1953, when it was coined by Werner Kollath.

Metchnikoff had observed the longevity of certain Eastern European populations who consumed a diet rich in milk fermented by nonpathogenic lactic acid bacteria, recognized for their potential beneficial effects, and while working at the Pasteur Institute, conducted extensive research in this area.22 Countless experiments describing the use of selected microorganisms that belong primarily to the lactic acid bacteria family have been conducted, exploring the prevention or treatment of a variety of conditions.

Probiotics timeline

Initially described as ‘a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance’,23 probiotics are now defined as ‘live microorganisms that, when administered in adequate amounts, confer a health benefit on the host’.24 This definition from the World Health Organization (WHO) has been adopted by Health Canada.

Alone or in combination as tablets, drops, liquids and oral or vaginal capsules, or in fermented foods like yogourt, the most commonly used probiotics in Canada are live bacteria like Lactobacillus and Bifidobacterium species.25 A few common probiotics like Saccharomyces boulardii are yeasts rather than bacteria.


Prebiotics differ from probiotics; they are defined as ‘selectively fermented ingredients that allow specific changes both in the composition and/or activity in the gastrointestinal microflora, thus conferring benefits upon host well-being and health’.26 Prebiotics increase the number of bacteria and their activity in the colon, and are an energy source for beneficial bacteria like bifidobacteria and lactobacilli.27 Their role, essentially, is to promote the growth of beneficial bacteria over the growth of harmful microorganisms.


Synbiotics are defined by the WHO as ‘mixtures of probiotics and prebiotics that beneficially affect the host by improving the survival and implantation of live microbial dietary supplements in the gastrointestinal tract of the host.’28 Synbiotics describe a mixture of prebiotics and probiotics in a single product.