Dead or alive: Benefits of probiotics need live organisms

By Stephen Daniells

- Last updated on GMT

Dead or alive: Benefits of probiotics need live organisms
The potential beneficial effects of select bacterial strains are dependent on the organisms being alive, says a new study that supports the WHO definition of probiotics as being ‘live microorganisms’.

Animal and cell experiments showed that the immune system modifying effects of the strain Lactobacillus salivarius​ ssp. salivarius​ CECT5713 was dependent on the bacteria being alive, according to findings published in the European Journal of Nutrition​.

An area of ongoing debate is whether the dead forms of beneficial bacterial strains have a role to play in conferring benefits to the host in formulations – even if they did not meet the World Health Organization definition of probiotics as being “live microorganisms”​.

According the FAO/WHO, probiotics are defined as "live microorganisms which when administered in adequate amounts confer a health benefit on the host".

“Although some studies have proposed that the viability of probiotics is not essential to exert its anti-inflammatory effect, their effects may be due to their immunostimulatory DNA,”​ wrote researchers from the University of Granada in Spain and the University of London in England.

“However, this is not a constant feature in all probiotics since different in vitro studies have reported that viable probiotic is required to exert anti-inflammatory effect.”

According to their data, live or ‘viable’ L. salivarius​ ssp. Salivarius ​CECT5713 (Biosearch Life, Spain) is “essential for displaying the beneficial effects”​.

Study details

The researchers compared live and dead (heat treated) bacteria in a rat model of colitis and concluded that “the viability of the probiotic was required for its anti-inflammatory activity”​.

This was followed by a test with Caco-2 cells, a line of cells similar to those found in the lining of the intestine. Results from this assay showed that the when the cells were exposed to either interleukin-1B (IL-1B), a compound that plays a role in the inflammatory response, or E. coli resulted in increased levels of interleukin-8, another inflammatory compound. The probiotic, however, significantly inhibited the production of IL-8, said the researchers.

Finally, the probiotic was tested in mice with an altered systemic immune response, and was found to inhibit the production of tumor necrosis factor-alpha (TNF-alpha), a well-established marker of inflammation.

“Most of the studies performed with probiotics have been focused on their beneficial effects on the gastrointestinal tract,”​ wrote the researchers.

“However, it is more and more evident that although these microorganisms may exert their beneficial effects due to the well-known ability to modulate intestinal microbiota and affect the intestine immune response, these effects are not restricted to the gastrointestinal tract.”

Source: European Journal of Nutrition
Published online ahead of print, doi: 10.1007/s00394-011-0221-4
“The immunomodulatory properties of viable Lactobacillus salivarius ssp. salivarius CECT5713 are not restricted to the large intestine”
Authors: B. Arribas, N. Garrido-Mesa, L. Peran, D. Camuesco, M. Comalada, et al.

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