of the University of Florida School of Medicine
and his colleagues reviewed several studies that compared health impacts using live microbes versus those that had first been killed by heat or ultraviolet radiation. The dead bugs were just as effective as live ones, they report, but “considerably safer for the host.” For instance, they appeared less likely to provoke an overzealous immune response.
One study worked with Lactobacillus rhamnosus GG
, better known as LGG. Researchers administered high doses of the bacterial strain to human cells that normally line the interior surface of the gut. When stimulated in a way that simulated the presence of a pathogen, the gut cells revved up a bigger inflammatory response than when the probiotics were absent. Both live and dead LGG induced fairly comparable responses — ones that would be expected to improve the gut’s ability to fight infection.
Then the researchers repeated the experiment, this time with gut cells that appeared healthy — i.e. not under siege by pathogens. Here, live LGG triggered significant inflammation. Which is not a beneficial response, since healthy cells might be slammed by deadly chemical shrapnel unleashed by immune cells. A similarly big dose of dead LGG caused only mild inflammation.