Today's New York Times reported on a Lancet study where probiotics proved fatal when used for pancreatitis. However, the story failed to bring up the question: which probiotics were used?

Not all probiotics are necessarily helpful--investigations into the ideal mix of gut bacteria is still in its infancy.

> Which of the 400 species* of microbes in the adult human intestine are "good"? Most probiotic studies look at different strains therefore studies are hard to compare.

> For probiotics, what if you deliver the "good bacteria" to the wrong place? The small intestine is prone to bacterial overgrowth--even if it's "good" bacteria. (The large intestine has approximately 10¹¹ organisms per gram of content (colon) but the small intestine contains only 10^0-2 organisms per gram of content*)

> In severe pancreatis, studies have shown small intestine bacterial overgrowth (SIBO) to positively correlate with the severity of the pancreatitis*.

> Could the Lancet study's commercial probiotic, **Ecologic 641, have exacerbated SIBO in the pancreatitis patients?

Given that the probiotic mix contained two strains of bifidus and that bifidus may overgrow in the small intestine, this is entirely possible.

Notes:
* source: Alterations in intestinal microbial flora and human disease, Current Opinion in Gastroenterology, Volume 24(1), January 2008, p 11-16

** Ecologic 641 contains Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus salivarius, Lactococcus lactis, Bifidobacterium bifidum, and Bifidobacterium lactis.