Probiotics (live microorganisms for oral consumption) are undoubtedly popular, not least they are being cleverly promoted as a quasi panacea. But are they as safe as their manufacturers try to convince us? A synthesis and critical evaluation of the reports and series of cases on the infectious complications related to the ingestion of probiotics was aimed at finding out.

The authors extensive literature searches located 60 case reports and 7 case series including a total of 93 patients. Fungemia was the most common infectious complications with 35 (37.6%) cases. The genus Saccharomyces was the most frequent with 47 (50.6%) cases, followed by Lactobacillus, Bifidobacterium, Bacillus, Pedioccocus and Escherichia with 26 (27.9%), 12 (12.8%), 5 (5.4%), 2 (2.2%) and 1 (1.1%) case, respectively. Adults over 60 years of age, Clostridium difficile colitis, antibiotic use and Saccharomyces infections were associated with overall mortality. HIV infections, immunosuppressive drugs, solid organ transplantation, deep intravenous lines, enteral or parenteral nutrition were not associated with death.

The authors concluded that the use of probiotics cannot be considered risk-free and should be carefully evaluated for some patient groups.

Other authors have previously warned that individuals under neonatal stages and/or those with some clinical conditions including malignancies, leaky gut, diabetes mellitus, and post-organ transplant convalescence likely fail to reap the benefits of probiotics. Further exacerbating the conditions, some probiotic strains might take advantage of the weak immunity in these vulnerable groups and turn into opportunistic pathogens engendering life-threatening pneumonia, endocarditis, and sepsis. Moreover, the unregulated and rampant use of probiotics potentially carry the risk of plasmid-mediated antibiotic resistance transfer to the gut infectious pathogens. 

And yet another review had concluded that the adverse effects of probiotics were sepsis, fungemia and GI ischemia. Generally, critically ill patients in intensive care units, critically sick infants, postoperative and hospitalized patients and patients with immune-compromised complexity were the most at-risk populations. While the overwhelming existing evidence suggests that probiotics are safe, complete consideration of risk-benefit ratio before prescribing is recommended.

Proponents of probiotics will say that these risks are rare and confined to small groups of particularly vulnerable patients. This may well be so, but in view of the often uncertain benefits of probiotics, the incessant hype and aggressive marketing, I find it nevertheless important to keep these risks in mind.

As with any therapy, the question must be, does this treatment really generate more good than harm?

3 Responses to Probiotics are NOT entirely risk-free

  • Wait a minute. Does this mean I have to worry about commercial saurkraut?

    • You are likely fine with your commercial saurkraut. While standards do change from country to country, most canned saurkraut you buy in a grocery store has been pasteurized/heat treated to kill off bacteria. You still get that nice taste but many of the beneficial effects of the bacteria are lost as they die off during cooking. This is done also for practical reasons. If the canned and sealed saurkraut continued to ferment in cans/jars they would eventually likely explode!

      Additionally, if you are an otherwise healthy person with a working immune system you will probably be fine. People who need to worry are those with, “leaky guts” (for example, someone with Crohn’s disease during an active flare up) or weakened immune systems (such as people under treatment for cancer).

  • I’m a registered dietitian working in a university health centre in oncology. I still remember the first time I received a consult for, “Patient X presenting w/ Lactobacillus septicemia, please assess and advise” and I thought it was a joke! The person, under treatment for leukemia, ended up in the intensive care unit. They were taking probiotics in capsule form to try and boost their immune system.

    We advise against probiotic products in our immuno-compromised patients. The risk of infection appears to be quite rare but there is still little information on safety and efficacy in vulnerable populations.

    We have had a handful of patients develop complications through probiotic use but have not published any case reports to my knowledge.

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