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Sunday, 08 April 2018 22:29

Purported Paraprobiotic Potential - BacterioFiles 335

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Published in Bacteriofiles

This episode: Paraprobiotics, or killed probiotic bacteria, are studied for health effects, but results and study design are questionable!

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(11.5 MB, 12.6 minutes)

Show notes: 

bf335lactoMicrobe of the episode: Phlox virus S

Journal Paper:
Nishida K, Sawada D, Kawai T, Kuwano Y, Fujiwara S, Rokutan K. 2017. Para-psychobiotic Lactobacillus gasseri CP2305 ameliorates stress-related symptoms and sleep quality. J Appl Microbiol 123:1561–1570.

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Episode outline:

  • Background: Probiotics: WHO def is “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host”
    • Many benefits claimed, depending on organism and other conditions
    • Not all show benefit once going from lab animal studies to humans, or in replication
    • Complicated to study: have well-defined test group, genotype, cell status, delivery, dose
  • But evidence building that benefit doesn’t always require live microbes
    • Pieces of probiotics might be sufficient at least for some benefits
    • These treatments called “paraprobiotics”
    • Could be easier to study and more shelf-stable to deliver
  • What’s new: Now, scientists publishing in the Journal of Applied Microbiology have looked into some possible stress-reducing effects of a type of killed probiotic bacterium!
  • Lactobacillus gasseri CP2305, previously found some benefits in volunteers when live or killed
  • Methods: Recruited 2nd-year medical students in Japan as chronic stress model
    • Healthy but taking course in cadaver dissection
  • Gave either fermented milk, sterilized by heat, or placebo of lactic acid-soured milk beverage
    • Confirmed indistinguishable by test panels
    • Consumed daily
    • Then assessed general health, depression, anxiety, and sleep with questionnaires
      • Also gut symptoms and eating disturbances
      • Sig level of 0.05
    • And tested saliva for cortisol and other stress-related indicators
    • And use sequencing to check gut microbiota
  • General Health Questionnaire: lower scores are better
    • Paraprobiotic group scores didn’t change
    • Placebo group scores increased from ~18 to 20
    • However: treatment scores started out higher on average, statistics not impressive
      • Scores significantly different for women, not for men or all together
      • Could be sex difference
  • Sleep quality: here, scores improved for treated men and overall but not women
    • No other differences in general health questionnaires
  • Diarrhea: no significance except in men
  • No effects in salivary markers
  • Some changes in microbiota though, with treatment
    • Bacteroidetes phylum decreased
    • A couple genera changed, and 15 species
    • Nothing jumps out at me
    • Would've been helpful to do functional analysis of proteins and such, but hard
  • Summary: Giving inactivated probiotic bacteria didn't seem to have much effect on stressed medical students
  • Clarifications if necessary: Statistics were just t-tests
    • no indication of multiple comparisons correction
  • All questionnaire measures: treatment group started out higher
  • Says double-blind but no details given, just have to take their word
  • 2/6 authors from Asahi Group Holdings company that have milk-related products called Calpis or Calpico
    • Though claim no conflicts of interest
  • What do I think: Anyone doing probiotics research needs to hold to higher standards
    • Wouldn't say it's not worth researching, still value
      • Probiotics and also paraprobiotics
    • But so much junk already, gotta work hard to set quality apart
  • Perhaps more regulation of commercial probiotics could reduce motivation to low-quality?
  • Science self-correcting, find out truth in the end
Last modified on Sunday, 08 April 2018 22:39
Jesse Noar

Jesse Noar is microbiologist with a PhD from North Carolina State University and Bachelor's from Cornell. Most of his research has focused on the amazing abilities and potential uses of bacteria, especially those found in soil. Jesse hosts the BacterioFiles podcast highlighting the most interesting recent microbiology research on all kinds of different microbes, part of the ASM family of podcasts. Learn more at or at