Safety of high doses of Propionibacterium freudenreichii ET-3 culture in healthy adult subjects

Regul Toxicol Pharmacol. 2011 Jul;60(2):262-7. doi: 10.1016/j.yrtph.2010.12.005. Epub 2010 Dec 21.


Propionibacterium freudenreichii ET-3 (7025) culture, a cell-free product of whey fermentation by P. freudenreichii ET-3, has been shown to promote the growth of Bifidobacteria through the action of 1,4-dihydroxy-2-naphthoic acid (DHNA). Here we report the results of two clinical studies designed to evaluate the safety of high doses of P. freudenreichii ET-3 culture medium. Study 1 had a randomized, double-blind, crossover design. Ten healthy male and four healthy female subjects received 45 tablets of either P. freudenreichii ET-3 culture medium (total daily intake of 3g solid content and 283.5μg of DHNA; active group) or placebo (unfermented product) during two 1-week supplementation periods separated by a 4-week washout period. In Study 2, 11 healthy men took four tablets of P. freudenreichii ET-3 culture medium per day (total daily intake of 0.267g solid content and 22.5μg of DHNA) for a period of 13weeks. In both studies, hematological, clinical chemistry, and urinary parameters were measured before and after each supplementation period and gastrointestinal symptoms were assessed by questionnaire. In Study 1, there were no statistically significant differences between placebo and active supplementation periods in any measured parameter and the incidence of gastrointestinal symptoms were similar between groups. In Study 2, total protein, white blood cell count, hemoglobin, and mean corpuscular hemoglobin concentration decreased significantly from baseline and mean corpuscular volume and urine pH increased from baseline. The changes in hematological parameters were deemed not to be due to P. freudenreichii ET-3 culture medium supplementation given that all parameters remained within normal ranges and were not consistent with any clinically meaningful effect.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Bifidobacterium / growth & development
  • Cross-Over Studies
  • Culture Media
  • Dietary Supplements / adverse effects*
  • Double-Blind Method
  • Female
  • Fermentation
  • Humans
  • Male
  • Middle Aged
  • Naphthols / administration & dosage
  • Naphthols / adverse effects*
  • Propionibacterium / metabolism*
  • Surveys and Questionnaires
  • Tablets
  • Young Adult


  • Culture Media
  • Naphthols
  • Tablets
  • 1,4-dihydroxy-2-naphthoic acid