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

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 3 g solid content and 283.5 μg 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 0.267 g solid content and 22.5 μg of DHNA) for a period of 13 weeks. 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.