Low serum enterolactone concentration is associated with low colonicLactobacillus–Enterococcuscounts in men but is not affected by a synbiotic mixture in a randomised, placebo-controlled, double-blind, cross-over intervention study

Abstract

The aims of the present study were to assess the possible differences in faecal microbiota between men with a low serum enterolactone concentration and those with a high concentration, and to investigate the impact of a synbiotic mixture on serum enterolactone concentration in men with a low concentration. We compared faecal microbiota between ten men with the lowest serum enterolactone concentration and ten men with the highest concentration at recruitment (n84). Furthermore, we carried out a randomised, double-blind, placebo-controlled, cross-over intervention study (6-week intervention periods and 4-week washout period) to investigate the impact of a synbiotic mixture (twoLactobacillusstrains, oneBifidobacteriumstrain, onePropionibacteriumstrain and galacto-oligosaccharides (32 g/l)) on serum enterolactone concentration in fifty-two men who had a concentration < 20 nmol/l. Serum sensitive C-reactive protein (CRP) concentration was measured at the end of the first intervention period. Men with a low serum enterolactone concentration when compared with those with a high concentration had less faecal bacteria, especially those belonging to theLactobacillus–Enterococcusgroup (median 8·2 (interquartile range 7·8–8·4) log10colony-forming units/gv.median 8·8 (interquartile range 8·5–8·9) log10colony-forming units/g,P= 0·009). The synbiotic mixture that was used did not have a significant effect on serum enterolactone (synbioticv.placebo ratio 0·96 (95 % CI 0·76, 1·22),P= 0·724) or serum sensitive CRP (synbioticv.placebo ratio 0·99 (95 % CI 0·74, 1·33),P= 0·954) concentration. Men with a low serum enterolactone concentration harbour less colonic bacteria, especially those belonging to theLactobacillus–Enterococcusgroup. A synbiotic mixture does not increase serum enterolactone concentration.