BioProject

Background: The bidirectional relationship between the human gastrointestinal tract and the brain has been the focus of recent research, particularly its intersection with mental wellbeing. More...

Background: The bidirectional relationship between the human gastrointestinal tract and the brain has been the focus of recent research, particularly its intersection with mental wellbeing. Depression is the leading cause of disability worldwide, with evidence suggesting that decreased gut barrier function and inflammation are correlated with depressive symptoms. This study explored whether regular consumption of probiotic supplements (Winclove’s Ecologic® Barrier), led to a reduction in depressive symptoms in a sample of participants with a range of symptom severity. The composition of the gut microbiota was additionally monitored to determine any corresponding changes.Method: 71 participants with mild to severe depressive symptoms were randomly allocated to two groups and consumed either a probiotic or placebo supplement daily over eight weeks. Pre- and post-intervention measures of symptoms and vulnerability markers of depression and gut microbiota composition were compared. Participants in the clinical trial were also compared on psychological variables and gut microbiota composition to a non-depressed group (n = 20).Results: Clinical trial results indicated that regardless of group allocation, all participants demonstrated improvement in symptoms, suggesting non-specific therapeutic effects associated with weekly monitoring visits. Participants with mild and moderate levels of depression who consumed the probiotic demonstrated a significantly greater reduction in cognitive reactivity towards sad mood (a vulnerability factor for depression) compared to the placebo group. Probiotics did not significantly alter the overall microbiota of depressed individuals after consumption. Looking specifically at the bacterial genera within the probiotics, only the Lactobacillus genus showed a significant, but very small increase after probiotic consumption. Additionally, there were only minor differences in the microbiota of depressed individuals pre-intervention when compared to the non-depressed cohort. Ruminococcus gnavus was significantly and positively correlated to the DASS depression score.Conclusions: While microbiota composition was similar between all groups, probiotics did affect a psychological variable associated with susceptibility to depression. Further research is needed to investigate how probiotics can be utilised to modify mental wellbeing, and whether they can act as an adjunct to existing depression treatments.This study was approved by the University of Technology Sydney Human Research Ethics committee, UTS HREC Reference number: 2015000438. The trial was registered in the ANZCTR, Trial ID: ACTRN12615001081505. Less...