The human intestines house an astonishing number, and species, of microorganisms (microbiota), most of which live in the colon. The exact number is still being debated but we have a lot of them and they play an intimate role in well-bring, not the least of which is their role in regulating mental health and mood via the gut-brain-microbiota axis. Although each person’s microbial profile is distinct, the relative abundance and distribution of bacterial species is similar among healthy individuals which help maintain overall health. Since the gut and the brain communicate bidirectionally, the health of the gut, including the gut bacteria, influences our mood and anything that can help support a healthy gut bacterial profile, like probiotics, might help support mental health which is exactly what was found in a study looking at probiotic supplements and depression.
Probiotics helped depression
This 2017 study from the Journal of Gastroenterology demonstrated that by supporting the gut and the gut’s bacterial residents, objective measures of depression can be improved. What many don’t know, is that many of the neurotransmitters that influence mood are produced in the gut including serotonin (90%), and dopamine (50%).
Researchers at McMaster University in Hamilton, Canada looked at a specific strain of bifidobacterium (genus) longum (species) to see whether or not it would improve depression. They looked at 44 adults with IBS and diarrhea or a mixed-stool pattern (based on Rome III criteria) and mild to moderate anxiety and/or depression (based on the McMaster Hospital Anxiety and Depression scale).
Patients were randomly assigned to either a daily placebo (dummy pill) or Bifidobacterium longum NCC3001
At weeks 0, 6, and 10, researchers determined the patients’ levels of anxiety and depression, IBS symptoms, quality of life, and somatization [or the subjective perception of medical symptoms without any evidence they exist] using validated questionnaires. They also assessed brain activation patterns, fecal microbiota, urine metabolome profiles, serum markers of inflammation, neurotransmitters, and neurotrophin levels.
In other words, they conducted a well designed study to measure depression, as well as, other objective physical indicators of improvement on mental health including mood.
What did they find?
An impression 64% of patients taking the Bifidobacterium longum NCC3001 supplement saw a significant reduction in their depression compared to 34% of those taking the placebo. But that’s not all, despite not having improvements on anxiety or IBS symptoms, those in the probiotic group still had improvement in the quality of life score compared to placebo. This makes sense as we’d expect anyone with less depression to have a better overall sense of their quality of life as their perception & outlook would be changed.
What’s also interesting is that the MRI analysis showed that the probiotic group had reduced responses to negative emotional stimuli in multiple brain areas [amygdala and fronto-limbic regions were less active], compared with placebo which shows that the probiotic positively influenced the gut which, in turn, benefit the brain and brain activity (via the gut-brain-microbiota axis).
And the benefits were still present 4 weeks after the end of the study; depression scores were still reduced/improved
What’s the bottom line?
There are many things that influence mood, not just the health of our guts and the type of bacteria we carry around. When it comes to probiotics, several different bacteria types have been looked at. While this study specifically examined the species NCC3001, other bifidobacterium longum species have been studied in both humans and animal models (1, 2, 3, 4 and 5). Other bifido strains may have different effects compared to the strain used in the above study, we’re not entirely sure, but taking a probiotic supplement with different bifidobacterium longum species may be worth trying though; they have a very good safety record but be sure to speak to a health care practitioner if you have any questions.