A recently concluded study in the Netherlands provides evidence for the first time suggesting that probiotic use could help decrease negative thoughts associated with sadness.

In a randomized controlled trial, 40 healthy participants, not diagnosed with any depressive disorder, were given either a probiotic with a variety of bacteria or an inert placebo with only cornstarch and maltodextrins. The participants consumed their probiotics once a day over a period of 28 days. Each participant filled out a questionnaire before and after the trial. The questionnaire dealt with the following feelings (as given in the publication): 

• Aggression (e.g., When I feel down, I lose my temper more easily);
  
• Hopelessness/Suicidality (e.g., When I feel down, I more often feel hopeless about everything; When I feel sad, I feel more that people would be better off if I were dead);
  
• Acceptance/Coping (e.g., When I am sad, I feel more like myself);
  
• Control/Perfectionism (e.g., I work harder when I feel down);
  
• Risk aversion (e.g., When I feel down, I take fewer risks);
  
• Rumination (e.g., When I feel sad, I more often think about how my life could have been different).

Analysis of data revealed that:

• Probiotics had a positive effect on negative thinking patterns (cognitive reactivity)
  
• Probiotics reduced aggressive thoughts
  
• Probiotics also reduced ruminative thoughts (a focus on symptoms of distress, not solution to the problem)
  
• The strongest effects were observed on aggression and rumination.

The human gut is often referred to as the “second brain” and the only organ that possesses its own independent nervous system. Gut bacteria are reported to aid in digestion and also secrete neurochemicals such as serotonin. It is these neurochemicals that the brain uses to regulate an array of functions including learning, memory, and mood. Experiments have been conducted in mice to show that this communication occurs via the vagus nerve, which runs all the way from the brain to the abdomen. 

Probiotics, which include yogurt, yeast, certain cultured milk products, etc., contain live microbes. They are gaining a reputation as a natural way of keeping one’s gut healthy, as they tend to improve host health by stimulating the growth of select bacterial species in the colon. 

The gut-brain axis is being studied in detail, and there are reports of positive effects of probiotics on the mood. The authors of the study discussed here state that their “…findings provide information on a cognitive mechanism that may be responsible for the positive mood effects of probiotic supplementation.”

Written by Mangala Sarkar Ph.D.

Primary Reference:

Steenbergen, L., Sellaro, R., Hemert, S., Bosch, J., & Colzato, L. (2015). A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood. Brain, Behavior, and Immunity. doi:10.1016/j.bbi.2015.04.003

Additional References:

Mayer, E., Knight, R., Mazmanian, S., Cryan, J., & Tillisch, K. (2014). Gut microbes and the brain: Paradigm shift in neuroscience. Journal of Neuroscience, 34(46), 15490-15496.

Forsythe, P., Sudo, N., Dinan, T., Taylor, V. H., & Bienenstock, J. (2010). Mood and gut feelings. Brain, behavior, and immunity, 24(1), 9-16.

Gut Bacteria Might Guide The Workings Of Our Minds. (n.d.). Retrieved April 23, 2015, from http://www.npr.org/blogs/health/2013/11/18/244526773/gut-bacteria-might-guide-the-workings-of-our-minds

Sarkar, M. (n.d.). Gut Feeling: A Scientific Basis? Retrieved April 23, 2015, from http://www.dovemed.com/current-medical-news/gut-feeling-scientific-basis/

Food Insight. (n.d.). Retrieved April 23, 2015, from http://www.foodinsight.org/Functional_Foods_Fact_Sheet_Probiotics_and_Prebiotics

Tillisch, K. (2014). The effects of gut microbiota on CNS functions in humans. Gut Microbes, 5(3), 404-410.