The “gut-brain axis” opens up a whole world of possibilities. If the brain talks to the gut (I’m anxious!) then maybe the gut talks back. New research into what are known as “psychobiotics” suggests that bacteria in the gut can indeed change cognition and emotion.
One example: In a report in Proceedings of the National Academy of Sciences, researchers, led by Javier A. Bravo and Paul Forsythe, fed mice a broth laced with a strain of Lactobacillus rhamnosus. The mice were less likely to be anxious or stressed; also less stress hormone corticosterone was produced as compared to control mice that drank a bacteria-free broth.
The scientists suggest that the gut bacteria normalize the expression of important neurotransmitters in the brain that would naturally be turned up or turned down when animals become stressed or anxious. They looked at the neurotransmitter GABA, the main calming and inhibitory neurotransmitter in the brain.
One of the authors, John Cryan discussed with National Public Radio how the gut influences the brain, and whether the same might hold true in humans:
“And what we found was that this bacteria was able to affect the receptors, which are the proteins in the brain that signal the chemicals, so they affected the levels of these receptors…. But it is one of these things that we were quite surprised at, that we were able to get such a pronounced effect and similar effects as if the animals had been given some pharmaceutical agents that are used to treat anxiety and depression.”
Cryan continued: “The effects on behavior were very similar to what we would see if we’d given these mice an acute injection of valium, yeah. “
“… what’s really neat about this and what’s important to reinforce, as well, is that the mechanism that we’re showing, in terms of what it’s doing to the brain and brain chemistry, is the same as what the pharmaceuticals are doing. So it’s not undermining the actual biology theories underlying anxiety or depression in any sense. It’s just showing that we can modulate them by maintaining good digestive health.”
Now researchers are asking whether probiotics may affect human response to sad mood. Laura Steenbergen and colleagues reported their results in a paper titled “A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood”
- 20 healthy individuals without current mood disorder received multispecies probiotic for 4-weeks
- 20 healthy individuals without current mood disorder received placebo for 4-weeks
Strains of the following were mixed:
- Bifidobacterium bifidum
- Bifidobacterium lactis
- Lactobacillus acidophilus
- Lactobacillus brevis
- Lactobacillus casei
- Lactobacillus salivarius
- Lactococcus lactis
Pre and post study assessments used the Leiden index of depression sensitivity scale.
Probiotics reduced cognitive reactivity to sad mood. Did probiotics reduce the sadness? No, the study showed the probiotics reduced the response to sad moods. Aggressive thoughts and rumination were the usual negative responses associated with sad mood.
These reactions are patterns of thinking which lead to depression. Handling or coping with a sad mood, which is normal and part of being human, without resorting to a cascade of negative thinking is a prime goal in maintaining mental health. Read this important paper. It also gives a good overview of research to date on this topic.
Depression is increasing worldwide and strong medications are the popular answer. But other solutions such as a healthy gut would be far safer.