Your Brain on Intestinal Bacteria

I got back from the UK on Sunday night.  I had a wonderful time talking helminths with practitioners from all over the world at the International Congress on Naturopathic Medicine…and of course, having a pint in the pub!


With one of my BFFs, Marc.  (And yeah, ok – I’m only having a half pint.  I’m a lightweight!)


Now I feel overwhelmed in that I have so much to catch you all up on, in terms of biome research. Honestly, who’d have thought even a few years ago that so much could happen in just one week in the world of our intestinal old friends!

So, to pick one of the high points:

A new study[i] was just published looking at how the composition of the gut microbiota affects human emotions.  Researchers at the University of California took fecal samples from 40 healthy women between 18 and 55 years old.  They noted that the microbiota composition fell into 2 distinct groupings, with one have more Bacteroides species and the other having more Prevotella species.  The women were giving MRIs to examine their emotional responses while looking at pictures designed to provoke positive, negative or neutral emotions.

The group with more Bacteroids had thicker grey matter in their frontal cortex, which is the area of the brain that processes complex information.  They also had a larger hippocampus, which is your memory center.  (It’s the area of the brain most affected in Alzheimer’s.)  The women with more Prevotella had a smaller frontal cortex and hippocampus, and showed greater connections between emotional, attentional and sensory regions of the brain. This latter group reported “greater levels of anxiety, distress and irritability when looking at negative images.”[ii]

The authors of the paper point out that the hippocampus regulates emotions, so with it being smaller in the Prevotella group, they may have less ability to contain emotions:  “Reduced hippocampal engagement to negative imagery may be associated with increased emotional arousal.”

The implications of this are obviously tremendous, especially when you consider the staggering rates of “mental illness” in the industrialized world, ranging from depression and anxiety disorders to autism.  This is possibly the first time that gut microbiota have been proven to affect not only the physical composition of the brain, but how humans think and feel.  Amazing!


[i] Tillisch, K, et. al. Brain structure and response to emotional stimuli as related to gut microbial profiles in healthy women.  Psychosomatic Medicine. 2017. doi: 10.1097/PSY.0000000000000493


Leave a Reply

%d bloggers like this: