Hippocrates may have been onto something over 2000 years ago. No kidding!
You've probably heard/read about the benefits of the bowel flora/microbiome on your digestive health, and even immune health. However there is an emerging and very interesting body of research exploring the effect of these little guys on our neuropsychiatry, neurotransmitter function and therefore our mood and behaviour. While you think you exhibit free will, in fact you are controlled by the 2kg of commensal microbes in your bowel. In the words of the Borg, ""Resistance is futile!"
These effects have been clearly shown in mouse models where the pre and probiotic environment is manipulated to produce varying behaviours in lab animals. Eg Lactobacillus rhamnosus stimulates the vagus nerve, improving better outcomes in depressed mice.
In a study recently published in Nature, scientists observed changes in the microbiome diversity after stressing a group of mice. When they transplanted the microbes from the stressed mice into sterile calm mice, those mice started exhibiting the same stressed behaviours. This is remarkable because it demonstrates the direct of the gut on the brain (not vice versa).
We might be what we eat and what we think!
Some fields of psychiatry already acknowledge the effect of microbiome imbalances or pathogenic bacteria can directly correct behaviours/conditions such as attention deficit disorder, depression and obsessive compulsive disorder.
Well resistance might be futile but through dietary changes, erradication of pathogenic microbes and supplementation with specific strains, we can favourably alter the populations of bugs in our microbiome and maybe, even our thoughts!