The right gut bacteria can make you more or less stressful, and perhaps more or less clever too:
And now evidence is emerging that these tiny organisms may also have a profound impact on the brain too. They are a living augmentation of your body – and like any enhancement, this means they could, in principle, be upgraded.
His team tested the effects of two strains of bacteria, finding that one improved cognition in mice. His team is now embarking on human trials, to see if healthy volunteers can have their cognitive abilities enhanced or modulated by tweaking the gut microbiome.
— BBC, Body bacteria: Can your gut bugs make you smarter?, via Slashdot, Gut Bacteria Affect the Brain.
Apparently a very monotonous diet reduces the variety of gut bacteria. I’m just waiting to hear that processed food was a long-term Communist plot to make us dumber.