The bacteria in our guts can influence the working of the mind, says
Frank Swain. So could they be upgraded to enhance brainpower?
I have some startling news: you are not human. At least, by some
counts. While you are indeed made up of billions of human cells working
in remarkable concert, these are easily outnumbered by the bacterial cells that live on and in you
– your microbiome. There are ten of them for every one of your own
cells, and they add an extra two kilograms (4.4lbs) to your body.
Far
from being freeloading passengers, many of these microbes actively help
digest food and prevent infection. 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. So, could you hack
your microbiome to make yourself healthier, happier, and smarter too?
According
to John Cryan, this isn’t as far-fetched as it sounds. As a professor
of anatomy and neuroscience at University College Cork, he specialises
in the relationship between the brain and the gut. One of his early
experiments showed the diversity of bacteria living in the gut was
greatly diminished in mice suffering from early life stress. This
finding inspired him to investigate the connection between the
microbiome and the brain.
The bacterial microbiota in the gut
helps normal brain development, says Cryan. “If you don’t have
microbiota you have major changes in brain structure and function, and
then also in behaviour.” In a pioneering study, a Japanese research team
showed that mice raised without any gut bacteria had an exaggerated
physical response to stress, releasing more hormone than mice that had a
full complement of bacteria. However, this effect could be reduced in
bacteria-free mice by repopulating their gut with Bifidobacterium infantis,
one of the major symbiotic bacteria found in the gut. Cryan’s team
built on this finding, showing that this effect could be reproduced even
in healthy mice. “We took healthy mice and fed them Lactobacillus
[another common gut bacteria), and we showed that these animals had a
reduced stress response and reduced anxiety-related behaviours.”
When this bacteria was fed to mice it reduced stress and anxiety (Science Photo Library)
But why should bacteria in the gut affect the brain? There are
several different ways that messages can be sent from one organ to the
other. It can be hormones or immune cells via the bloodstream, or by
impulses along the vagus nerve, which stretches from the brain to
intertwine closely with the gut. Through these pathways, actions in one
produce effects in the other.
So how might you go about altering
your microbiome to do a spot of brain-hacking? Cryan’s team works on
several fronts, investigating the potential to manage stress, pain,
obesity and cognition through the gut. “We have unpublished data showing
that probiotics can enhance learning in animal models,” he tells me.
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.
Another method of
adjusting the bacterial profile of your gut is to undergo a transplant
that involves taking faecal material from a donor’s intestine – often a
close relative – and implanting into a recipient via enema infusion.
This unorthodox treatment has been shown to successfully treat
infections caused by pathogenic bacteria colonising the gut.
Brain boost
Thankfully,
Cryan has a far more appetising method on offer. “Diet is perhaps the
biggest factor in shaping the composition of the microbiome,” he says. A
study by University College Cork researchers published in Nature in 2012
followed 200 elderly people over the course of two years, as they
transitioned into different environments such as nursing homes. The
researchers found that their subjects’ health – frailty, cognition, and
immune system – all correlated with their microbiome. From bacterial
population alone, researchers could tell if a patient was a long-stay
patient in a nursing home, or short-stay, or living in the general
community. These changes were a direct reflection of their diet in these
different environments. “A diverse diet gives you a diverse microbiome
that gives you a better health outcome,” says Cryan.
Beyond a
healthy and varied diet, though, it still remains to be discovered
whether certain food combinations could alter the microbiome to produce a
cognitive boost. In fact, Cryan recommends that claims from probiotic
supplements of brain-boosting ought to be taken with a pinch of salt for
now. “Unless the studies have been done, one can assume they’re not
going to have any effect on mental health,” he says. Still, he’s
optimistic about the future. “The field right now is evolving very
strongly and quickly. There’s a lot of important research to be done.
It’s still early days.”
Hacking the brain often conjures up ideas
of electrical hardware such as implants and trans-cranial stimulators.
But it might be the case that a simple change in diet can shift your
brain up a gear. The transhumanists and body hackers who believe that
technology is the sole way to improve human ability would do well to pay
as much attention to the living augmentation that already resides in
their gut.
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