A couple of months back I posted an article where I discussed a scientific paper linking the gut microbiota to food cravings and appetite, and I posed the question: Who’s in control: The human host or the microbiome? A decade ago, relatively little was known about the trillions of tiny organisms occupying our bodies, and few considered the possibility that gut bacteria could somehow control our behaviour and brain function. Fast forward 10 years, and a lot has changed. Recent research on the microbiome-gut-brain axis has made it clear that gut microbes affect our mental health through several different pathways (e.g., production of neurotransmitters, gut barrier function/inflammation), newspapers and magazines now routinely publish articles on the relationship between intestinal bacteria and mental illnesses, and some would probably go as far as to say that the answer to the question I posed in the previously mentioned article is the microbiome.
Far-reaching public health implications
The growing pile of evidence connecting the gut microbiome to mental health has broad implications for nutrition, health, and medicine. Perhaps most importantly, it’s becoming increasingly clear that diet – and all of the other factors that shape the human microbiome – should play a much greater role in the discussion and treatment of mental illnesses. As Dr. Natasha Campbell-McBride says in her book “Gut and Psychology Syndrome”, the majority of patients with ADHD, autism, and a wide range of other mental health disorders have a dysbiotic gut microbiota – a statement that’s supported by recent research linking alterations of the gut microbiome to mental illnesses (1, 2, 3).
One the one hand, the newfound information in this area empowers us in the sense that we now realise that we can improve our mental health by manipulating the microbiome through diet, probiotics, prebiotics, etc.
On the other hand, we’re starting to realise that we’ve been setting ourselves up for failure in the sense that modern living environments – which are markedly different from those our hominin ancestors evolved in for millions of years – aren’t exactly “microbiome friendly”. In my mind, there’s no doubt that the increased prevalence of mental health problems such as depression, ADHD, and autism over the last couple of decades can partly be attributed to the destructive impact of modern diets and lifestyles on the human microbiome.
Besides the role of birth mode, infant feeding practises, diet, pharmaceutical use, and all of the other things that shape the microbiome throughout life, genetics also plays a role in determining the make-up of the microbiome. Accumulating evidence shows that our environment can be “passed on” to our offspring through epigenetic tags. Let’s take inflammatory bowel disease for example, which has increased in prevalence lately (4). Ulcerative colitis and Crohn’s disease are known to have a genetic component. However, our genes haven’t changed much over the last couple of centuries, suggesting a possible role for epigenetics. In other words, there might be underlying epigenetic reasons for why some people with severe gut dysbiosis, like what’s seen in IBD, aren’t able to permanently repair their microbiome.
Another problem at the moment is that although there are many possible strategies you can use to achieve a healthier microbiota, cheap, easy, and effective solutions to repairing a broken gut ecosystem are still lacking. However, this will hopefully change in the near future. Researchers are now looking into the potential of psychobiotics, which are live organisms that, when ingested in adequate amounts, produce a health benefit in patients suffering from psychiatric illness, and soon, microbial cocktails might be a natural part of the treatment regime for many different health conditions.
Clearly, the gut microbiome isn’t the only factor to consider in the discussion of mental health – far from it – but it’s definitely emerging as an important player.
How our thoughts and emotions are connected to our guts
Today, instead of writing another long article on the microbiome, I wanted to share a recent Ted Talk by John Cryan, a neuropharmacologist and microbiome expert from the University College Cork. In the talk, Dr. Cryan explores the connection between our thoughts and emotions and our gut bacteria and takes a look at some of the recent research in this area.
What are your thoughts on the relationship between gut bacteria and mental health? How do you feel about the fact that bacteria affect your mood, behaviour, and thoughts?