Did you know that for each human cell, there are ten – yes, ten – microorganisms in your body? I didn’t, until New Scientist magazine informed me last week. This week, the magazine offers a window into an intriguing new world: that of psychobiotics (pp. 28-29, 25 January 2014 issue).
We’ve all heard about gut bacteria; perhaps many of us have seen advertisements for products claiming to restore the balance of “good” and “bad” bacteria in our digestive systems. As it turns out, gut bacteria not only help us digest our food, but also have an impact on brain chemistry, and therefore on our emotions, mood and behaviour.
For example, mice raised in a completely germ-free environment (therefore without gut bacteria, which enter the body shortly after birth) showed autistic-like behaviours, such as spending as much time focussed on inanimate objects as on other mice. It turns out certain gut bacteria produce some of the neurotransmitters (molecules which send signals between nerves) as our brain does. Examples include dopamine, serotonin and GABA (gamma-aminobutryic acid). Although these neurotransmitters are produced in the gut, the vagus nerve, which connects the gut and the brain, changes the expression of some of these neurotransmitters in the brain. This is one way the seemingly-innocent bugs in the gut can influence our mood.
Other ways the tiny creatures in our abdomen may influence our psychological well-being is by manufacturing short-chain fatty acids, or by altering our immune system.
Researchers are exploring the possibilities that cocktails of good bacteria, or even genetically modified organisms, may one day offer an alternative to more traditional antidepressants.
The article warned that despite marketing claims to the contrary, probiotics available to consumers today have not been proven to have psychotropic effects – in other words, the probiotics you can purchase at a health food store or pharmacy haven’t yet been shown in clinical trials to alleviate depression, anxiety or other mood disorders. I hadn’t actually seen advertising to this effect, but this may be because (a) I’m not heavily into alternative medicine, or (b) because I live in Australia; apparently, the more relaxed laws made it possible for companies to claim psychotropic benefits for probiotics in the US and European Union, until recently. The probiotics currently in the marketplace are not the same strains as those the researchers are studying, and even if small amounts are present in probiotic products, they are apparently eliminated by the acidity of the stomach before reaching the gut.
Still, it’s worth thinking about: one day, we might have little helper creatures living inside us, making us happier, less anxious, and more sociable – all while helping us digest our food. How’s that for multitasking?