There has been much recent talk about the ‘gut-microbiome-brain axis’ which describes the way our gut, gut bacteria (microbiome), and our brain communicate with one another.
Sometimes called the second brain, the gut is implicated in mood disorders such as depression and anxiety. Moreover, people experiencing mood issues often present with gut issues too, such as IBS.
Consequently, much attention has been drawn to how we can influence gut bacteria through diet and lifestyle, including supplementation with probiotics (live strains of friendly bacteria and/or yeasts).
How does my gut and brain interact?
There are several routes by which your gut and brain communicate with each other, however, most researchers currently believe the primary route is via the vagus nerve.
The vagus nerve is a widely distributed nerve that travels from your head right down to your abdomen and serves to control your heart, lungs, and digestive tract.
Communication is a two-way street, with feedback being passed from your digestive system to your brain and back again in a continual conversation.
It is thought that this communication is influenced by 3 things:
The composition of your gut bacteria (friendly & unfriendly)
How well your gut lining is functioning
Your hormones, neurotransmitters, immune system, and chemical messengers that are present in your gut and interact with nerve cells.
Probiotics & inflammation
Research has suggested that probiotics can reduce gut inflammation. One way that this can happen is by the ability of some species to positively dampen down inflammatory immune responses within your digestive tract.
Inflammation can translocate from your gut and enter circulation, creating damage to tissues, including organs such as the brain, which can then impact its function. Inflammation is a leading modern theory in mood disorders such as depression and anxiety, and there is much interest in how the immune and nervous systems interact with each other.
Probiotics & gut lining integrity
A disrupted gut barrier can often be observed in people with mood disorders, including anxiety and depression.
The intestinal barrier is a specialised lining in your intestines that allows the absorption of nutrients, whilst preventing toxins and other unwanted substances from entering your circulation. A breakdown of this lining (‘leaky gut’) can permit entry of such substances, alerting your immune system and triggering inflammation.
Friendly bacteria in the gut play an important role in preserving the integrity of the gut lining and probiotics may therefore assist with protecting it from damage.
Probiotics & neurotransmitters
Studies have shown that gut bacteria can impact neurotransmitter production and their signaling between nerve cells.
This means that neurotransmitters such as serotonin, often thought to be low in mood disorders, could be enhanced with friendly bacteria. Increasing evidence has demonstrated that the health of your digestive tract has a direct impact on mood. For instance...
your gut bacteria are responsible for the production of 95% of your body’s serotonin.
Friendly bacteria help to promote good gut health and a well-functioning gut, and a well-functioning gut can promote optimum neurotransmitter production and signaling
This means that there might be a place for probiotics in enhancing neurotransmitter production.
Research on mental health and probiotics is ongoing, however, species of Lactobacillus and Bifidobacterium are generally thought to be beneficial. Generally, when selecting a probiotic, it seems to be better to take a multi-species strain which is also combined with a prebiotic.