The Stress Resilient Mind Blog
Probiotics, Anxiety and Depression
Publication date: 30 July 2013
Recently Dr Mercola (a leading american natural health physician) posted an article on probiotics for anxiety. He reports on a recent small-scale study on the positive effects of probiotics on brain function, and asks, "are probiotics the new prozac?" - might it make more sense to take probiotics for anxiety than the more usual anti-depressants? In this post I consider how it is that probiotics help brain function and why Dr Mercola might be right.
First, some general background. Gut health is vital to brain function. Two broad aspects of gut health in particular: barrier integrity and gut flora (meaning the population of micro-organisms living in the gut).
Barrier integrity - this is to do with the gut's job of absorbing nutrients while keeping out everything else. If the integrity is compromised both these jobs are too. If the barrier becomes leaky, partially digested food and other toxic material can enter the blood supply. There, it taxes the liver (which does your detoxification) and also provokes the immune system to react. In short, added strain on the liver and immune system. Also, toxins may impact the brain.
Gut flora - the balance of micro-organisms (between healthy bugs and harmful bugs) is critical to setting the balance of the immune system. The immune system is spread over the whole body but most cells are in the gut, where they are exposed to the gut flora. An imbalanced immune system can trigger inflammation, allergies and even auto-immune disorders (where the immune system attacks your own cells). Also it stimulates production of the stress hormone cortisol.
The brain is constantly engaged in a two-way communication with the gut, via hormones, nerves and even the immune system (which has its own class of signalling molecules called cytokines).
For example cortisol affects the brain. It's designed to help us cope with stress, but chronically high levels can damage the brain (possibly causing depression) and low levels leave us vulnerable to anxiety. Research suggests probiotics modulate cortisol.
The vagus nerve carries information about the state of the gut to the brain, and also signals from the brain to the gut - in particular it is the output channel of the parasympathetic nervous system which transmits the relaxation response. Research suggests probiotics modulate vagal signalling.
Another line of research suggests that probiotics alter GABA levels in the brain. GABA is the brain's main inhibitory (or calming) neurotransmitter. GABA may be deficient in anxiety sufferers - several anti- anxiety medications seem to work by boosting GABA levels.
There's a theory that depression and other mental health disorders may be caused by (or mediated by) inflammation within the brain.
Probiotics may improve gut barrier integrity by reducing inflammation in the gut, thus reducing the toxic and inflammatory strain on the whole body (including the brain).
Probiotics may also benefit the health of the gut flora - but you also need to know that what you eat determines the health of the gut flora too. Sugar, for example, tends to feed the bad guys.
Many of my clients suffer from anxiety, low mood, and problems with focus and concentration. Very often these same people have gut problems such as bloating or IBS. As a nutritional therapist I often recommend probiotics to my client to support their gut function. It's good to know they may be having beneficial effects well beyond the gut.
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