How your gut bugs can chill you out or stress you out
Robyn Chuter – Naturopath
Anxiety is a modern epidemic. In the last major population study of mental health conducted in Australia, the 2007 National Survey of Mental Health and Wellbeing, anxiety disorders were found to be the most common psychological conditions affecting Australian adults.
In fact, 14% of all people aged 16-85 years reported that they had experienced an anxiety disorder in the 12 months prior to interview. Females report more anxiety than males: 18% of females vs 11% of males admitted to having experienced an anxiety disorder in the previous 12 months.
While many theories have been advanced to explain why we are more anxious today than we’ve ever been, despite our lives being infinitely safer, more comfortable and less physically challenging than at any prior stage in human history, one factor hasn’t received much popular attention: the role that our gut bacteria may be playing in anxiety and other mental health issues.
There are approximately 100 trillion (that’s 100 000 000 000 000!) microorganisms inhabiting the human gut. We depend on this teeming population of resident microorganisms to break down components of food that we can’t digest, produce vitamins, help us absorb minerals, shape and regulate our immune system, fend off infectious organisms, metabolise drugs, chemicals and our own metabolic waste products, regulate the movement of food and waste through our intestinal tract, and a host of other tasks that are critical to our well-being.
And, apropos of the topic of this post, our gut bacteria also talk – and listen – to our brains, by using a wide variety of hormones, neurotransmitters and other chemical signals.
This ongoing conversation between our brains and our gut bugs – known as the gut-brain axis – impacts them both. For example, psychological stress affects both the composition and functioning of the gut microbiota. And in turn, alterations in the composition of the gut microbiota affects our brain function, including our emotional experiences.
Here are some of the mechanisms by which our gut bacteria can either induce, worsen or relieve our feelings of anxiety:
- Gram negative bacteria, which thrive when their human hosts eat a diet high in fat and/or animal protein comprise, all contain a substance called endotoxin in their outer membranes. They release this endotoxin when they die or break down. Elevated levels of endotoxin cause ‘leaky gut’ which then results in endotoxin getting into our bloodstream – a condition known as ‘endotoxaemia’. Endotoxaemia produces a pronounced increase in anxiety, and the more anxious people tend to be in general, the more ramped-up their anxiety becomes when their blood levels of endotoxin rise.
- On the other hand, butyrate-producing bacteria thrive when we eat a diet rich in the kinds of carbohydrates that humans can’t digest – particularly fibre and resistant starch. Butyrate helps to ‘heal and seal’ leaky gut, decreases endotoxin absorption through the gut wall, regulates inflammation not only in the gut itself but throughout the entire body – including the brain – and stimulates the release of brain-derived neurotrophic factor (BDNF), dubbed ‘miracle grow for brain cells’; some studies have found that BDNF levels are reduced in people suffering from anxiety.
- Certain microbiota species are able to produce neurotransmitters, including GABA (dubbed ‘nature’s Xanax’ for its calming effects) and serotonin, which is associated with positive mood.
- Specific probiotic strains have been found to reduce anxiety symptoms, including Bifidobacterium longum R0175, Lactobacillus helveticus R0052 and Lactobacillus rhamnosus HN001.
- Regular exercise results in increased numbers of butyrate-producing gut microbes, which helps to explain why exercise has such beneficial effects on anxiety.
In summary, if you’re prone to anxiety, you’d be well-advised to choose a dietary pattern and lifestyle that nurtures anxiety-reducing gut microbes and reduces the proliferation of bugs whose activities increase anxiety.
That means a diet rich in fibre- and resistant starch-rich whole and minimally processed plant foods: fruits, vegetables, whole grains, legumes, seeds and nuts. Keep fat intake low, and limit or eliminate animal products.
And build regular physical activity into your routine – preferably outdoors.