Your Gut Bugs, or more scientifically called your microbiota, actually have a say in what goes on in your mind. This link between the bacteria in your digestive system and your mental state is also known as the Gut-Brain Axis. The good news is, more and more research on this connection is emerging at a time when so many people are stuck in an ongoing battle with their mental health.
Tell Me About the Bugs
So they're not actually bugs... the microbiota present in your digestive tract (and many other places in your body) consists of a variety of microorganisms including bacteria. The number of bacteria cells in your body is actually approximately EQUAL to the number of human cells in your body (1). So the ongoing debate continues... are you human, or just a walking haven for bacteria?
You may not be thrilled by the thought of being full of bacteria, but these critters are actually beneficial in your body. The good ones can protect against pathogenic bacteria that cause disease, as well as produce important vitamins that the body cannot make itself such as vitamin K and B12 (2). Interestingly, these bacteria also play a role in the regulation of stress and mood.
The Impacts of Stress
We know that stress does a lot of things to your body, and affecting your microbiota is no exception. Chronic stress may alter the composition of the microbiota as well as cause increased numbers of certain inflammatory substances in the digestive tract (3). These inflammatory substances, called cytokines, are produced by the immune system within the digestive tract. Their impact is to then cause further havoc by resulting in immune reactions elsewhere in the body. Chronic stress may also compromise the integrity of the intestinal walls. This makes it easier for these cytokines, and other inflammatory substances produced by the microbiota, to cross the intestinal wall and enter your blood stream (3).
Anxiety & Depression
Why do we care about these inflammatory cytokines? They can actually influence conditions such as anxiety and depression. Human studies have shown that those with chronic depression have an increased immune response to LPS, an inflammatory substance produced by certain bacteria within the microbiota (4). Furthermore, inflammation within in the digestive tract caused by certain infections, has been shown to induce anxiety-like behaviour in animal models (5, 6). In one of these studies, the anxiety-like behaviour was normalized by administering a particular probiotic (6). Ongoing research aims to determine which intestinal bacteria are correlated with anxiety and depression, with the hopes that by optimizing our microbiota composition we can treat these debilitating conditions.
Many factors influence your microbiota, some of which are relatively easy to do on a day-to-day basis.
Stress Modulation - as talked about above, stress can impact your microbiota in unwanted ways. So regular stress-reduction techniques such as deep breathing, laughing, yoga, meditation, and moderate exercise are good go-tos.
High Fibre Diet - non-digestible, fibrous foods can promote the growth of beneficial bacteria by acting as "prebiotics". Some prebiotic foods include onions, garlic, asparagus, artichoke, leeks, and ground flaxseeds.
Probiotics - these are live bacteria taken in the form of a supplement aimed at populating the digestive tract with good microbiota. They can be particularly helpful in repopulating the microbiota after antibiotic use. More research is needed to determine long term effects of probiotics and which types are most optimal. Talk to your healthcare practitioner before starting probiotics.
1. Sender, R., Fuchs, S., Milo, R. (2016). Revised estimates for the number of human and bacteria cells in the body. PLOS Biology.
2. Kau, A., Ahern, P., Griffin, N., Goodman, A., Gordon, J. (2011). Human nutrition, the gut microbiome, and immune system: envisioning the future. Nature, 474, 327-336.
3. Cryan, J., Dinan, T. (2012). Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour. Nature Reviews, 13, 701-712.
4. Maes, M., Kubera, M., Leunis, J. C., Berk, M. (2012). Increased IgA and IgM responses against gut commensals in chronic depression: further evidence for increased bacterial translocation or leaky gut. J. Affect. Disord. 141, 55–62.
5. Goehler, L., Park, S., Optiz, N., Lyte, M., Gaykema, R. (2008). Campylobacter jejuni infection increases anxiety-like behaviour in the holeboard: possible anatomical substrates for viscerosensory modulation of exploratory behaviour. Brain Behav. Immun., 22(3), 354-366.
6. Berick, P., Verdu, E., Foster, J., Potter, M., Huang, X., Malinowski, P.... Collins, S. (2010). Chronic gastrointestinal inflammation induces anxiety-like behaviour and alters central nervous system biochemistry in mice. Gastroenterology, 139(6), 2101-2112.