The Unexpected Connection with Our Gut and Mental Health


“All disease begins in the gut.” -Hippocrates (450 BCE to 380 BCE)

Leading edge in science is re-discovering that our brain and mental health are influenced by what goes on in the gut (e.g., Kaplan et al. 2015). Yet, if you stop to think about it, the notion that bacteria living in your gastro intentional tract can affect your brain sounds rather odd.

There are two ways to manipulate the microbes in the gut: by consuming live cultures of bacteria called probiotics; or by ingesting certain types of sugar molecules, known as prebiotics, that nurture growth of these bacteria. A recent study indicated that consuming a prebiotic bacteria can have an anti-anxiety effect (Schmidt et al., 2014).

The positive influence of the prebiotic was similar to that obtained by taking existing anti-depressant or anti-anxiety drugs.”

Probiotics seem to lower anxiety and mood issues as well. Probiotics are good bacteria that are friendly and helpful organisms that can live in our gut and help our body function better. You can replenish them with homemade yogurt, miso soup (find it in your next japanese meal), kimchi (go korean dining, or buy it in your Asian supermarkets), sauerkraut, and other fermented foods . Our inflammatory response well to probiotics.  A healthy gut flora reduces inflammation. Introduction of probiotics in our gut can have a significant impact in our gastro intentional function and behavior.

Drugs like prozac and lexapro, belongs to a class of drugs call SSRIs, or selective serotonin reuptake inhibitors, designed to affect the neurochemistry of our brains. Intriguingly, 90% of serotonin is produced from the gut. This means, the level of of gut health, has a significant influence on our mental health.

So, the questions remain:

Q1. Will taking care of our gut make us happy?

Yes. I see it as a necessary, but not sufficient factor to take care of. I know that I did not eat well on a given day, it affects my ability to focus, and makes me more irritable that day. Suffice to say that the sample size of N = 1 (me) is not enough to apply to the rest of the human population. There are good studies to suggest that taking care of what we fill our stomachs with impacts our global wellbeing.

Specifically, as we are now learning and beginning to appreciate,  the presence of helpful organisms in the digestive tract, is vital for keeping inflammation under control in the gut.

Q2. Can probiotics replace antidepressant medications?

I don’t think probiotics can replace sound medical & psychological interventions. There is a place for the use of antidepressants, but it does not replace the need for basic nutritional health as well.

Be careful to resist the urge of simple explanations. Certainly, some make benefit from the consumption of prebiotic foods or probiotic supplements, but at this stage in clinical research, there is no affirmative evidence to suggest which particular strain of probiotics that help with with type of mental health concerns.

On the other hand, even the serotonin hypothesis  (you know, when someone tells you that you are depressed because of a neurochemical imbalance?) has been challenged (see the seminal study by Gardner & Boles, 2011). Lets not forget that our dynamic brains are also affected by what we do.

Be mindful of reductionistic thinking.

When in doubt, be sure to consult with your GP or primary treating physician. Ask them about the impact of your gut health and your mental health. Many are actually willing to explain to you if you ask them the right questions. Don’t be afraid to ask them to point you to the right resources or reading materials if you need them.

In conclusion, mounting cutting edge evidence combined with ancient wisdom, it’s not all in the mind.


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Kaplan, B. J., Rucklidge, J. J., Romijn, A., & McLeod, K. (2015). The Emerging Field of Nutritional Mental Health: Inflammation, the Microbiome, Oxidative Stress, and Mitochondrial Function. Clinical Psychological Science, 3(6), 964-980. doi:10.1177/2167702614555413

Schmidt, K., Cowen, P. J., Harmer, C. J., Tzortzis, G., Errington, S., & Burnet, P. W. (2015). Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers. Psychopharmacology (Berl), 232(10), 1793-1801. doi:10.1007/s00213-014-3810-0

Gardner, A., & Boles, R. G. (2011). Beyond the serotonin hypothesis: mitochondria, inflammation and neurodegeneration in major depression and affective spectrum disorders. Prog Neuropsychopharmacol Biol Psychiatry, 35(3), 730-743. doi:10.1016/j.pnpbp.2010.07.030