Butyrates, Gamma-Aminobutyric Acid (GABA) and Prebiotics
Considering the proven benefits of probiotics from these and many more studies the question remains which specific microbes or probiotics may be used as a treatment for mental health conditions? The gut contains millions of bacteria and hundreds of varying strains many of which can not be cultured outside of the body thus proving difficult to isolate and test. Some common probiotics include Bifidobacteria and Lactobacilli, which are widely available as supplements but also easily obtainable through fermented foods, have proven successful in the trials mentioned above but it is believed that prebiotics may have the greater effect. Prebiotics (non-digestible carbohydrates such as galacto-oligosaccharides GOS and fructo-oligosaccharides FOS) act as a source of nutrition for Bifidobacteria and Lactobacilli. FOS and GOS are metabolized and fermented by these microbes within the gastrointestinal tract thus increasing production of Butyrates (a short chain fatty acid, SCFA) and the neurotransmitter gamma-aminobutyric acid (GABA)(7) among others.
Butyrates have a variety of functions in the human body and, specifically for this discussion, they bolster the brain’s natural defenses by preventing breakdown of the blood-brain-barrier(BBB) and promote neurogenesis (production of neurones). This prevents the passage of pathogens and inflammatory molecules into the brain. (14) This supports the theory of probiotics preventing neurodegenerative diseases such as Alzheimer’s(1)
It is not fully understood how gut originated neurotransmitters are able to cross the blood-brain barrier and therefore their direct effect on the brain are inconclusive. Also, reduced levels of GABA in the gut does not necessarily translate as lower levels in the brain. However, the mood altering effects are evidenced through modulation of the HPA axis and through communication with the brain via the vagus nerve.(2) Other studies to support the effect of GABA on mental health have shown that people suffering from depression display altered diversity and composition of gut microbiota (9) with lower levels of GABA compared to people who are not suffering. (8) (10). Which is why GABA producing probiotics are seen as potential treatments for some mental health disorders.
And so, if you’re not already convinced, we have even more reason to introduce fermented foods, yoghurts and prebiotic rice (see recipe) to our plates and even better that the ongoing research points towards a healthy non-pharmacological approach to solving common mental illnesses such as depression and anxiety.