Probiotics to combat mood disorders? You may find such a notion hard to believe but a brand new study has just shown that our gut flora communicates with our brains in unexpected ways. We already knew that bacteria were able to ‘converse’ with the brain by producing the same neurotransmitters as the brain. Now it’s been revealed that they control the expression of numerous host genes via another well-known messenger: nitric oxide.
This discovery confirms probiotics’ huge potential for combatting depression, incidence of which has been growing continuously over recent decades. It also confirms the pioneering approach taken by SuperSmart, with our introduction some months ago of a probiotic formulation called Lactoxira aimed at fighting depression and improving mental health.
Gut bacteria are microorganisms that live in our digestive tract. There are actually trillions of them, which together weigh more than our brains! Originally, researchers believed their role was simply one of aiding digestion. They realised quite quickly that these bacteria were feeding on food particles the body couldn’t digest and were producing beneficial molecules in return. But the researchers didn’t go far enough. In fact, humans exist in total symbiosis with their microbiota, to the extent of creating a human-microbe hybrid where each is essential to the other.
The scientific community thus discovered that gut flora educates the body on how to react appropriately to foreign molecules, and in this way is partly responsible for the maturation of our immune system. The rise in auto-immune diseases in recent decades may therefore be directly linked to a breakdown in our microbiota and impaired maturation of our immune systems.
But the best is yet to come. In recent years, several research teams have discovered that the bacteria in our digestive tract are able to send messages to the brain. Messages that in all likelihood influence a wide range of psychological mechanisms involved in mental problems such as chronic anxiety, depression or mood disorders. Three modes of communication have been identified:
Neurotransmitters are chemicals which are usually released by neurons and are capable of influencing other neurons. It seems that gut bacteria and certain probiotics are able to secrete the same neurotransmitters and send them to the brain via the vagus nerve (this is called the microbiome-gut-brain axis) (1).
For example, several strains of Lactobacilli and Bifidobacteria secrete GABA (2), an inhibitory neurotransmitter, production of which is significantly impaired in cases of depression and anxiety (3). Other bacterial species produce acetylocholine (a neurotransmitter involved in memory, concentration and mood) (4) and serotonin (a tryptophan metabolite involved in controlling mood) (5).
Accordingly, research has shown the use of probiotics to increase levels of certain neurotransmitters in the frontal cortex, so reducing symptoms of depression (6).
In a preliminary study (7) published in December 2018, a six-month period of probiotic administration was shown to improve the condition of people suffering from bipolar disorder. This benefit was greater in individuals with the highest levels of neuro-inflammation. The researchers involved were not surprised: previous studies have shown that probiotics act against inflammation by inhibiting the growth of pathogenic bacteria in the small intestine, strengthening the intestinal barrier, reducing bacterial translocation (8) and decreasing the number of inflammatory cytokines and toxins circulating in the body.
And it’s well-known that neuro-inflammation is directly linked to mood problems(9-11).
A very recent study, published in February 2019 (12), showed gut bacteria are able to control genes via a messenger also used by our cells: nitric oxide (NO).
The scientists behind this remarkable discovery tracked nitric oxide secreted by animal gut bacteria. They found that the NO molecules were completely changing the animals’ ability to regulate their own gene expression. The more the bacteria produced NO, the greater the decline in health of the host.
To restore a healthy balance, the animal would therefore need to prioritise bacteria which do not naturally secrete much NO. In the case of humans, this would either mean modifying the diet in favour of specific foods that nourish good bacteria such as fibre, or directly ingesting bacteria via probiotic supplements, for example.
For some years now, discoveries about gut bacteria have been emerging at an astonishing pace. But it seems there are many more still to come given the complex nature of the interactions between our cells and symbiotic bacteria. What will scientists discover next in terms of modes of communication? Will it one day be possible to measure the precise impact of our gut flora on our health and behaviour? While we await the next developments, probiotic formulations are really taking off. At a time when drug treatments for stress and depression are surrounded by controversy, they offer an unexpected and welcome alternative …
For more information on probiotics and mood problems:
Cepeda, M. S., Katz, E. G., & Blacketer, C. (2017). Microbiome-Gut-Brain Axis: Probiotics and Their Association With Depression. The Journal of Neuropsychiatry and Clinical Neurosciences, 29(1), 39–44. doi:10.1176/appi.neuropsych.15120410
França, K., & Lotti, T. (2017). The gut-brain connection and the use of probiotics for the treatment of depression, anxiety and obsessive-compulsive disorders in dermatology. Dermatologic Therapy, 30(5), e12506. doi:10.1111/dth.12506
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