New research has found that microbes such as those found in probiotic drinks can have a beneficial effect on mental health.
Microbes are organisms too small to be seen without a microscope. Probiotics are live bacteria and yeasts that have beneficial effects on the human body. Such effects include improved gut health and higher immunity. However, only such probiotic drinks that are so certified by the relevant health/food authorities offer such benefits.
Scientists from Duke-NUS Medical School and the National Neuroscience Institute, Singapore have discovered a crucial connection between gut microbes and anxiety-related behaviour. Their research, published here (https://www.embopress.org/doi/full/10.1038/s44321-024-00179-y) suggests that indoles (a kind of organic compound) found in probiotics play a direct role in regulating brain activity linked to anxiety. This could open up new possibilities for probiotic-based therapies to improve mental health.
The prevalence of mental health disorders has been rising over the years. In Singapore, where the study was conducted, one in seven people has experienced a mental health disorder, which includes depressive and anxiety disorders. In 2019, mental health disorders were one of the top four leading causes of disease burden in Singapore. The National Mental Health Survey (NMHS) 2015-16 found that 10.6 per cent of adults in India suffer from mental disorders.
In experiments conducted on mice, the research team found that a germ-free environment in which there is no exposure to live microbes, there is greater anxiety-related behaviour compared with an environment with resident live microbes.
Increased anxiety was associated with heightened activity in a brain region (basolateral amygdala) that is involved in processing emotions such as fear and anxiety. This was further identified to be related to specialised proteins within brain cells known as the calcium dependent SK2 channels, associated with anxiety behaviour. In conditions, when the body and brain are exposed to live microbe metabolites, the SK2 channels act like a clutch, thus preventing neurons from becoming overly excited and firing too frequently.
The implications of these observations are multiple: for example, it opens up the possibility targeting the gut-brain axis to treat anxiety-related disorders by restoring the microbe composition through dietary supplementation with indoles or by introducing indole-producing gut microbes as probiotics.
The team will further explore clinical trials to determine whether indole-based probiotics or supplements can be used in humans as a natural anxiety treatment. If successful, it would open the pathway to keeping gut and mental health in check in one go.