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The 'feeling' gut: Emerging role of gut microbes in mental health

Read time: 2 mins

Our gastrointestinal tract is teeming with a variety of microorganisms. The genes of all these microorganisms are collectively called the gut microbiome. Our unicellular gut tenants participate in our lives by being an integral part of the gut-brain axis—a two-way communication system between the gut and the brain.

We get our microbes from our mothers during childbirth and also through breastmilk. The method of childbirth determines the species of bacteria that will colonise the gut first. These pioneer species of microbes are crucial for healthy growth. Research shows that mice raised without a microbiome have high levels of stress hormones, like corticosterone, and lower amounts of chemicals that help in neurodevelopment.

Our gut microbes also fine-tune the immune system so that it does not turn around to attack them, and yet can fight against pathogens. Babies born through caesarean surgeries tend to suffer more infections while growing up than babies born vaginally. Scientists speculate that during a C-section, microbes from the skin surface enter the gastrointestinal tract. These microbes are unable to coach a baby's immune system to identify friendly bacteria and defend against those that might cause disease.

Studies also show that mice raised in microbe-free environments fare poorly in memory tasks such as identifying a new object and exploring new spaces. Interestingly, these issues can be reduced by transplanting microbes from normal mice into the guts of these mice.

Research shows that disorders such as Alzheimer's, Parkinson's and autism, and stress might be related to the disturbed gut microbiome. It is not yet known if this disturbance is a side effect of the disease, or if it contributes to the illness.

The microbiome can also be used to decrease symptoms of some diseases. For example, patients with drug-resistant epilepsy are sometimes asked to switch to a ketogenic diet to reduce seizures. This high-fat diet encourages the growth of microbial species that reduce the production of neurotransmitters which can help in lowering the frequency of seizures.

The idea of a gut-brain connection is not new. Ayurveda, Traditional Chinese Medicine and Hippocrates have proposed changes in the diet to counter diseases of the mind. However, the mechanism by which food affects our mood was not known then. More research in this area can help us harness the microbiome for better therapeutic use.