Are you feeling anxious? Can you focus on your work? Are you stable and take your decisions peacefully? There is a bidirectional connection between the gut and the brain. The human gut is filled with more than 100 million nerve cells, more than in the spinal cord or in the peripheral nervous system. Yes, we have brain cells in our large intestines! This explains why antibiotics that disturb the gut microbial ecosystem might cause neuropsychiatric effects, it can also influence your mood and irritable bowel syndrome. Chemicals linked to depression and comfort such as serotonin are also found in the gut; 90 percent of serotonin is made in the digestive tract and not the brain. Many antidepressants work by boosting serotonin. 

The brain is the most complex object in the known creation so how could it be reacting to bacteria in the gut?

• One route is the vagus nerve, it’s an information superhighway connecting the brain and the gut.
• Bacteria break down the fiber in the diet into chemicals called short-chain fatty acids, which can have effects throughout the body.
• The microbiome influences the immune system, which has also been implicated in brain disorders.
• There is even emerging evidence that gut bugs could be using tiny strips of genetic code called microRNAs to alter how DNA works in nerve cells.

There is now a rich vein of research linking germ-free mice with changes in behavior and even the structure of the brain. But their completely sterile upbringing is nothing like the real world. We’re constantly coming into contact with microbes in our environment, none of us are germ-free.